Why Physics Favors a Mass Driver Over Heavy Lift Rockets

This presentation, given at ISDC2024 in Los Angeles on May 23rd, 2024, helps to explain why orbital mechanics, engineering, and economics require us to invest in launch infrastructure if we wish to travel to destinations within our solar system beyond low Earth orbit.
The Ascend Paper mentioned in the Q&A section can be found here: arc.aiaa.org/d...
If you'd like to attend ISDC2025, it will be taking place in Orlando, Florida, June 19th-22nd, 2025.
If you are developing a related concept, please consider submitting an abstract to ISDC2025's Interplanetary Infrastructure Session.
More information can be found here: project-atlantis.com

[@dsdy1205]

Next video: Why 5-year VC horizons, 4-year election cycles, zoning laws and airspace management DO NOT favour a mass driver over heavy lift rockets

[@spaceinfrastructure3238]

True - our system stacks the deck in favor of small incremental improvements. It creates a kind of technology hysteresis - but truly disruptive technologies can and will obsolete the old ways of doing things.

[@harbifm766766]

Nothing of that, mass drivers, i.e., a gun or spinlunch inc VC money scam are stupid ideas

[@sjsomething4936]

@@spaceinfrastructure3238 given the possible tie-in between efficiency of launch and also The Boring Company, have to wonder if SpaceX would be interested in expanding their business model.

[@mikegrace8814]

Have you seen Longshot?

[@thefacethatstares]

@@spaceinfrastructure3238 the outer space economy is going to go from 20% of human economic output to 80% in a decade (as in, a decade after it hits 20% at some point)

[@jameshayes2022]

Mathematicians and scientists love their simulations, engineers looking at this thinking what the actual fuck.

[@BlackRedDead1943]

If they just cooperate they could just build, test&experiment and learn from it, until the successrates outweight the risks of failures by enough that pioneers would be willing to risk their lifes on it! ;-)

[@theultimatereductionist7592]

@jameshayes2022 Extremist materialists/anti-intellectuals ridicule the incredible value of mathematical models and simulations. ONLY mathematical models can tell you what-if scenarios for the uncountably infinitely many hypothetical alternatives. ONLY mathematical models can rule out all but a few remaining PRACTICAL models that engineers can then decide to physically test. ONLY mathematical models can test for logical consistency. It's not just abstract law or storytelling.

[@nuttyDesignAndFab]

"we'll just make kilometers of vacuum tube, no problem!"

[@BlackRedDead1943]

​@@nuttyDesignAndFab Actually not that much harder than building that tube in the first place - just a bit challenging, as you would need several pumps along the whole lenght, to create that vacuum in a timely manner! - and ofc you need some sort of Airlock system that closes fast enough before the projectile penetrates the exit membrane, to not have to repeat that process all to often! But it's feasable, i mean we actually build something like that already, just in smaller, for both laser experiments and pretty much every particle Accelerator is a vacuum tube! ;-) (those even require a much more pure Vacuum than a launch tube would!)

[@ZoharEdelkind]

As an engineer, I can tell you that engineers are not (all) thinking 'wtaf'. This type of device is entirely doable. If we can build evacuated particle accelerator tubes tens of kilometers long and massive magnetic field devices to contain plasma during fusion power production (a work still in progress, to be sure), we can certainly build a mass driver with a much less robust vacuum requirement than a particle accelerator and lower magnetic field tolerances than a tokamak. The only real problem standing in the way of building *mass* drivers are *political* and *economic* drivers.

[@augustday9483]

Mass Drivers seem absurdly impractical on Earth, but I do believe they will be a staple of the Moon and Mars. Low gravity + zero/minimal atmosphere changes the equation significantly in favor of mass drivers.

[@omegacsblog]

Agreed. I think the most practical way forward is to put a focus on getting enough mass to the moon to be able to gather water there, then use a mass driver to raise that water to e.g. an L1 station that has enough heat (direct solar, PV, or even nuclear) to split the water (www.energy.gov/eere/fuelcells/hydrogen-production-thermochemical-water-splitting) into hydrolox that can be stockpiled and transported to LEO. We're likely still going to have to use heavy-lift rockets to get to LEO, with methalox being a far better choice than hydrolox when it comes to greenhouse effect, though also ideally using large-scale Sabatier generation of methane even on Earth... However, with large amounts of hydrolox waiting for us in LEO, the other "halfway" gets a lot more practical.

[@theethans898]

As a land surveyor i do stare out the window in awe of the scale of interstate infrastructure as a whole and in a localized manner

[@samuelloomis9714]

I see it as an asphalt desert, but I do marvel at the complex city interchanges.

[@Don.Challenger]

Many (most?) make surreptitious peeks (or more) at their smartphone or the dash display and none of that features the surrounding landscape unfortunately.

[@mylesleggette7520]

@@samuelloomis9714 That's because you're not appreciating the scale of the project, only seeing what you can look at, instead of seeing what lies beyond your vision. It's like looking at a vein under a magnifying glass and not appreciating the complexity of the whole circulatory system.

[@samuelloomis9714]

@mylesleggette7520 The scale that humanity affects things is immense. It honestly gets a little old with how many mega projects there are. Don't get me wrong, each project is a feat on its own. You're asking me to see what I can't. What lies beyond my vision is more asphalt. I believe I shouldn't be marveling at the all so common road, but what takes place on it. I think I should be focusing on the intricate logistical efforts that are going on simultaneously, creating both a delicate masterpiece in the form of organized chaos. What am I on about?

[@theethans898]

@@samuelloomis9714 another layer of even greater complexity!

[@alexanderf8451]

The difference between this and the infrastructure projects you cite is that this doesn't do anything until its finished. Power grids and data cables have been built out by lots of different groups piece by piece. The demand for them is also enormous.

[@spaceinfrastructure3238]

The first undersea cables didn't do anything until they were finished either. They were capital-intensive and probably risky projects. Today, a mass driver can be thoroughly simulated with CAD to help buy down risk before construction begins.

[@alexanderf8451]

@@spaceinfrastructure3238 Building a single undersea cable gets you a thing you can use. But the costs and complexity for a mass driver are more comparable to the whole worldwide network of undersea cables than to a single one. No one would have been willing or able to build out ALL of that at once.

[@migueljoserivera9030]

@@spaceinfrastructure3238 Your counterexample doesn't hold: Undersea cables were a extension of Overland telegraph networks and started by crosing short straits (Dover, Gibraltar...) and even the first Oceanic ones were linking the giant network in Europe to the giant network in North America. I think @alexanderf8451 's argument remains valid. It is expensive and it'll be useless until it is operative. Probably it's best shot is (like with rockets in the 20th century) being useful for the military and having it permeate into civil use afterward. Maybe pitch your idea to some military saying it can be used as an anti-satellite railgun or to deploy space assets within a lower notice.

[@sjsomething4936]

@@migueljoserivera9030 good suggestion to have the military fund it, but my guess is that in a combat scenario militaries would probably find these near useless on earth. They’d be among the first infrastructure targeted and the entire system is an enormous, pretty frail target and 100% stationary. A small explosive making a small hole in any part of the length of the tube (saboteur scenario) or a shock wave from a close proximity large explosion (nukes?) would render it unusable. Despite the lack of any heat bloom, it’s still pretty easy to watch for preparations at the “loading” area (if above ground) and along the entire length of the tube unless as much as possible were buried, and given the expected cost and siting requirements, a country would likely only have a single one.

[@janick01ify]

​@sjsomething4936 It's not just what rhe Rail Gun can do in a war with one of the big guys. You've seen that. While Space X can do it cheap, it can't do extreamly high volume. The military could put so many satilites up in such a short period of time. that it would outlast any system out friend/enemy's could muster. Are we there already?...perhaps, but why not multiply that advantage by another order of magnitude.

[@ctrlaltdebug]

Planetary LEO is cursed. Should be LPO because LEO is specific to Earth.

[@adcraziness1501]

But on other planets it's just low orbit ;p haven't you seen tng? ;p;p;p

[@JamesKelley1]

Low Planet Orbit is not inclusive of Pluto or a moon.

[@jakesto]

Inertially supported structures are ridiculous. The chance of the drive system failing and the whole thing collapsing makes it a risk no sane person would ever take. Even ignoring that, is the cost of generating that much inertia included in the estimate of the mass driver? Propelling a hose into upper earth atmosphere large enough to hold the screws and magnets needed would require a constant baseline supply of power onto which you would add the cost of launching each payload into space. For that matter, the variable pitch screw idea also seems ridiculous. There's only one animation of how it would work in the whole presentation. Going by that animation, the payload is supported by a series of small magnets on the ends of moveable arms that adjust the orientation of the magnets to match the pitch of the screw. The problem with this is that propelling an object forward to reach escape velocity requires very large forces, and assuming magnets strong enough to hold onto the screws are able to fit in such a small space, there would still be enough force on each arm to make robotics a struggle. Now consider the fact that to adjust to the pitch of the screw, the arms need to occasionally pick up their magnet and move it to the other side of the screw. To do this, the arm would need to be able to pull the magnet away from the screw it's holding on to, so the arm would be subjected to even more force! The design in the presentation at least is ridiculous. Maybe a completely different design could utilize a variable pitch screw, but not this one. Despite the exponential costs of sending rockets round-trip to mars and other places, I don't see any other method becoming viable in my lifetime. But please, do your best to prove me wrong.

[@bontrom8]

I was looking for a comment about this. Alignment is so important in any high velocity tube that I know of, and small errors quickly turn into a whipping cascade that would destroy the tube, payload, and anything nearby. The power requirements to keep a tube aligned would be significant. Inertia can't fight large scale relatively slow wind speeds over a long structure. Space launches that are rocket based shake enough from mild atmospheric differences. A tube needs to be aligned to within centimeters I would imagine and even a small breeze at any of the various altitudes would create an immense force. Some sort of counterweight that shifts at a certain frequency plus force engagement at a slower frequency to rebuff the counterweight would be expensive and an engineering nightmare.

[@leocurious9919]

There is a whole lot of jada jada jada in this project with one absurd "solution" chasing the other. A vacuum tube held up by drones... what the actual fuck... the best drones today can not even keep themselves in the air for an hour. Going by DJI FlyCart 30 data, the flight time halves (power consumption doubles) from 29 min to 18 min with 30 kg payload using 2 kWh (drone weight 65 kg). So you want to lift 30 kg payload continuously -> 6.7 kW power needed (200 W/kg payload, 70 W/kg total). How long would the section of vacuum tube be that weighs 30 kg? Lets just say a whole meter. So a km needs 6.7 MW, not even that bad. But that additional weight in power cables... we have not looked into it. Let alone high voltage compatibility. And at sea level with maximum efficiency for the drone. So the classic rocket equation issue all over again, but with cable and less and less efficient drones instead.

[@Shrouded_reaper]

Yes the rational person sees something like spinning hoses stretching from the ground to orbit supporting a giant railgun as a bit dumb. Rockets will do the job just fine scaling size, not throwing away stages and needing minimal maintenance will drop costs to the point where spaces access becomes truly cheap.

[@ResonantFrequency]

That's not really true. Only the coils next to the space craft need to be powered at any given time, the overall power consumption doesn't need to be significantly more than the overall energy in the fuel used in a traditional stage 1 booster. That's still an enormous amount of power but peak load is orders of magnitude less than what you suggest and it's distributed over a long distance and many coils where batteries could be utilized to reduce peak demand. A vehicle like the Saturn 9 had a peak output of 30GW at the booster stage, but we can cut down the weight to less than one third since we're not using a first stage, plus higher efficiency of linear motors vs combustion and spending far less time fighting gravity it could easily get down to 1 GW required, which is about the output of a nuclear power plant. The inertia generated isn't all that bad either, the only inertia is the additional energy being supplied by each coil to the sled and payload, which is overall very small per coil. The coils don't need to sit on screws that can automatically adjust either, we already can electronically alter the magnetic field produced by the coil and use that to make micro adjustments to keep the sled aligned. Over the long term coils could be manually adjusted or done with a robot following the track itself but this could be done more robustly since the changes would be far less frequent. The only part of this proposal that I am skeptical about is creating a vacuum in the tube. That is an enormous volume of air to displace and a ridiculous amount of surface area to seal and it's not even cost, it's simply the engineering feasibility of it. Millions of cubic meters of vacuum assuming 100Kms of track with a 6m diameter and god knows how many KMs of seals between sections, I don't think we have any seal reliable enough to consistently hold a vacuum over that time span.

[@jakesto]

@@ResonantFrequency You seem to misunderstand most of the tech proposed in the video. The video proposes using an inertially supported structure as the launch track. That means the launch tube is being pushed up from the ground on one end and falling back towards it on the other end and then running in a loop back to the first end. The entire launch tube would be moving like a long circular bullet train that goes up into the sky and comes back down. This is what inertially supported means. To keep the structure from falling down, this would have to run 24/7 all the time with no breaks, interruptions, or power fluctuations. This is what would require such an immense amount of energy. The variable pitch screws were chosen in this video because supposedly that propulsion method offers a cost-to-energy relationship on the order of x^2 whereas traditional railguns or coils offer a relationship of x^3. I am criticizing the variable pitch screw idea specifically in my comment, and I don't mention whether coils would be a reasonable solution. I'm actually supportive of a coil-gun space launch system built high-up in the mountains. This makes a lot of sense to me, and it might replace rockets as the preferred way to escape Earth's atmosphere in the next century or two. To your point about how much energy rockets use: Rockets use energy from combustion which is fairly efficient compared to other energy sources. If you wanted to provide the exact same amount of energy to a coil gun or other electromagnetic launcher, you would need to get the electricity from some other form of energy. Every time energy changes form, you lose a significant portion of it. For example, if you burn fossil fuels to heat steam to turn a tubine/generator and store the electricity generated in a battery (chemical energy storage) which you turn back into electricity later, you end up having significantly less energy than the heat energy released by the fossil fuels themselves. Please watch the whole video and read my whole comment before you rebut me next time.

[@bishop8958]

This seemed to have skipped over quite a few significant engineering details. The usefulness of a mass driver depends on A) How much Δv you can get out of it. B) How much of a payload it can launch. Lets look at point A for a moment, due to the nature of how a mass driver works, the velocity of a payload exiting the driver is equal to the Δv the mass driver would provide, since a mass driver can't exert force on an object that's already been fired after all. It takes about 9km/s to get from the surface to LEO, some of that is lost to air resistance, but most of it goes towards actual orbital velocity. If we look at the Space X starship as an example, the lower stage has about 3.6km/s of Δv and the upper stage has about 6.5 km/s, if we assume the mass driver provides only the Δv of the first stage, that means the payload would have to be traveling at 3.6km/s (almost Mach 11) in 1 atm, whihlch would cause serious heating issues, and the payload would still need to have 6km/s on-board just to get to LEO, and increasing the Δv should only amplify the heating problem. Now, you mention building the driver at high altitudes in your lecture, which would reduce your atmospheric pressure, and therefor reduce heating concerns, but the highest point on earth, Mt.Everest still has about .35 atm and very little significant change to Δv required to get to orbit, and considering spacecraft have to deal with reentry heating at pressures significantly lower than that, it likely still won't be nearly enough, and you would have to build significantly higher before you can get any practical amount of Δv out of the mass driver without heating issues, but as you build higher and higher, you start to run into the same issues a space elevator would have with material science being unable to keep up. Along side this, you also need to consider the maximum size and weight a mass driver would be able to sling, if we assume the above problems are somehow solved and we theoretically have a mass driver that can give a 6km/s Δv boost to a payload with minimal interference from the atmosphere, that payload would then need about 3km/s of its own Δv to orbit, and another 4km/s if it wants to go *to* another body *with* aerobraking and no return trip. Just getting that much Δv into a payload small and light enough to fire out of a mass driver would be an undertaking in itself, even with these liberties, the mass driver would be extremely impractical for anything but small probes run on highly efficient engines. By the time we get to the point where we can get significant practical use out of a mass driver on an atmospheric body, we would probably already have better options anyway, and it would make far more sense to relegate mass drivers to non-atmospheric bodies like the moon.

[@spaceinfrastructure3238]

Did you watch the presentation right through to the end? The last third is about the suspended evacuated tube. There's also a good study called "Ablation modeling of electro-magnetic launched projectile for access to space" (funded by the Air Force Office of Scientific Research) which attests to the feasibility of aerodynamics.

[@mileskittman]

@@spaceinfrastructure3238 Listen to yourself talk. The video is proposing to build a rigid vacuum tube that extends to a height of 3 to 6 miles off the ground to prevent the sonic boom from being a problem. The Concord flew at such heights and was permabanned from flying over inhabited land for barely breaking over mach 1, never mind the better part of escape velocity. The above ground portion of the vacuum tube being, by necessity of the extremely high energy projectile within, absolutely rigid, lest even slight deviation from wind in the atmosphere over its considerable length force an energetic and catastrophic interaction between the launch vehicle and the tube. Much like an Alcubierre drive, the math at least appears to check out on a surface level. That is, assuming that you could meet to the requirements to actually build it. Step one, build the thing, is the flaw in this proposal.

The transition from a vacuum to atmosphere besides being like striking a match heat wise would encounter massive physical stresses.. Observe what happens to a high speed rifle bullet when it transitions from air to a fluid..

[@jimwilliams1536]

The only real application is in micro gravity already. mass drivers may be useful for transferring mining products from asteroids or launching from airless bodies or really thin atmospheres like Luna. The issue is always the use of a mass-driver as a possible weapon

[@SteveBrownRacing]

For me it was the hand-waving of 'evacuated tube is easy'.... But vacuum chambers especially large ones are almost never light weight or easy. Additionally, the first part of the presentation was about payload scale. Scaling up payload diameter would exponentially increase cost of the driver just like it does for rockets. And yeah, your points on how to handle the remaining delta V to get the rest of the way to orbit are very valid as well. It's almost like it's easier to do multiple conventional rocket launches and refuel and/or assemble in space.

[@tjthill]

Thing I noticed was, there as no mention of the total size of this thing. Their website shows a model. It needs Google Earth to display it. It's a ring. One side is east of Lake Tahoe. The other side is west of … Brisbane. Australia. They want to build a continuous track that circles the whole Pacific Ocean. Kiiinda guessing maintenance inspections on that, probably going to cost more than the launches save.

[@barrywhite6060]

Not over the long term, yes the costs upfront would be high but the longer it's in operation the cheaper it will get as operations get more efficient and that includes maintenance costs. Most people just can't get past the initial cost to see in the long run it would more than pay for itself.

[@davidrowewtl6811]

​@@barrywhite6060I suspect we would have to take a beating from every other initially cheaper way before we got around to the up front investment required by this way. Maybe if papa Elon got involved, the view might change?

[@equalmc276]

Heavy lift rockets will create the capacity to grow demand sufficiently to justify megaprojects. But even then they won't be a realistic possibility since they are the ultimate soft targets. It would require having a decently inclusive and satisfied society globally.

[@spaceinfrastructure3238]

The Tethered Ring was not suggested as the means of supporting the evacuated tube in this presentation, although it was mentioned in earlier presentations and papers. This presentation was focused on mass drivers.

[@drachefly]

@@spaceinfrastructure3238 Yeah, their comment appears to have been in response to completely the wrong video.

[@simontillson482]

I note a conspicuous absence of any cost estimates for the mass driver system itself. Yes, it might scale better, but what actually is the baseline cost? If it adds up to thousands of times more than a conventional rocket design, then that’s a huge up-front cost hurdle, which would only be economically viable if the system were used thousands of times. Doing only a few launches a year would obviously not satisfy that requirement. Therefore, the main thesis of this project - that of cost reduction - is untenable.

[@spaceinfrastructure3238]

It looks like I'll need to do a follow-up video for people who want to understand and explore the economics.

[@chriscampbell7245]

"support it with drones" - hahahahahhahahahaa I almost sprayed my breakfast all over the screen

[@johnsmithe4656]

I don't care how many DJI agricultural drones you have, you ain't airlifting the Saturn V.

[@PaulBrunson-s3h]

Yeah, he lost all credibility when he said that. Truly stupid idea to support a launch track with drones.

[@Canonfudder]

a glowing rock you can read news off - hahahahahhahahahaa - almost sprayed my breakfast reading that scifi shit

[@tissuepaper9962]

​@@Canonfudder there's a difference between claiming that something is impossible and claiming that it's _prima facie_ stupid. Supporting any kind of infastructure with active propulsion clearly falls into the _prima facie_ stupid category. It would literally be less idiotic to hold up the track with helium balloons, _Up_ style.

[@RocketSurgn_]

@@Canonfudder​​⁠ At the time of tablets (or even just the time of printed paper, far more recently) Computers were unimaginable because of not just new materials needed, or specific technologies (entire categories at that) that didn’t exist but because of entire physics concepts that they didn’t even know existed much less understand well. Mass drivers could (potentially) work on an airless world like getting materials back from the moon but the moment you have an atmosphere you need the evacuated tube reaching through most of the atmosphere part of this concept and you have several huge problems that compound each other. The obvious one is suspending a many miles long tube in the atmosphere, which if you could manage to keep it up with rotor systems (drone, built in, whatever) would burn a LOT of energy that isn’t free… and also a LOT of wear on the lift systems. Heavy lift rotor craft are not cheap and need a lot of maintenance, they aren’t just “drones”. Then the tube has to be flexible enough to change angle when lifted, or orders of magnitude more stiff than materials science can manage to keep it perfectly straight. Then there’s pumping a miles long tube down to vacuum (lots more energy and a LOT of time each time you break the seal) and maintaining that vacuum with inevitable leaks in that large of a system. The spin launch system that claims to spin up a payload in an evacuated chamber can’t even keep one far smaller chamber at vacuum and takes a long time to pump out the air every launch attempt. It’s wildly impractical and the whole concept handwaves all the actual costs/barriers to pretend it’s cheaper than rockets. Innovation is great, speculation on what’s possible is great, but presenting it as cheaper and not addressing the things that makes this at best a very far future solution loses credibility and becomes fan fiction.

[@Pystro]

I have to absolutely reject the statement at 18:36 that the complexity of a dynamically suspended structure would be the same as that of undersea cables. You're talking about something with moving parts (and magnetically suspending those moving parts). Something with at least one vacuum tube (3 if you want separate ones for forward and reverse mass flow and the launch tube). That comes with much greater structural requirements and need to be vacuum-tight rather than water-tight (or "merely" gas-tight). And even worse, the moving parts are inside that vacuum chamber which you can't regularly open for maintenance, so the moving parts have to be designed to last with a guaranteed "virtually zero" failures until they are due for replacement. That's like saying that a highway is "not much more complicated" than a gravel foot path though the forest, since their cross sections look similar except for one or two layers more. Also I don't have the time stamp on where you said it but no, vacuum tubes wouldn't be comparatively light. If they were, we'd have vacuum balloons like the 1800s predicted. In reality, vacuum tubes are as heavier than airplane bodies. (They have to take 1 full atmosphere in the "made-the-titan-sub-implode" direction whereas airplane bodies have to take half an atmosphere in the "self-stabilizing" direction.)

[@rogerwilco2]

Indeed.

[@lrrrruleroftheplanetomicro6881]

With every misfire obliterating the launch complex, while trying to hit the atmosphere at mach 7...

[@MeNanWazaHowitzer]

Good luck pulling a vacuum in that tube and not having any issues when when the vehicle leaves the end of it

The shock and heat would be massive

[@NiteTrain345]

Nice Sci-Fi.

[@Frankey2310]

Yeah, the whole time that bullet was going down the gunbarrel I was thinking: how are they going to prevent the thing from crashing into the wall of athmospheric air at the end? And then he's like: "plasma windows, maaaan". Oh, OK.

@@Frankey2310 Kind of like a Star Trek force field that can keep atmosphere separate from a vacuum?? If we mastered that tech then we would not need this magnetic tube thingy because we could just use that force field to push things into orbit.. I guarantee that there would be a lot of plasma when an object traveling at escape velocity hits atmosphere and it shatters into flaming dust..

[@DavidFRhodes]

definitely redefines 'max Q'

[@recoilrob324]

This proposal is like a Hyper-Loop on steroids....X 1,000,000. So far...the people who have tried to build even a short length of tube...then evacuate it have found it to be VERY hard to do. The velocity proposed for this 'Mass Driver' is many times greater and would require a near perfect vacuum which achieving in such a long tube would be nearly impossible. It's great to dream of 'what if's'...but when they can't be built regardless of the cost....we're stuck with the old 'Rocket Equation' as our only way to space.

[@hgu123454321]

I've worked with large vacuum chambers. Those are still dwarved by this kind of infrastructure, and getting them to a good level of vacuum is incredibly hard, sometimes taking multiple days of work before it seals properly. A hyperloop that has stations with large doors that must open frequently, in my opinion, has no chance whatsoever.

[@Ben31337l]

@@hgu123454321 I was looking for a comment like this. And honestly, you're telling me, every time that door opens, a HUGE wall of air comes rushing through the tube, it would cause massive amounts of G-forces even before even leaving the tube, simply because the vessel acts like a giant piston, pretty much forcing it back down the tube. If you're going to have a near vacuum tube, you're going to need to leave the tube in a near vacuum atmosphere in order to not encounter losses. But even that, the moon will have a significant effect on the atmosphere which would make it inconvenient to launch down a vacuum tube.

[@RePeteAndMe]

Yes, vacuum tubes are currently silly (and might stay that way), but they aren't necessary. A track up a mountain can accelerate a ship as pressure and temperature reduces naturally. You won't match the velocity, but replacing the first stage with electrons while delaying the ignition of any solid rocket boosters can seriously improve the Rocket Equation.

[@SpencerBaum]

​@@hgu123454321I also work with large vacuum chambers, about 5x3x3 feet. To resist deformation the walls have to be multiple inches thick steel, and the whole chamber weighs many tons. It constantly needs multiple high vacuum pumps running just to keep it at UHV. It would be near impossible to scale a UHV chamber to the size needed for this technology

[@Cptn.Viridian]

I am sure numbers wise this works out, but frankly I don't think a single structural or aerospace engineer would be able to watch this presentation without fainting. Having launch infrastructure would definitely be a boon to expanding our space presence, but the scale of such a system is multiple orders of magnitude more intense in scale, complexity, and margins that building it would push our ability to build as a species to it's limit. It's hard enough to build and maintain a length of steel to be straight enough to run a train over it at 200 miles per hour. Maintaining an evacuated cylinder multiple miles in the sky, with the margins to maintain an object going possibly multiple thousands of miles per hour is a task straight out of the worst nightmares of engineers.

[@VEC7ORlt]

I find it quite hard to believe that a mechanical system like screws would be better than plain ol linear motors - electronics is fast and cheap. Dynamic structures are all but a pipe dream for now - supporting launch tube using drones? Oh come on. Building it on the ground or side of a mountain - thats a more realistic proposition. I'd like to see a launch loop based system built someday.

[@utrian4148]

The moment he talks about evacuated tube, I knew this concept doesn't work.

[@sonofbr]

I always thought the "halfway there" quote was referring to technological challenges.

[@ruenvedder5921]

me too…

[@Pystro]

You show the cubic and quadratic curves at 11:35 overlaid with several moon destinations' delta vees. That implies that you can go all the way to those destinations with mass drivers, which you can't. The mass driver can only ever do the "acceleration" portion of the trip: From earth surface to: A) LEO, B) transfer orbit to geostationary or other high orbits, C-E) a hyperbolic escape from earth's gravity directly into a Hohmann transfer orbit (sun-centered) that takes you into the Hilbert sphere of some planet/moon. But you still have to carry fuel (and pay the rocket equation it's dues for): A/B) orbit circularization C) deceleration into a capture by the planet/moon (90% of the full delta-vee if you can aerobrake? Not sure if that discount only applies if you can afford the time to make several passes in and out of the Hilbert sphere) D) deceleration from intercept orbit into a circular low planetary orbit (90% of the full delta-vee if you can aerobrake) E) active braking to get from there to a soft landing. Plus the whole return trip. If you look at the graph at 5:07, the end of the light pink bar is about where the mass driver can get you. The majority of the delta vee still has to come from rockets. Or in other words, the difference between going to LEO and going to Mars and back will still be a factor of 10000 times more expensive. And if you can cut the cost to LEO to 1% of it's current cost, then the cost to Mars and back will also be 1% of the 10 trillion it would cost today (100 billion). But that's still far far from economically viable.

[@sjsomething4936]

Fascinating concept, I would love to see a full feasibility study on this concept given the amount of trouble military contractors have had trying to make pulsed magnet railguns work. Seems like this could be trialled first on the moon to get cargo back off of the lunar surface, all aspects on the moon are better - lower escape velocity, no environmental concerns in terms of affecting the environment or the environment damaging the equipment (severe storms, earthquakes etc), no atmospheric pressure to deal with so no tube needed etc. This concept also means not blasting hundreds of tons of nasty regolith off of the lunar surface to settle on other space infrastructure like habitats. Biggest issue I can foresee is the amount of electrical energy needed in a short time, that infrastructure doesn’t exist on the moon today. Minor concerns of asteroid impacts damaging the system, but that’s extremely unlikely. However, it’d definitely be more of a concern if it were the only way (single point of failure) to get humans off of the lunar surface.

[@jaroslawradecki7166]

Dust might be the real killer of any construction project and machinery on the moon, nevermind a megaproject of those proportions.

[@sjsomething4936]

@@jaroslawradecki7166 dust (regolith) is definitely a problem due to how insanely abrasive it is, but fortunately with no air and no wind or air currents to keep it aloft, it settles back to the surface nearly immediately, and apparently it’s quite freakish to see for exactly that reason. But you’re definitely correct, all sizes of construction projects and basically any human activity involving movement on the moon will face this issue and it is a significant one to resolve if we’re to have any sizeable or permanent presence on the moon.

[@jaroslawradecki7166]

@@sjsomething4936 I'm not sure if the lack of air to suspend the dust particles is a blessing or a curse. If an impact like a foot stomp or a shovel strike gives the dust particles energy to lift off, they will fly in a parabola until gravity brings them back down so you might still see weird dust clouds around a construction site and that's no good for hydraulic actuator seals bushings, power tools and moving joints. Maybe whole site would have to be hosed down with water if the dust isn't totally hydrophobic to clump it together otherwise there's some speculation for electrostatic repulsion, but to implement it for every suit, every piece of machinery won't be easy or cheap.

[@phrozenwun]

Re: Mass stream or dynamic support infrastructure; I have seen plenty of theoretical design work, but outside of (comparatively trivial) things like mass dampers for skyscraper stabilization I have not seen any real implementations of dynamic structural engineering. It would seem that smaller scale design implementations would be a necessary precursor to any practical space infrastructure. Are there any examples of such, planed or working, dynamic support engineering?

[@spaceinfrastructure3238]

Airplanes and helicopters are the closest I think. The fact that so many people are willing to trust them as much as they will trust a bridge or a tall building to support them suggests that the idea of dynamic structures is not fundamentally flawed. I do not know any examples of a structure supported by a magnetically confined mass stream yet, but I also haven't discovered a reason why it would not be possible to engineer such a structure.

[@vincentcleaver1925]

Lofstrom talked about a roughly hundred meter(?) scale model of his launch loop in the analog sf article I read forty years ago, but I'm not aware of him building anything... (Dadada dadada, dididle diedle dee) If I were a wealthy fan! (daaa!)

[@wagnerrp]

@@spaceinfrastructure3238 Nothing lasts forever. Aircraft flights are of limited duration, in between which they undergo maintenance and overhaul. Even if they do happen to fail, you're talking about a relatively small object with a relatively low chance of hitting ground infrastructure, not something hundreds to thousands of kilometers long, weighing millions of tons, traveling faster than orbital velocity. Beyond just the manufacturing of parts and ongoing energy budget, there's an incredible logistical (and even right-of-way) cost at just turning it on or off, and you will need to be able to turn it off to perform maintenance.

[@chrissouthgate4554]

@@spaceinfrastructure3238 If you have the matters Tech to build this mass-driver, would you not also have the Tech to build a Space Elevator?

[@theapexsurvivor9538]

​@@chrissouthgate4554possibly, though more reasonably you have the technology to build a launch loop, which is slightly more practical and safe in an early space expansion context (they tend to collapse more predictably when they have a catastrophic failure than space elevators)

[@SchwuppSchwupp]

The different powers of the launch mass cost and velocity curve are great. I never saw that basic concept.

It is the fantasy space elevator 2.0

[@vincentbrown4926]

I must have missed something. What was the cost of the proposed mass driver? (then, of course, multiply that number by 50 to get the real "built" cost). And what is the proposed cargo capacity? (cost of the mass driver will increase by the cube for more mass) I believe you proposed only a few launches a year, shouldn't you include this "cost per flight" as part of the analysis?

[@spaceinfrastructure3238]

Stay tuned for a link in the description to a cost model which I will post on GitHub in a few days.

[@jakejakeboom]

Minimum $5T USD

[@StephenRWilliams]

Undersea cables were first laid in 1988? Huh? Surely they've been around since shortly after the first telegraph networks.

[@DrVaticinator]

First undersea cable was 1851.

[@deus_ex_machina_]

He must mean fiber-optic cables.

[@bobbabai]

I suspect he's talking about fiber optic cables but isn't actually saying it

[@DrVaticinator]

@@StephenRWilliams yep fiber 1988, according to Wikipedia.

[@mr_obscure_universe]

Alternatives to ponder. Instead of Delta-V as the limiting factor, what about the interplanetary transport network? It’s cheap, but slow. So we’d need self sufficient vessels or habitats, some in cycling orbits. As to the valid concerns about radiation, especially secondary radiation (its German name "Bremsstrahlung"), water is an ideal shield. So our cylindrical spinning space habitat would have its outer most shell filled with water. If that was spun at a maximum of 2 RPM, the radius for 1.05g would be 216m (710ft). The concentric “upper” decks would have incrementally lower g forces. For a lower limit of 0.7g, radius would be 143m (470 ft). If deck height was 10 ft, there could be up to 24 decks. For stability, the ship's length (or height) maximum would be 1060m (3479 ft). There would be a maximum of 27.6 km2 (10.64 sq mi) of deck area, upon which to build numerous habitats, vivariums, and agricultural installations. A giant "rigatoni" in space would be our frugal way to live and travel, surfing gravity. So in that sense, Heinlein was more than correct, if we stipulate the destination orbit is at L4 or L5. For the long view, we might consider building massive self sufficient space stations in high Earth orbit, Lunar orbit, Construction / Launch stations at L4 or L5, and perhaps several Earth- Mars "Cyclers".

[@JasonSmith0]

Thank you for this fascinating discussion. Subscribed. Kerbal Space Program players might add: that first delta-V, in the heavy gravity well and thick atmosphere, brings extra complexity and challenge, compared to subsequent maneuvers in space.

[@whatthefunction9140]

As someone who lives in hawaii I guarantee no one here will ever let you build that.

[@tomusmc1993]

Did H3 ever get built? When I left in the 90s people joked it would never get done.

[@spaceinfrastructure3238]

The people of Hawaii might want their culture to be proportionally represented as humanity spreads out into the solar system. If that's the case, then Monna Kea's altitude and latitude give Hawaii an advantage when it comes to site selection. If they play their cards right, they could control a major gateway from Earth into the solar system. This would be good for the long-term prosperity of their culture, especially if their culture is still fueled by the adventurous spirit of their Polynesian ancestors.

[@kaboomgaming4255]

I think the biggest problem with this is that if a launch goes wrong it'll probably crash straight into Mauna Kea, which happens to be sacred to many in Hawaii. im guessing they wouldn't want to risk that

[@whatthefunction9140]

@spaceinfrastructure3238 I agree but that's not how people here think.

[@NonCredibleDefence]

​@spaceinfrastructure3238 That might be the dumbest thing I've ever heard.

[@nekomakhea9440]

It seems like an AC linear induction motor would be way simpler as a non-pulsed power option to move a sled really fast along a kilometers long track, compared to variable pitch screws. Maglev trains push themselves along using linear electric motors, and the only difference between maglev trains and mass driver launchers is whether there's a ski jump at the end of the line.

[@spaceinfrastructure3238]

The need for pulsed power electronics, and the fact that their cost scales with roughly the cube of the exit velocity, is the reason why mass drivers have historically been considered too expensive. The cost of the variable pitch screw architecture scales with roughly the square if the exit velocity.

[@adrianwilson7536]

I'm guessing a 25 plus multiple difference in projectile speed likely has some impact. Gun powder make bullet fast but adding more of it doesn't keep making bullet faster. You just transition from gun to bomb

[@xehpuk]

I didn't follow entirely but costs need to be divided clearly into development, construction and operational cost. For a mass driver it's also a huge difference if its cargo/fuel only or man rated. As an amateur I believe first step is a hybrid cargo and fuel launcher. It will accelerate at lots of Gs, be only some kilometers long, fire through a simple membrane at modest altitude. Also the cost of delta V is different. Once in orbit ion thrusters or nuclear can be used. Only crew to orbit will need the conventional rockets but we do that already.

[@richdobbs6595]

A mass driver to LEO seems like it is a pie in the sky endeavor until we are already in the Star Trek future. But it seems like you need to factor in mass drivers or spin launch in semi-low earth orbit, on the surface of the moon, on the Mars surface, in Mars orbit, and high earth orbit into your round trip calculations of cost.

[@spaceinfrastructure3238]

I don't think anyone has attempted to do a comparative cost-benefit analysis for mass drivers on the Earth, Moon, Mars, and in orbits around the same. I like this suggestion - thanks!

[@richdobbs6595]

@@spaceinfrastructure3238 Mass drivers on the moon have the obvious advantage that you don't need to have an evacuated tube, and you don't need to elevate them any more than to end at the highest mountain in sight. Mars is almost as good.

[@chrisw1462]

What's going to happen when that vehicle, traveling well over supersonic (hypersonic?) speeds through an evacuated tube, hits the air at the end of the tube? At close to 15 psi? The sudden pressure change alone would challenge the structure. The shock waves would add to that, trying to tear the craft and the end of the tube apart. Then add the g-forces from the sudden deceleration. Even if the craft made it through undamaged (which means it's probably too heavy to reach space economically), could any living being survive it? Unless you want to build that tube to extend into the upper atmosphere, I really don't think this has a chance. Much better to accelerate the air in the tube, then slowly taper sides of the tube wider, slowing down the air gradually until it hits the end at near zero velocity. The supersonic shock wave would be behind them in the tube, and you'd have to deal with more heat buildup, but it wouldn't be like hitting a brick wall at the end of the run. Because, chances are, it Would be the end.

[@thorr18BEM]

15 psi would be sea level. Everest is more like 5 psi. If I'm not mistaken, the video also mentioned possibilities of extending the tube into the air so perhaps even lower than 5 psi in those cases then. From what I gathered, these contemplations are an intermediate step between rockets and space elevators. In my imagination, that puts it very far into the future.

[@drachefly]

@@thorr18BEM Also, you could let the pressure gradually increase as the craft approaches the end of the tube. If you rank the challenges that this faces, this particular one is not high on the list.

[@sdgvlkjnasdlfkjawlk]

Unless there is a PERFECT vacuum the restricted size of the tube will cause air to build in front of the spacecraft. Given the distance and speeds involved here I wouldn't be terribly surprised if exiting the tube into open atmosphere decreased the aerodynamic drag. This could be eliminated by increasing the size of the tube until the sled+launch vehicle act like they're in open space, but that would do insane things to the cost.

[@maxisp1000]

It erodes away to nothing. See cannon launch and spin launch and why they are abandoned, on Earth.

[@8-7-styx94]

As someone who's spent the last 20+ years working on a mass driver conceptually and mathematically. A linear line is not the idea shape for such a device. There's a savings in total material cost in excess of 50% by using either a spiral(golden ratio), or circular design. The screw design is a revelation in this regard but I wonder how well it would transition from a straight shape to one of a curve. Remembering the cost savings involved this could place a large scale mass driver well within reach of the achievable.

[@GornubiusFlux]

I had never heard of a plasma window before this, incredible invention

[@delayed_control]

You've never heard of it because it doesn't exist.

[@GornubiusFlux]

@@delayed_control It does look it up

[@haukur1]

They do exist, but I've only seen very small ones (a few square mm) and only capable of withstanding moderate pressure differentials. Meaning one would need to arrange many of them in series to reach vacuum.

[@gravityawsome]

Good luck getting the funding. Truly.

[@Brooke95482]

See the comments by Thunderfoot on the Hyperloop and the impossibility of pulling a hard vacuum inside the tube because of the high volume of the tube. i.e. it would take a very huge amount of energy and a very large number of vacuum pumps to do it.

[@aberroa1955]

"Cables that did not even exist until 1988" That sounds wrong. Telephone and telegraph lines existed for almost a century at that point. Which isn't all that different from Internet cables. Ballons/drones support: imagine one of them failing, especially the one at the end. And imagine how it would be like trying to scrap remains of whatever you're launching from an area of tens or even hundreds of square kilometers.

[@acasualviewer5861]

Olympus Mons is the perfect place for this

[@TallinuTV]

Any launch plan which involves lighting your rocket engine(s) while the vehicle is already airborne will suffer from one of the same big risks that plagues air-launch systems (where you drop a rocket from a high-flying aircraft). When launching from a fixed mount on the ground, if your engine (or _too many_ engines) fail to ignite, or any other problem occurs which would threaten the success of the launch, you can simply never release the clamps and shut down the engines, and either recycle for another attempt or scrub to investigate the problem, fix it, and try again another day. But if you're already (ahem) _rocketing_ through the sky, you lose that option. If anything but the most minor of problems occurs with the ignition of the engines, you can kiss that rocket goodbye, along with whatever it's carrying. Nobody (aside from Virgin I guess, but that's not orbital class anyway) will want to risk humans on such a system (air launch, rail launch, etc) unless the rocket can be shown to have a 100% success rate across dozens of missions at a minimum. (Multiple engine-out capability would be a big plus there.) And even for cargo or satellites, such systems would still face very stiff competition in the development of fully-reusable heavy launch vehicles and, in time, we'll build that needed off-Earth infrastructure to supply fuel for return trips.

[@jarkkoaitti287]

Have you noticed what spacex rockets do many times a week when they come back?

[@bishopdredd5349]

@@jarkkoaitti287 SpaceX still uses launchpad clamps though, even on Starship.

[@TomLeys]

Plus, all your fuel is free-falling and essentially floating around as blobs inside the fuel tank, just waiting to cause problems on engine start.

[@TomLeys]

@@jarkkoaitti287 Sure, but they light 3 and don't even need 1/2 of one functional engine to land. That's 3x redundancy. On liftoff they need almost all the engines to succeed. It costs more fuel if launch engines fail because you suffer from gravity for longer, meaning engine failures might compromise optional mission objectives. Also for relight the ship is already in a 1G regime - terminal velocity with the engines facing down. This settles the fuel into the bottom of the fuel tanks.

[@terranovarain6570]

We have the structural engineering techniques necessary And launching something into a near orbital trajectory while still haveing full fuel is definitely a win It just takes action and dedication something thats frowned on in this world Hope yall make it

[@HoshoLegacy]

Several kilometers of lightweight evacuated hollow tubing is basically impossible to build with modern technology, certainly not cheap.

I wonder how long the US electricity grid will be the biggest 'machine'? What about the European connected grid, or perhaps the Chinese grid?

[@deathhog]

In terms of size, probably a long time. The U.S. grid spans the entire continent. China has a billion more people, but the communist population solution is to encourage people into the cities more than it is to heavily electrify the villages. This means rather than run a lot of medium and low voltage lines, they can run a few high voltage lines and distribute in city. As for Europe, smaller countries made fairly dense. If the east and the west over connect lines, that's when they would overtake the US grid.

[@littlebigphil]

@@deathhog The US grid isn't even really a single grid, and it doesn't span the entire continent.

[@Quickshot0]

I thought the European grid was actually larger, I thought I'd read it was the largest fully integrated grid lately. And it does span all the way from Portugal to Ukraine. There are a few countries that aren't fully integrated to it in the EU, but most are.

[@danwylie-sears1134]

I don't see square or cube scaling for mass drivers. I see runs-into-a-wall scaling. That's because, if you're going fast enough, running into fifteen pounds of air (or some appreciable fraction thereof -- thumbs-up to drachefly for catching my error) for each square inch of cross-sectional area is indistinguishable from running into a wall. There's a big difference between a very curved pipe thrashing around up in the air and a very straight vacuum tube staying so perfectly still that a payload at orbital speed will absolutely never hit the wall of the tube and convert its kinetic energy into thermal energy quickly enough to convert both payload and tube into incandescent plasma. A mass driver on a launch loop or a space elevator is a really cool idea, but I'm not optimistic. ISRU seems much more promising.

[@drachefly]

They did propose to release at a high altitude where it would not be 15 PSI. The rest… yes.

[@danwylie-sears1134]

@@drachefly Good point.

[@SukacitaYeremia]

Man, Kerbal Space Program enthusiasts are on another planet...

[@JeffreyNaujok]

Mass efficiency is great in naive computations. Until you realize that the "Aerobraking" he talks about at the beginning of the video also impacts the projectile at launch. He also glosses over the fact they need to create a vacuum chamber at a few micro-torr that's hundreds or thousands of kilometers long, and protrudes several dozen times higher than the tallest building ever built, and starting from the top of a mountain that's incredibly difficult to even get supplies to. The cost of an evacuated 16" wide tube like they use at LHC is measured in millions of dollars per meter. Now they want to expand that to many meters in diameter and maintain the same kind of crushing vacuum. Ever seen a rail tanker car pumped down even a few PSI? They collapse like a giant crushed them. Now you want to do the same thing with a tube hundreds of kilometers long. The bracing and steel alone will cost tens of billions of dollars. And the moment you leave the tube, you're going to smack into a Max-Q pressure probably on the order of 100 G. Falcon 9 boosters hit the atmosphere at 40 km and only a few thousand kph and experience 10-12 G of deceleration. And air resistance increases by the Cube. You're coming out of the mass driver tube at 6-8 times the speed the Falcon 9 hits the thin atmosphere at 40 km, so expect 6^3 (216 times) as much deceleration. That's 2000 G. This whole thing is a boondoggle that even first year aerospace students can find the flaws in.

[@spaceinfrastructure3238]

If you divide the cost of the entire LHC project (4.75B) by its circumference (27000m) you get 175,926 $/m. It seems unlikely that the cost of just the 16" evacuated tube is "measured in millions of dollars per meter". That said, I would still encourage you (and everyone) to try to find flaws in the idea by doing the math for real. An earlier video called "Why Don't We Just Launch Rockets With Launch-Assist Infrastructure?" covers some of the concerns you touched on, such as aerodynamic drag and deceleration after exiting the tube. It may be helpful.

[@imflikyt]

You appear to have somewhat glossed over making a several 100km long tube that floats in the air and has objects going through it at ~5km/s

[@wruwruwru]

I have a name for it: a not-so-hyper-loop. It's not complicated. I swear!

[@randomconstructions4513]

OR (and I always choose this one because it's fun and absurd) We drill a half kilometer deep hole a couple meters wide, line it with cement and steel and use about a quarter of the normal fuel for a similar rocket payload to turn it into a heaping great gun. After all, if you can sling a full payload into orbit every thirty minutes or so for near the cost of liquid natural gas and oxygen that's a lot of mass you don't have to stress about putting up there at launch.

[@boradis]

I was such a nerd in freshman college that when I ran for US President in a classroom election I made building one of these a key part of my policy. I won because I was the only one to have a vision for the actual future.

[@spaceinfrastructure3238]

I hope you keep pitching your vision for a brighter future!

[@marklandwehr7604]

How about a mass driver on the moon 1/6th the gravity no Atmosphere Gerald bull left plans for one

[@justin.w.06]

Well unless you can build spacecraft from scratch on the moon, you still have to launch to low earth orbit, so it would be even more costly in terms of delta v cause then theres a moon landing needed in addition to a launch to orbit

[@jogadorjnc]

@@justin.w.06 But you wouldn't need to carry the fuel necessary to go beyond the Moon, which would allow you to bypass issues with the rocket equation

[@eric97909]

I’m not sure why my algorithm recommended this to me, but I am glad it did! I thought this would be talking about rail/coilguns vs rocket weaponry in a sci-fi universe, but it’s still very interesting!

[@jmuench420]

Are you aware of Lofstrom's idea to use launch loop tech to store/transport power? He calls it "Power Loop". It seems to me like a practical way to iterate and monetize the tech in the medium term before having to build a full scale launch loop.

[@brunonikodemski2420]

Our company worked some of these issues, back around the 60's and 70's, along with people like Bull and the Harp program. Those were total and absolute failures. We shot "objects" into local atmosphere at speeds of over 60,000feet-per-second, and the result was that they burned up, just the damaged Space Shuttle coming down, in a matter of few hundreds of feet. UNLESS you can get past the simplistic thermodynamics of air drag, and thermal heating, and Max-Q where the vibrations will shatter you, you will simply burn up, or disintegrate. HARP addressed some of these issues early on, and now we have the California wet-dream of having a vacuum tubed passenger train, running between cities at 500+mph. SO, you could build a tube up, to about 1000,000-feet altitude, to get past Max-Q air buffeting. It would cost a lot. If California had any brains, they would point their tube-rail up into the sky, and launch all of their Wokies out into space. 45-degree angle would work great. Give them token parachutes in case they fall back to the ground.

[@ThatSlowTypingGuy]

So Ecuador (hear me out) there's a couple of places that are *mostly* stable in terms of tectonic action. The question is if there would be enough space west to east for an accelerator to get up to speed?

[@s_cycle1921]

I really liked the presentation. I'd also liked to have seen a cost comparison against what I guess is a reasonably close proxy (give something some inertia, get it high before lighting the rockets) which is Stratolauch.

[@toi_techno]

The SpaceX launch tempo is pretty amazing already Aldrin Cyclers between Earth, Mars and Venus with sizeable populations should be the first mega infrastructure we put in place

[@jsblack02]

100%,. People don't talk about cyclers enough. It's literally a space highway, right there. Let's use it.

[@Shrouded_reaper]

​@@jsblack02Because the Aldrin cycler needs reboosting every orbit. It's a dead end without some kind of propellant free propulsion.

[@pteronoid]

Maybe someone already pointed this out, but LEO means Low Earth Orbit, thus it is not correct to talk about other planets LEO. Similar to apogee and perigee, these terms are exclusive to Earth. The correct terms in this case are LO, apoapsis and periapsis.

[@toddchamberlain6507]

Part 4 is A New Hope

[@jimmy_james0007]

Enjoyed the presentation but would've liked to see a comparison between other space infrastructure such as rockets with ISRU and LEO resupply. Seems like a large oversight considering your talking about space infrastructure.

[@zam6877]

The motivation to spend the money to develop and build the mass driver...comes from the value it makes possible The biggest driver is VALUE CREATED by industry dependent on products, mining, and materials created in space

[@mumblbeebee6546]

Thank you for the insights into the complexities behind space exploration! Given the issues that the native people of Hawaii have with the observatories in Mauna Kea I would warmly suggest dropping that last bit though - it is a great piece of emotive storytelling in itself, but somewhat culturally insensitive…

[@Sgt__Hawk]

Squared or cubed scaling IS exponential scaling. The exponent is 2 or 3 respectively. What is the exponent you compare it to?

[@Lars024_]

If the exponant is constant, i.e. x^2, then it is a polynomial. Exponential means the variable is the exponent, i.e. 2^x.

[@DavidFRhodes]

it seems like SpinLaunch has already encountered some of these challenges, (and failed?). the centrifugal design solves the long tube challenge, as well as suspending the ramp, etc.

[@Quickshot0]

So far I know Spinlaunch is still going for now, but they still seem a long way off from a usable platform and they may never achieve it, yeah.

[@brulez123]

Isn't spin launch a significantly better way to implement this? Get the kinetic velocity in a much smaller area, cheaper and easier to build and deploy. A fleet of spin launchers could even be lifted on blimps and simply land if there is a storm.

[@viscinium]

While the general concept is sound, the things needed to create a functioning and cost-effective version (a huge vacuum tube, very regular launches, support systems, reliable accelerators, etc.) may mean it's something not really feasible at this moment in history - much like how Archimedes could quite easily have been able to calculate that a hundreds of meters long ship with a thick metal hull would indeed float, but such a design would've required tens or hundreds of years of work and the manufacturing power of the entire world at the time.

[@adrianwilson7536]

Yeah, computer simulations are great, as long as you don't have them model reality. You accelerate a space cargo ship to near orbital speed flat on the ground and guess what! It has zero speed away from the earth. ALL its vertical acceleration happens at the curve up! So your frictionless system has to work with the rockets weight times hundreds of g force. The rocket and payload has to handle this. And you want a tube to be lifted into the air. That hast to resist 6 to 7 psi per square inch of crush force, that has to be perfectly held in place, at the side of a mountain and its weather! And it has to deal with the loads breach of the seal and the atmosphere rushing tons of air in at the speed of sound because you are not hanging a massive door that closes in a few millisecond on your suspended pipe. There so much more wrong with this

[@spaceinfrastructure3238]

These are reasonable concerns. To clarify, the forward acceleration on the mass driver and upward acceleration on the ramp in the simulated launch are 80 m/s2, or just over 8 Gs. The suspended evacuated tube external pressure is 60% of one atm at the lowest point but it's down to 12% of 1 atm at its exit. The fast doors will be lightweight and they probably close in around 0.1 sec.

[@hoots187]

fitness beats truth

[@KrazyKaiser]

"It could be built on the Tibetan plateau, India could do it or China could do it" Would be nice if Tibet had a say in it...

[@PotatoShack]

Yeah, that was wild. When he said that, I was thinking "Oof", and he said it so casually.

[@rocksnot952]

This would probably already be a thing, but nations have a problem with what is essentially a huge gun pointed at their territory. Also, what s your tube made of?

[@nicosmind3]

Whenever i spotted this channels name, i knew it would be worth clicking on this video, and instantly subscribing. And the videos barely a minute in and i reckon this will be one of my favourite channels

[@spaceinfrastructure3238]

Thanks!

[@simonjanssen4951]

Helpful infrastructure would truly be a game changer in lowering cost to deep space destinations. I don't think mass drivers are worth focusing on right now as propellant depots would be much more disruptive. We can already send payloads to LEO for relatively cheap, and if the promise of Starship pans out it'll be even cheaper. If you can refuel there, then going anywhere else only costs the fuel plus the propellant depot's profit margins. Once you can make propellant depots, you can also progressively add them in different orbits as you scale up and as the demand manifests. Not to mention, if you add some living space to your depot, it can become a destination in itself.

[@robinpettit7827]

You are halfway to Mars, but you can use gravitational assists to lower the delta-v requirements and yes, aero-braking help quite a bit too.

[@michaelginever732]

Ecuador's Mt Chimborazo. Virtually on the equator and an altitude of 6310 mts. That's 50% greater than Mauna Kea. I agree that ground based energy is terrific because it circumvents the rocket equation. This particular design sounds very promising indeed. At the end of the tube you might use a 'burst disk' something like those spin launch guys are doing. Obviously you need to replace it for each launch and to evacuate the tube again. The air lock idea sounds good but it will have to be able to work very quickly even if the vehicle isn't actually at orbital velocity. And that's another point, if the mass driver "only" accelerates the vehicle to 13,000kms/hr or even 10,000, it will still require so very little fuel and a single vacuum optimized engine. A little like a typical second stage only it will still have plenty of ΔV in the tanks.

[@spaceinfrastructure3238]

I agree. I did look at Mt Chimborazo briefly but I'm worried that it's too steep to support a sufficiently gentle upward curving ramp. But honestly, haven't studied it properly yet.

[@tiggerbiggo]

6:06 I think you were close to choosing the absolute worst colour combination for the lines on that graph, both for accessibility and aesthetics. I had to really really strain to see that there was even another curve on that graph at all since i'm mild deuteranopic. Just throwing it out there, please pay more attention to your graphs. Also my biggest concern with all of this besides what other people have mentioned is the screws. Either those little arms on the side of the cargo have to rearrange themselves constantly to "pull" it along, or the screw, along its entire length, and along a curve, must rotate at an incredibly high speed with no vibration and be free of all imperfections.

[@dizietz]

Is there more details on the screw based propulsion? The paper is not open access and isn't on scihub.

[@spaceinfrastructure3238]

If you're having trouble accessing a published paper, there are versions of the published papers on the project-atlantis.com website. "The Techno-Economic Viability of Actively Supported Structures for Terrestrial Transit and Space Launch" and "The Case for Investing in Infrastructure for Affordable Space Launch" both discuss the concept.

[@Jaggerbush]

This dude is Canadian for sure. 0:15

[@Ligby]

Lmao I couldn’t help but hear it either

[@xthesayuri5756]

So how exactly are you going to build a vacuum tube that is open at one end?

[@Sakkura1]

10:26 The US power grid is smaller than the European power grid. Europe has 523000 kilometers of high-voltage (>110kV) AC lines, more than twice the 240000 kilometers of the US grid.

[@subashchandra9557]

Mass driver + Skyhook? Halve the cost further? It would be pretty sick!

[@PiDsPagePrototypes]

Seems like a lot of technology to develop the thermal protection for launch, and deal with the sudden shock loading of transfer from vacuum tube to atmosphere, when launch systems to LEO are getting more cost effective while avoiding those issues. Would there be advantage to using systems like this in LEO to accelerate the vehicle from orbital velocity to interplanetary speeds? What about mounting it on Luna instead? A ship mounted version for Mining would be incredibly useful in returning ores and ices to locations where those materials will be needed, could the same technology be used to receive and park those payloads? And if so, could it be done without needing the usual Transfer Windows for unmanned payloads?

[@Not.a.bird.Person]

I would like to illustrate a couple engineering issues with this concept : 1. The largest vacuum chamber in the world right now is the Space Power Facility from NASA. This facility costs in the order of hundreds of millions of $ to be built and operate. The Space Power Facility is many orders of magnitude smaller as a vacuum chamber compared to any legitimate mass driver concept. Any mass driver that is kilometers to hundreds of kilometers long would be the equivalent of stacking SPF vacuum chambers on top of each other and a single SPF is only about as high as a couple dozens meters. At best, to reach a single kilometer would likely require a minimum of 20 SPF chamber equivalents. To even reach a single kilometer, let alone many, the costs would be in the order of billions to dozens of billions of dollars and that's not accounting for the thermodynamic inefficiencies of vacuum pumps. Vacuum pumps are extremely inefficient and the higher the volume, the worst the inefficiencies get due to higher potential for leaks scaling with the surface separating the vacuum and the pressurized portion. This is also not accounting for the acceleration systems, only the vaccum architecture. There is a reason why hyperloop concepts and such never go very far and are mostly vaporware, the vacuum alone is likely enough to kill any mass driver concept adopting it. 2. Acceleration and distance is also something that needs to be discussed. Let's say we build a mass driver that does not kill people and we give it an acceleration of 5G since 10G basically makes people faint or die. Through simple kinematics equations, we know that at 5 Gs of acceleration (a modestly uncomfortable ride), a mass driver getting a vehicle to 6km/s would be 370km long. That's the best case scenario for a mass driver with people on board. Reducing Gs will linearly increase time and the length varies by the square of time so we are looking at exponentially increasing length for any less than 5 Gs. On the other hand, increasing acceleration will be more and more uncomfortable for people and likely won't reduce the length enough to make it economical. As discussed above, if 1km costs in the order of even a single billion $ (which is extremely conservative), then hundreds of km would make this cost about as much as the GDP of Denmark before even launching a single vehicle or about 10x the budget of NASA. For every km built, between 5 and 20 launches will occur in terms of current launch cost, that means that to be economical, a 370km long mass driver would need to launch at least (extremely conservatively) 1850 vehicles at the same launch costs as current levels over 5 years with a launch every single day. Dividing launch costs by 2 would mean one launch per day for 10 years and launching once every 2 days at the same costs as today's launch market would also take 10 years to recuperate the investment. Long story short, any metric indicates that to make it more affordable than the current launch market or even equal to it would take an extreme level of use.

[@elliss656]

Once again the sci-fi of my childhood may be a tangible dream. Why did it take 60 years from Fireball-XL5 for anyone to consider this concept?

[@mskiptr]

Could the track for such a mass driver be looped on itself to save on the amount of hardware needed? You would need some kind of mechanism to let the "payload" escape at the right time and place but then it's very similar to that SpinLaunch thingy from a few years back (without such crazy centripetal forces)!

[@TCBYEAHCUZ]

Lofstrom loop is where it's at in my opinion. No need for a plasma window, just raise the launch rail to an altitude that is essentially a vacuum. This eliminates the hydraulic jump that a plasma window entails.

[@tsclly2377]

Yup, the tube launcher came to me on my first visit to the Big Island35 years ago, before surfing with the sharks.

[@SamCyanide]

Because the Massachusetts driver can avoid obstacles and will make better time than anyone else

[@anonymoususer3561]

What if the sentence was about the technological requirements? ("If you can (are able to) get a ship to orbit, you are halfway to the Moon.")

[@littlebigphil]

The problem with that, is that it would be too ambiguous to judge. How does one measure technological progress? Intuitively our rate of technological progress is exponential, but it's not at all clear what the base of that exponent is. What would it mean to double our technological progress? And a halfway measurement requires a beginning point. Do we start at discovering fire or later?

[@YodaWhat]

Many great points are made in this video, BUT use beyond Low Earth Orbit of the MANY alternatives to chemical rockets -- nuclear thermal, ion thrusters, arcjets, even Solar Thermal -- are significant and notable deficiencies. Lacking the full picture, conclusions are reached that don't quite stand up to close scrutiny. Also, some additional benefits of a Mass Driver approach were left out. But this is a good start. It just needs to be WAY longer, in order to cover all the relevant points. IASF videos from Isaac Arthur are tech heavy, yet often exceed 30 minutes, even 40 minutes.

[@wyw876]

"Part 3: A New Hope"? Missed opportunity right here. 😜

[@markdmckenna]

how does the cost equation change when we just add a conventional, non-evacuated, surface built mass driver on an incline as a stage one accelerator? Take a rocket we already know the inner workings of, adjust the design slightly to accommodate the mass driver, then get it up to 500mph or so using a power source it doesn't have to pull along with it. Sure, eliminating exponential cost might be the ultimate goal, but since we're already biting the bullet on exponential, I'd settle for exponential with a higher floor. And then you might start to see incremental investment and development on the mass driver launch system.

[@Jacksirrom]

Will the space cadets ever leave Hawaii alone? Build this psycho boom machine on the continent at the core of the us imperial project!

[@Quickshot0]

While I do agree that mass drivers give some interesting options to potentially reduce launch costs, I do think you're taking the alternatives a bit to lightly in this video. For instance the Falcon 9 is certainly the cheapest option around right now, but it's also obviously being rapidly pushed into obsolescence by SpaceX plan with Starship. Specifically a lot of the current rocket costs aren't in their energy costs, but instead in their one time capital costs. This has an obvious major implication on the cost curves if it can be resolved as SpaceX intends. More specifically it could push prices down by one to two orders of magnitude. And where currently R&D costs for one off beyond Earth orbit missions dominate the costs for such missions, this could then via mass production be driven down far closer to the fuel costs. Of course a substantial capital cost would remain, but it would help reduce the steepness of the exponential curve a fair bit anyway. So if they do actually succeed at that architecture, the prices to beat with a mass driver concept would be far far lower at LEO, and still not all to excessive yet for The Moon and Mars. Beyond that it does seem like the exponential function would start to bite more again. But it would still make the economic case for a mass driver in the short term substantially more difficult as one would need a more mature and cost effective variant to beat the competition. Admittedly with prices dropping that much space activity would probably rise quite a bit and so in the mid term perhaps there would be more interest to explore alternative launch options as the renewable rocket solutions max out what they can do cost wise. Though I do think in the mid term this system will develop yet another challenger which will be a bit problematic. Which would be chemical systems becoming obsolete for in space propulsion. Even now the USA is already developing a nuclear thermal propulsion with twice the ISP that chemical can hope to reach, which would obviously impact the cost curve. But that's really just a side show, the bigger issue is that Fusion power increasingly looks like it is reaching a level where it might become good enough for space propulsion. For instance the CFS SPARC project which is already quite far along in construction is expecting first fusion around 2026 of a standard Tokomak ring design which they hope to get up to a power return eventually of 11. It's torus size is far smaller then for instance the Starship diameter, so in principle if they made it work eventually one could single launch the core of the system in to space in a singular launch. Fusion systems obviously give access to plasma at tens of millions of Kelvin, and thus even if one has to add a fair bit of mass to improve thrust to weight ratios to a reasonable degree would probably give access to very high ISP numbers. Probably starting at thousands and in later generations pushing in to the tens of thousands and maybe even an order of magnitude more. This would mean even early systems might make getting tens of km/s of delta-V far far more affordable then previously and later gens perhaps hundreds to thousands of km/s delta-V. I think it would be pretty hard to create a mass driver that could completely beat the economics of such Fusion rockets if they did come to reach such a level. Even if one built a ring around the Earth, the g limitations for launching objects would probably constrain one to below 100 km/s. Though perhaps this would still be some what competitive in reducing transit times to places like Mars, Venus, Mercury and Jupiter. Still this means that one instead might in the shorter to mid term become stuck trying to defeat the economics of chemical rockets to LEO. Which if they become fully reusable would be a fairly substantial challenge, as likely the Mass driver system might have to start pondering how to recover its launch vehicles as well then. Possible in principle of course, as Starship obviously could do it as well, but still it's a major extra complication to the system. Another issue is that fully reusable wouldn't be the final form of chemical launch systems, I can conceive of at least two further steps they can do to help reduce costs further yet. - One is introducing the recently maturing rotating detonation engine technology. These seem to promise a moderate ISP increase over current engines, I've found it hard to find an exact figure but am guessing for now it might be 10%. While 10% ISP isn't that large a gain of course, it might increase the mass fraction to orbit by a factor of two or so, helping half effective costs again. - The other is that an air breathing first stage should be technologically possible considering how hypersonic technologies are working out lately, especially as those apparently pair well with detonation engine technology which are said to greatly reduce the difficulties of engines able to work at such high speeds. The real gain here is of course that such air breathing engines would have substantially higher effective ISP, which would thus help improve the mass fraction and thus cost picture of the overall rocket. I'll admit I'm not sure how much so though, especially as developing a very large hypersonic air breathing stage would obviously be a very challenging and costly prospect. In any case, these various factors means the kind of numbers one might need to beat to become economic in the mid term might be much harsher then you projected in this video. It may well be possible as you can avoid needing to drag nearly as much fuel up, but there will probably be substantially less margin to work with then one would like.

[@bencheevers6693]

I like this aspirationally it does seem like it's a new take, I'm quite skeptical of the engineering issues but I don't have a doubt that it's physically possible, I just don't have any faith that we're ever going anywhere, like it's possible that humans will never set foot on the moon again much less anywhere else. LEO an unmanned science launches are possibly it for us.

[@FreeRadicalX]

The energy requirements for the screw launcher might not be v^3... But what about the energy requirements for the hypothetical inertial support system? This is certainly something that requires a scaled-down proof of concept before we can start considering seriously, and by scaled-down I still mean necessarily huge. Let's see if we can get something suspended over a kilometer on inertia alone first, and then go from there. I have other misgivings of course but this is the biggest one, literally and figuratively.

[@goldengoat1737]

I want to see the break down on the numbers thats what matters.... Such a great Idea!!!!

[@Aim54Delta]

This certainly has a lot of application once in outer space, as you can more or less slingshot supplies on somewhat regular-ish routes (within the bounds of how orbits work). It works on the Earth, too, but the atmosphere is the main obstacle and the power of acceleration the second. This is not just the physical forces, but the electromagnetic forces likely being used for the purpose. You're looking at field strengths to rival MRI equipment potentially needing to switch at microwave frequencies, creating all manner of interference and induction concerns. The system would almost certainly have to be cavitating in nature with a sacrificial leading edge, or the nature of launch could be shifted to be a ramjet sled which has a far better performance than a rocket and could be returned and reused following a suborbital skip. Ultimately, I think a series of solutions will develop over the coming years. A first stage magnetic power shot which primarily boosts a "plasma jet" (for lack of a better term) carrier into a suborbital trajectory where the jet is capable of using trace gasses for propulsion at much higher specific impulse ratings, which builds the speed for a suborbital hop into which a payload is placed. Of course, if we can do that, why not just fly up there in the first place as we are clearly able to generate large amounts of electricity in a mobile platform... So likely some kind of fusion power or outright magic. A modified 16" naval gun was able to send projectiles into a noteworthy suborbital trajectory, so the problems may not be as bad as some have suggested.

[@spaceinfrastructure3238]

The interference and switching concerns you describe do apply to V^3-type mass drivers such as coil guns and quench guns. It looks like you are quite familiar with some of the challenges associated with those approaches. The variable pitch screw architecture solves the switching problem. If you do go back and rewatch the last third of the video, I'd be interested to learn whether you agree that this architecture is novel enough to merit a re-evaluation of the mass driver approach.

[@adrianwilson7536]

Glad you got to the 'then magic!' Bit all these schemes rely on. We are a steam engine based economy. All our major power runs on steam. It needs lots of water a tons and tons of atmosphere to dump waste heat. We don't have a way to make large compact power systems off world. Battery packs? Still need active cooling at high C loads. Solar doesn't much work past Mars. A lack of atmosphere adds more problems then it solves

[@thecaribbean8615]

Possible advantages of working with the Boring company?

[@Oktokolo]

Does not being able to build "Hyper Loop" vacuum tube rail mean that we also can't build a mass driver?

[@spaceinfrastructure3238]

A vacuum train is a way of making a higher-speed train. It's an idea that may not pencil out from a business perspective since it would cost a lot to construct, operate, and maintain a safe vacuum tube, and its benefit is a small reduction in transit time over a high-speed train. But from a technical perspective, an evacuated tube is a perfectly feasible technology.

[@Gunni1972]

THIS is why fantasies SMOKES finances. Everyday.

[@MatthewElvey]

"Inertially supported active support" is not clearly described/defined. The mass is accelerating - specifically, , presumably gradually changing direction - as it transitions from gaining speed without gaining height to gaining altitude faster and faster as it approaches the tube exit. The reaction is a significant downward force on the part of the tube the mass is going through. How to make a light tube that can handle this varying force is not really discussed at all. Not addressing this massive issue ('scuse the pun) is a glaring omission, IMO.

[@enotdetcelfer]

So basically "ACKhchuAllY" on a catchy turn of phrase, and Hyperloop, because evacuated tubes reaching high speeds like the CGI render has worked just as described so far

[@kampfkeksgeschwa706]

doesnt starship also not have an exponetial cost beacuse of the refueling? And to me sounds easier than building this long vaccum tube. And it would also be interesting to know how the cost of this mass driver would scale with the diamater of the payload?

[@spaceinfrastructure3238]

Refilling is a bit like staging, and staging helps you to get closer to the theoretical limits of the rocket equation. Staging involves dropping some of your mass along the way after it's no longer needed - such how Falcon 9's jettison their fairings. We could also put a fully-fueled-for-Mars Starship into low Earth orbit by building an even bigger two stage rocket with a ~1300 ton payload capacity to LEO. Or we could try to build a smaller reusable rocket with a 40 ton payload capacity to LEO, launch it, and recover it, 1300/40=32.5 times. Either way, the technical challenge is complex and quite costly to execute on.