The tyranny of the rocket equation | Don Pettit | TEDxHouston 2013

[@CharlieTechie]

WOW! One of the best and simplest explanations of why getting off the earth and into space is so difficult I have ever heard. Don Pettit has mastered the Feynman Technique in all its glory. I want to hear more talks from him!

[@danmartinez9497]

It's also the simplest explanation why it is and was impossible to get to the moon or any other make believe place... Space travel is impossible

[@MaxxerG]

I guess you did not perform well in school

[@liamvanenschot6042]

I Dont. Because weird people like you who think their heart and feel with their brain are the reasons why people are still in poverty around the world and bill gates can vaccine everyone and tells he’s for against the world poverty 🤣🤨👀

[@TechNed]

Great talk. The first impression I walk away with is, "space elevator" or unmanned missions.

[@jakemckee2005]

Former, impossible, latter, no fun lol

[@scomacneil2284]

....this is by far the best most informative video on this subject I've seen 🤔

[@GRSG]

Don is an exceptional "out of the box" thinker.

[@TimeLordMe3rd]

Mr. Pettit, YOU ARE FRAK'N AWESOME!!!! I've watched you on the NASA TV channel (on Dish Network: 286, on DirecTV: 352) regularly. YOU invented, designed the latest and, most ergonomic and, functional, 'Space Cup'! My hats off and, much KUDO'S to you Sir!!!! P.s. I personally believe that YOU made a mark in and, will be remembered throughout his/herstory. I'm just say'n. 👽 Adam 🌀 The Sacred Spiral 🐕 Little Bonus 🚀 NASA. Yeah, THAT NASA 💙💙 Time Lord (Me).

[@mattc7939]

SO...if he were to continue with this talk to speak about interstellar travel, you'd quickly find out that not yet invented rocket with 100x the performance of anything we've developed yet, could accelerate to 1% of the speed of light (it would take over 400 years to get to the next star) it would still have to carry 1.68 million pounds of fuel for every pound of dry wieght....which is impossible to build with any material known to man. In short...playing around with the rocket equation you find that interstellar travel using a rocket (i.e. anything that carries the fuel and energy onboard) is impossible. Completely and absurdly impossible. Solar sails are a little better solution theoretically since they don't carry fuel onboard. Solar sails are not subject to the tyranny of the rocket equation. But solar sails have a terminal velocity...which under the most optimistic conditions imaginable (again using sail technology that is on the order of 100 times less massive than any existing material today) (acceleration declines as it exits the solar system)...most calculate a terminal velocity in the range of 0.05% of the speed of light. (150,000 km/s) (which is many times faster than anything ever built by humans)...and this is all using theoretical materials that don't and may never exist. So....unless we figure out a way to contain anti-matter and produce it at a reasonable cost (currently estimated at $250 million could produce 10 milligrams of positrons). Maybe that could actually work...but we don't know how to do that, let alone create a rocket that could harness a reaction based on anti-matter. Ultimately, if you could answer all of these questions, you may find that even if you could harness all the matter in the solar system, all the energy in the solar system, us a theoretical technology build of materials that are 100s of times lighter than anything that exists and still stronger, the furthest you could ever get a pair of humans within their lifetimes, or even several lifetimes (on a generation ship), may only be a few light years away. Ultimately....this may be the answer to the Fermi Paradox

[@danmartinez9497]

Short answer we will never leave earth

[@muzero2642]

I think it is a question of when. Because the technologies are so far off, 2100 is totally unreasonable. I believe it's probably more like 2400-2500.

[@harrypoosie3035]

We can do Anti matter and if we get nuclear fusion we’ll be right there. Also we need to play around with nuclear more, despite its danger. Obv we gotta be careful but to succeed you work with what you have to the best of your ability and right now there’s more banning nuclear then discovering usefulness of nuclear. Pseudoscience.

[@ThomasKundera]

_".this may be the answer to the Fermi Paradox"_ Not really, as it may just be easier to build reliable ships that takes a few tens of thousands years to the next star. The Universe is old enough; what would a few millions years more or less change to an alien exploration of the Galaxy?

[@EtzEchad]

I’m glad he corrected Rocket Scientist to Rocket ENGINEER. Rocket science is easy. It has always been engineering that is hard.

[@jackthelad9933]

I agree. The science is done. It's not really open to interpretation. It's the engineering of something within the scientific constraints that is clever.

[@iliketrains0pwned]

That's the tricky thing about space flight. Sure, there are alternatives that we've looked at (like mass drivers, space elevators, and launch loops). But the key issue is that space agencies and space companies can't afford to try something new. Think about the cost of R&D to make a new launch system from scratch, then testing it over and over again just to make sure it is as close to safe for cargo as it can be; let alone doing _all_ of that again and again just to put a handful of people into space. As crazy as it is that we basically strap a tiny piece of hardware to a skyscraper sized bomb and hope that it makes it, without proper funding, economic support, or Public support it's the best we've got.

[@angelainamarie9656]

Elon's got the problem licked, by designing FOR reusability. The Apollo rockets were designed by people who (originally) built missiles. Of course, they didn't comprehend the idea of getting the vehicle back. Elon is a programmer. He understood immediately the value of re-usable elements.

[@cuscof2]

Not that they didn't comprehend the idea of usability, the technology just didn't exist then. They didn't even have carbon fiber or a 1mhz computer or any number of other technologies that we take for granted today. Just to compute the orbital dynamics of a trip to the moon and back took days of computation time on the biggest computers on the planet. Not a chance that they could have had the boosters land themselves again.

[@fuglbird]

@@cuscof2 The Apollo Guidance Computer (AGC) was a 2 MHz computer. Orbits around the moon and earth were calculated in milliseconds. Composites would not have made a big difference. What made their work impressive was not the navigation but the design and testing of everything using the methods available at the time.

[@warrentaylor8428]

@@angelainamarie9656 If I remember correctly there were originally plans to recover the S1-C (Saturn 5 first stage) using parachutes to lower the stage for an ocean landing, but for reasons I don't recall (that was a LONG time ago!), the plan was scrapped before the first Saturn 5 test flight.

[@shawnschaitel838]

​@@angelainamarie9656 even reusability won't decrease cost as much as you think it it can even doing tons of launches every year unless your doing everything with regards to it in-house and I mean everything including the manufacturing of all the metals and fuel the drilling and making of the fuel so unless he is going to be doing all that as well it may only decrease at most 60-70 % of the cost

[@noahway13]

I don't think it was covered adequately for general public, but the thing that kills the payload, is the fuel needed to go up, is what makes the rocket so heavy. And when you add more payload, you have to add more fuel, both of which add weight. Generally speaking.

[@wedgeantilles7731]

I love this guy!! A true American hero! Thank you sir.

[@jessedampare1379]

This is actually a very eye opening and serious issue.

[@danmartinez9497]

Yeah it should be but don't think the audience picked up what he was saying..

[@CountArtha]

Nuclear fission can give you double the velocity of Hydrolox, with no need to carry oxidizer - that's probably a 600 percent increase in your mass ratio right there. Once we work out how to build a fusion reactor, you could get obscenely fast exhaust velocities and specific impulse.

[@mmicoski]

Very nice and funny presentation on a complex subject! Question: How much fuel is spent from start until clear the launch tower? If during that period the rocket was resuplied, would that be of a noticeable advantage?

[@zockertwins]

Yes, it would be a noticeable advantage. The way you would do this in reality is by adding boosters that you drop a few seconds after launch.

[@trilobyte3851]

its not rocket science...oh wait it is...

[@CombraStudios]

He's right. It's actually rocket engineering.

[@KipIngram]

Heh. Once the company I worked for had a "team building day" and we all visited NASA. One of the sales critters and I were looking at a poster covering some of the basics of rocketry, and he asked some question about it. It's actually fairly simple math and so on, so I, without thinking, said "Well, it's not rocket science..." Then I realized how fun that was, since it LITERALLY WAS. But honestly when you get right down to it, rocket science isn't "rocket science," in the sense of that cliche. It's not that particularly complicated. Everything is clean and easy in space - no air drag, no winds, no anything at all other than simple momentum conservation.

[@MrCalverino]

I LOVE THIS!!!

[@earthbjornnahkaimurrao9542]

great talk, but wish he would have provided answers to his last question. My first thought was launching a rocket from a cargo plane. So you basically make the cargo plane the 1st stage and you remove that part of the rocket equation since you take advantage of the more efficient air travel payload:fuel ratio instead of the rocket payload:fuel ratio.

[@coreysuffield]

you are over looking a significant part of the problem, even if you were to already start in space(Altitude, not orbit) with your rocket you would have barely saved yourself anything, most of the work that is needed is to get up to orbital velocity(side ways velocity, as in traveling parallel to the earth's surface) getting up above the atmosphere barely takes any fuel compared to getting up the orbital speed to stay in space

[@RickeyBowers]

Linear rails seem to be the next technology available to us for launches into space. The difficulty is in constructing and maintaining a sufficiently precise and rugged track.

[@jayyyzeee6409]

Don Pettit is on the record as saying that we destroyed the technology we used to get to the moon.

[@TheEvilmooseofdoom]

The plans for the Saturn V launcher were destroyed. NASA is on record with that. But they didn't need or want it but they did keep some F-1 engines in case they did decide to try something like that again. Since then their main efforts have not been on RP-1 engines but Hydro Lox. That's far from 'destroying the technology' because the launcher was only one cog in the machine the part that only gets you to orbit, not the moon.

[@LeonidsStrapOn]

Jayyy Zeee Why do dipshits think he lies about everything, but take that quote as scripture? ...even though it's completely taken out of context.

[@jayyyzeee6409]

Emmerson Bigguns , Is that all you got? What's your angle?

[@LeonidsStrapOn]

Jayyy Zeee My angle? I'm here to laugh at tinfoil-hat wearing conspiracy theories.

[@TheEvilmooseofdoom]

That's all they are worthy of, pointing and laughing. Fools all.

[@tvs3497]

All of our rocket ships are long cylinders but all of the alien's rocket ships are flat saucer. Are we doing this right?

[@blameyourself4489]

Dude. Rocket ships don't exist.

[@TheSteveSteele]

Blame Yourself You mean alien flying saucers don’t exist.

[@blameyourself4489]

Steve. You're good! I'll give you that.

[@sycodeathman]

Aliens come from a planet with negative atmospheric pressure, so the more frontal area their rockets have the less drag there is at high speed.

[@fakshen1973]

Negative atmospheric pressure? There's no science in your fiction there, son.

[@lachieprice1]

I can't believe how incredulous some of the more misinformed comments on this video are. Honestly it's tempting to sit down and type extended, physically sound responses to all of them, but, alas, as an aerospace engineer I have move important things to do... like design rockets...

[@fuglbird]

But instead you waste your time saying nothing. Interesting. I suppose that is why we buy our rocket engines in Russia.

[@andrewarmstrong8651]

Lachie Price were

[@mosteller1953]

Space crane. Have a station in space with a cable that’s 50miles long ish. The crane can have a ratio of gears, like in normal gear boxes. Lift up a crate. And then a tether from earths ground to the crate. So it keeps it from swaying in the wind. But the space crane would do all the pulling. Space starts around 50-100miles up right? ... I don’t have a degree and I know this could work. I’m just not sure if the station would need to produce thrust in order to stay in space while bringing up all that weight. Probably so, but not nearly as much as we would need for a rocket launch.

[@GeertDelmulle]

This comment section shows proof of the existence of some real weirdos. Still in this day and age. Darwin was an optimist.

[@andie_pants]

Hey! I resemble that remark!

[@slartybarfastb3648]

You MUST make T-shirts and bumper stickers!!! DARWIN WAS AN OPTIMIST. I'd buy them from you in bulk and we'd both die rich. Best bumper sticker ever.

[@andie_pants]

The true KZbin treasure chest: Comments. Some of the finest and most astute human wisdom lies here...

[@andreapedrana9158]

Geert Delmulle

[@life42theuniverse]

Darwin never said anything about mankind getting smarter with time. He stated only that those individuals whom reproduce pass their genes to the next generation ... hence Darwin would say the status quo will outcompete the wierdos and the wierdos will outcompete the brilliant

[@ksmackvolleyball]

Well, there is one concept left out of this video. Spacecraft can be fueled in orbit. For example, you could use 10 rockets to bring fuel up to an orbiting storage base. And then you could fill up your spacecraft using all that stored up fuel. Now you've got a fully fueled rocket already in orbit, that does not have to overcome earth's gravity. First you need an orbiting space station, and then you launch inter-planetary missions from the space station, and not the earth itself.

[@RobKohr]

You still have the tyranny of the rocket equation in space. To go faster, you need more fuel, and that fuel needs fuel, and so on.

[@warrentaylor8428]

That is actually what Spacex plans to do with Starship. Remember that Starship is fully reusable, so even if it takes a number of launches to refuel a Starship heading for, say, the moon, the $ cost should be relatively low.

[@lukefox836]

I have a feeling that was Don's handwriting.

[@gabegeiger9847]

YES KERBAL MAKES YOU UNDERSTAND TINGS!

[@phy29]

Propulsion not so bad if you use inversed walk of mouvement sail ....

[@alectricity3072]

can we just get a big parabolic mirror (10,000 sq meters) and use the energy from the sun(1,000w per sqm) to put a massive amount of energy say (10,000,000 joules per second) into a very small amount of propellant(1 gram per second water)? wont that give semi decent thrust for a reasonable amount of time?

[@tommy2buttz668]

Life is like a box of chocolates

[@mistercreatechannel6947]

Do we have any estimate on what the maximum gravity is for us to be able to send a rocket into space? For example, if intelligent life arose on a planet with five times Earth's mass, would that civilization be able to realistically leave their planet?

[@t.mitchell9135]

No idea, but my maxim has always been that anything is possible given enough time and money.

[@sushantmanandhar1387]

11:15

[@warrentaylor8428]

@@t.mitchell9135 Sorry, that does not include violating the laws of physics and chemistry!

[@df4250]

One thing that is never mentioned is that on earth, locomotion is achieved with the aid of friction and mechanical means. In space, these two factors don't apply - the only one that does is Newton's 3rd law of motion which is for every action, there is an equal and opposite reaction. As we move away from earth's surface, we have to rely more and more on this law of motion. On earth's surface, we can use mechanical as well as friction, which limits our speed somewhat and allows us to have large cargo payloads. In the air, we can use the air to provide some mechanical to lift the airplane's wings, but we have to rely on Newton's 3rd Law for propulsion (for jet engines) which increases our speed capability but increases the fuel payload and reduces cargo payloads. In space, there is no way of mechanical propulsion, distances are enormous so that Newton's 3rd Law is the only means of propulsion, hence the enormous fuel payload and tiny cargo payload.

[@peachent]

DF DF yes, in a nutshell, it can't be done.

[@MaxxerG]

Is it possible to use contrôles nuclear fission or nuclear fusion for thrust?

[@ThomasKundera]

Theoritically yes. And there have been some research on that. Russians may have a working prototype (see 9M730 Burevestnik), but afaik, nothing publicly working exists.

[@gibertusalbans1779]

Earth bound microwaves pushing an object upward has already been thought of.n I do not recall the details or any serious attempts at it though

[@smorrow]

The book Linkers and Loaders by John R Levine has all hand-drawn diagrams

[@chrism.1131]

A new patent I just read about, will allow space elevators to be built with current materials. It has multiple tethers at its center ( for greatest strength ) and fewer tethers as you move away from center ( for lesser amounts of mass ). Liftport has plans to build a Lunar elevator from current material. Using that same material for an Earth based elevator would reach the lunar gravity center (about 9,000 km AGL) approx. 1/6 G. Add this new concept and you could reach Earth's surface. We can do this now. Let's get started. What do you think?

[@crazyspace6792]

Yeah except it’s too expensive and has to be built on the equator.

[@wedgeantilles7731]

Mr. Pettit, thank you and all the teams for your collective heroic deeds! Also...funny how the rocket equation contains the natural exponent.

[@goldfox7116]

The answer for now would be dual purpose fuel, solid fuels in stages, a poly carbonate fuel that once brought into space the remainder of which /unburnt portion could be re-purposed and used as building materials in space. So some burnt piece of solid rocket fuel remnants could be melted down by solar arrays on a space station designed to capture and recycle them and re-purposed into space structures/materials, same with the body and other components of the craft. Then o/c we obviously need to construct a space elevator to use slower more efficient means of transporting high net-weight materials. The problem is tensile strength though, very hard to create a cable strong enough, which means the material needs to be light based (laser propellants a portion of the way) Or we could just make this easy and use nuclear rockets to fly around the solar system with ease.....

[@daniellunsford637]

Gold Fox7 wrong, the answer for now would be to quit trying to launch straight up, as you need more fuel because of the downforce of gravity. Answers to this could be launching low-orbit, or to detach from a large aircraft already at a high altitude.

[@warrentaylor8428]

@@daniellunsford637 As others have already mentioned, altitude accounts for a fairly small portion of the total energy needed to reach orbit, the majority is the energy needed to reach orbital velocity. Remember that kinetic energy is equal to one half of the mass times the velocity SQUARED. It's that "velocity squared" term that is the killer!

[@wesleybarnes5376]

Brilliant.

[@sentzeu]

The rocket equation does not depend on the gravity of the planet launched from. He might have been confused by certain versions of the Tsiolkovski equation that has a g konstant, representing acceleration at the surface of the Earth. But that's there to convert between specific impulse as measured in seconds (1 kilogram of thrust by 1 kilogram of fuel for X amount of seconds) to exhaust velocity. The amount of energy wasted by a rocket as it goes vertical, fighting the gravitational pull is something else and depends ultimately on the thrust to weight ratio of the rocket and its specific trajectory. Typically its on the order of 1 km/s, and drag is usually also around that size. All in all, gravity drag, atmospheric drag and small steering losses combine to make it cost roughly 10 km/s to get into orbit, maybe 9.7. Some of the other numbers are a bit off. You can get to the moon and back on a free return trajectory using 12 km/s.

[@Arkalius80]

You're right, I think he was kind of inappropriately using the term. His point about the gravity was really that Earth's gravity well poses one of the greatest limitations to our ability to go places in space, requiring 8-9k of delta V just to get into orbit

[@FlatOutFE]

The lower the gravity the lower the orbital velocity required. Gravity plays a roll in the horizontal velocity not just the vertical.

[@myster.ejones1306]

Project orion seemed to be differently affected by the rocket equation, maybe because it was a nuclear 'rocket' project worked on by a chap called Freeman Dyson, who was a true Genius in every sense of the word, there's a few documentaries about him, and also on project orion which are surprisingly interesting ☺

[@brian_mcnulty]

I just read this article on NASA's website today. I hope we can do the nuclear thing so that this tyranny does not continue.

[@johnrobinson4445]

Very simple: start a population on the Moon and explore space from there. ;-)

[@321scully]

We've got to get there first ;)

[@MaxxerG]

Elon Musk pan is to have refueling of rockets in orbit. So you send your fuel payload into orbit and refill the next rocket going into orbit to reach mars

[@krishnannarayanan8819]

@@tpstrat14 LOL

[@codyzumr4040]

4:12 *USSR INTENSIFIES*

[@AlJay0032]

That's a very compelling speech for nuclear propulsion, all else is pretty crazy.

[@AlJay0032]

Alternative is to send the energy to the spaceship, for example with lasers and not take it along. Get's hard when you are far away.

[@Talon5Karrde]

This is a prime example why most starship yards are in space in Sci-Fi stories... There was a 2 value divergence between the asteroids and Mars orbit...

[@RobKohr]

The Pettit font needs to be a thing

[@jpdemer5]

One excellent way to escape the tyranny of the equation is to not use rockets, at least not for the early stage of the flight where 80-90% of your propellant gets consumed just to get the other 10-20% partway up. Check out the Stratolaunch - an airplane that gets you to the upper atmosphere, where you can launch a much smaller rocket and still reach orbit.

[@kognak6640]

Upper atmosphere? 10km is not upper. It's just bigger cargo plane, it's not going to "edge" of space. Also it doesn't change the big mean fact you have to accelerate to 8km/s speed to reach orbit around Earth. The carrier has fraction of the needed speed, about 0.2km/s. It's not about altitude, it's all about speed. Btw their cancelled launch vehicle was supposed to have 2.75% payload capacity to LEO(total mass 220t). Soyuz has 2.2%(total mass 305t). They both are ~90% of propellant.

[@greenpeople1775]

The plane doesnt do a lot anyway, the rocket part of the stratolauncher does most of the work, its like taking a rocket to a 10 km mountain top and launching from there, while giving it a tiny kick relative to Orbital Velocity for Earth.

[@UncleKennysPlace]

It's actually better than that, because you can add the carrier plane velocity if you fly in the right direction.

[@TheEvilmooseofdoom]

The brits are working on a engine called the Sabre that is a mix of air breathing and vacuum capable rocket/plane STO concept that looks pretty interesting.

[@notapplicable7292]

The propellant expended by a rocket as it climbs to 10km allows it time at apoapsis to burn horizontally to increase orbital velocity. If a rocket is launched by a plane at 10km it won't have the same vertical speed built up meaning it will need to burn at an angle to account for the lack of vertical velocity causing loss during the longer gravity turn.

[@Whddffddgjfjjf33445]

Great talk, dude explains things with clarity.

[@MrSupercar55]

He calls it propellant. I call it liquid hydrogen. It’s the best damn propellant any rocket nut will ever encounter.

[@smorrow]

What about metallic hydrogen

[@michaeldelarocha8029]

How do I contact Don Pettit? He and I need to talk in person only...

[@h2energynow]

The premise is good, the thought process was weak. Why not change where we are launching rockets off from. The Lecture stated hydrogen oxygen is a possibility for fuel. In near orbit there is hydrogen and oxygen, waiting for us to capture and use for fuel. So change the equation what does it take to launch from space station to MARS, or Moon to Mars, or from high orbit with a fueled rocket to Mars. And what about using gravity, and swing effect of going around the sun to get there faster. Or as science fiction said solar sails.

[@obsoleteprofessor2034]

John D. Clark explained all this in his book Ignition! An informal History of Rocket Propellants..avail free online PDF. It's one hilarious book!

[@fuglbird]

No he did not, but it is an interesting and fun book to read.

[@luisvaladez7832]

if he could do it you can do it for sure

[@mirkono]

A rail gun type launch? It would require enormous area (to handle g forces).

[@ThomasKundera]

It would also need to be incredibly high, not to crash the spaceship on Earth atmosphere. At sea level, density of air limits the max speed to a fraction of what's needed to orbit...

[@ixglocTV]

So if earth's gravity was only sightly higher, we couldn't go to space. But by the narrowest margin we can. I never thought about that. Coincidence, intelligent design or a consequence of the laws of nature?

[@Arkalius80]

That was a bit of a careless statement on his part. The stronger the gravity well, the greater the velocity needed to attain orbit, further complicating the design of rockets. At some point it would make the engineering of orbital rockets using chemical propellants an infeasible engineering problem. It's technically never "impossible", it just gets exponentially harder.

[@ThePOPET1]

Hail Heavy Falcon ROCKET and praise the for the future mighty BFR

[@izzzzzz6]

All hail the air pollution that already is responsible for 4.2 million deaths per year due to stroke, heart disease, lung cancer, acute and chronic respiratory diseases. Wait, hang on a sec, on their site is says 7 million 'Air pollution kills an estimated seven million people worldwide every year. WHO data shows that 9 out of 10 people breathe air that exceeds WHO guideline limits containing high levels of pollutants'

[@phy29]

What about chistofell symbol with lambda=beta and alpha=Mu .....

[@theeye-ns1ch]

how did they manage the weight of a tesla car in a rocket to space?

[@starty8814]

The Tesla Elon launched was a 2008 roadster.The first generation roadster was built on the same chassis as the Lotus Elise. Lotus’s are known for making light sports cars so as a result the 2008 roadster only weighed 1220 kilograms the Falcon Heavy is the rocket they launched it on and it was on a intended trajectory to Mars. The Falcon Heavy can send according to SpaceX 16,800 kg to Mars. Well within the limits of the rocket.

[@tristanmoller9498]

Ways to get around the tyranny? Just use a slingshot duhh

[@tkgwildfire5339]

You have the acceleration problem then. Sending people at or above 30 Gs is not a good idea.

[@JohnSmith-yr6je]

He said 98% of rocket is fuel right?

[@cheneymichael9006]

Exactly. Anyone who was truly listening to his words...he is admitting something...we cannot escape low earth orbit.

[@danmartinez9497]

Simply put we ain't going nowhere and we haven't been anywhere but good ol earth... But as long as NASA keeps getting 20,000,000,000 a year they will keep pushing the space program that hasn't done squat except sprout a few seeds..

[@mixermanbear.4002]

dan martinez Word!

[@ThomasKundera]

@@cheneymichael9006 : _"he is admitting something...we cannot escape low earth orbit."_ No. That's wrong.

[@ThomasKundera]

@@danmartinez9497 : _" we ain't going nowhere and we haven't been anywhere but good ol earth"_ You maybe, but NASA does.

[@pegefounder]

The weight to propellant ratio of hydrogen rockets makes it clear, why SpaceX prefers for the BFR methane.

[@warrentaylor8428]

Not just Spacex, but Blue Origin is using methane for New Glenn, as well as providing their methane engines to ULA for their Vulcan launcher (replacement for the Atlas 5 and Delta 4).

[@bastianschildknecht5133]

What about a very huge trebuchet?

[@Northstar1989]

Technically, the Rocket Equation doesn't give you the mass-fraction of propellant for your rocket, but the ratio of the mass of propellant that you need to have traveling at the speed of the rocket to the mass of the rocket... For a rocket relying purely on internal propellant, these two are identical- but for a rocket that scoops up surrounding atmosphere for additional fuel-mass (an "air-assisted" rocket) these two are not necessarily the same thing... Any rocket that gathers additional propellant as it travels can have an effective propellant mass several times greater than that of the rocket!

[@ThomasKundera]

But space rockets cant.

[@aleksandersuur9475]

Thus the SABRE engine for the Skylon spaceplane concept. However in terms of "when are we going to get it", it's pretty much in the same category as nuclear fusion power plants. And then there is of course the dream of getting at various fuel sources at space to refuel. Ice in polar craters of the Moon, generating methane and oxygen at Mars, launching extra rockets that just carry fuel to orbital fuel depot.. Or, you could greatly increase fuel efficiency, that is going beyond chemical energy for nuclear propulsion, or nuclear electrical at the very least. Various ion drive type of things get fantastic fuel efficiency, but... well... you need outrageous amounts of power for that, or outrageous amounts of time if you rely on solar panels. It's not that we are lacking options exactly, people have been thinking about it and coming up with solutions for a long time, just that none of the options are exactly easy or readily available, or even guaranteed to work. Thus ponying up the budget and time for development is a rather questionable investment. We'll get there eventually, just not as fast as we would like.

[@jeffmartin8106]

Does anyone have a spare dylithium crystal for my warp drive balanced transducer?

[@StevExMachina]

Jeff Martin I do. I take PayPal or Venmo

[@lindvi0r]

I've watched a few videos of this guy, not sure if this is a giant prank or not.

[@einmensch7827]

?

[@danmartinez9497]

The Space Program is a giant prank.. Basically unlimited funding and nothing to show for it except some clowns pretending to float around

[@forksandpopsticles9183]

@@danmartinez9497 no these clowns built gps and a bunch of other sh¡t you use daily

[@بنتأنصار-ح4ذ]

OMG AMAZING!!!

[@taxicabnumber1729]

He didn't even mention the space elevator? :/

[@paulcohen6727]

You're proposing the world's biggest lightning rod.

[@aliensoup2420]

So basically, if you plan to visit a planet larger or more massive than Earth, plan on staying indefinitely.

[@rh323]

I guess you just need to carry less pay load, or perhaps use a more powerful fuel when leaving that planet.

[@ThomasKundera]

@@rh323 : We don't have more powerful fuel. That's the problem.

[@millamulisha]

They gave an astronaut like ten minutes to talk? Wow...

[@aleksa99se]

Something does not add up. If we considered two way trip to Moon and back, what was fuel/payload ratio on return leg of journey? They did not mount additional booster rockets on Moon, or did they? Hint for next presentations: Tyranny of temperature shielding equation. Tyranny of radiation shielding equation. Tyranny of vacuum pressure. Tyranny of live TV feed thru Van Allen belt or Energy requirements for two way TV signal live feed on 238,900 mile distance with two regions of intense radiation partly surrounding the earth at heights of several thousand kilometers. Quite a few titles...

[@peachent]

aleksa99se there's a reason there's no footage.

[@joelmarsman9871]

It’s actually quite simple maths i might be able to explain to you if you really want to know

[@peachent]

Joël Marsman the only problem with your maths is the fact the 'Earth is a closed system, we cannot leave the Earth' as confirmed by Bill Nye. Why can't we leave you may ask? It's simple really, we are decoding an energy field and if we were able to leave that field we wouldn't have anything to decode. Quantum physics has proven this, as has Tesla, Einstein and many others. Nobody has ever been into space, ever, period!

[@marsag3118]

@@peachent I don't know If I despise you more for the "decoding an energy field" non-sense stuff, or more for the fact you place Einstein and Tesla as alleged arguments to your "nobody has ever been into space, ever, period!"

[@peachent]

What is visible light? A frequency. What is sound? A frequency. What did the double slit experiment prove? That everything is a frequency until we decode it. Facts: 1 Mar Sag: 0.

[@galinneall]

At the beginning he kept going on about the exhaust velocity of rockets but completely ignored other factors such as mass flow rate and thrust (or force), which are also important in chemical rockets. And then, based on that, he went on about percentage of propellants. The whole thing left me scratching my head and wondering what he was actually trying to say.

[@Gasman208]

Mass flow is a measure of how fast you empty the rocket, if you want more then you need to carry more fuel and will need more thrust to lift it. Only by increasing exhaust velocity can you improve payload.

[@tracyphillips6485]

That we can't get off of this planet

[@JM-lc3ki]

@@tracyphillips6485 Idrk what you’re talking about, me and you are most likely going to be long gone by the time we reach another star system, but Mars is within our reach.

[@ildefonsogiron4034]

@@tracyphillips6485 Yes sir! And yet, so many people seem to don't get it right. No way to leave the earth with present day technology. Regards.

[@keithmurf426]

Remember, he said that Nasa lost the technology to go Back to the moon.

[@happyagain855]

Life is experience of something you can't get out of alive. Enjoy LIFE instead of waiting your time trying to out smart our CREATOR.

[@tronknows4182]

What's with all these crazy speculations? Stop and listen to what he actually said. "Is there some other way to get off of Earth without using a rocket?" BUT conspiring minds hear "We didn't go to the moon." 😂

[@noahway13]

Idiots hear...

[@1969nitsuga]

TRON KNOWS did we went to the moon? Just the supplys needed exceed the rocket's capabilities...

[@tronknows4182]

1969nitsuga USA, USSR, and China have gone to the moon. As much as the world loves the USA (sarcasm in case you're not aware), I'm sure the whole world would've called us on our bluff if it were not true. I'm open minded and looked into the Moon Hoax conspiracy, but there are too many facts showing that we did indeed go to the moon 🚀 🌙

[@1969nitsuga]

TRON KNOWS my friend... Our current technology does not allow it. All those were mere publicity stunts to promote heliocentrism. Those countries did that to protect money and power of the elites and historical materialism. Who controls the scientific community? Who pays for the experiments and who rule the agencies? Look at Elon Musk, he is profiting from this lie. All is a lie, cgi, camera tricks, fish eye lens and stop motion. Look at Baumgartner's jump, it is the best example. Had you ever seen one rocket up close? Those things filled with high pressure fuels, particularly liquid Oxigen and Hydrogen at many Kpsi. A container to withstand space vacuum of 1x10-6/17 Torr will weigh beyond the rocket's lifting capablities and make impossible for it to carry a useful payload.

[@1969nitsuga]

Edwin Cheesecake space vacuum is 1x10-6 to 1x10-17 Torr. I atm pressurized container will explode if not made like a battle tank. Remember rocket fuel is cryogenic and at high pressures. Vibration and heat will expand it. Even the so called Van Allen Belt radiation can affect that.

[@charlessmyth]

I was thinking that myself, for any greater magnitude of gravity, than what it is. Also, spaceflight via a self-propelled artillery shell, is not a viable option for the future of space travel.

[@evannibbe9375]

Charles Smyth NASA seemed to be considering putting liquid Hydrogen in a rocket and heating it up with fission reactions. However, politics only allows using fission to kill other humans as of right now.

[@zigcorvetti]

nuclear fission or fusion rockets and unmanned exploration.

[@sachinpatwardhan629]

Hooh...so....we can't get there easily

[@MikeM8891]

Put a rocket on a rocket so each rocket only has to accelerate to half of orbital velocity. It would be some sort of two-stage rocket, where as soon as the first rocket is spent it falls away and the second rocket starts. I will take my Nobel Prize in the form a cash, thank you.

[@Marcells44]

... humm yeah that's called staging ^^

[@slartybarfastb3648]

Brilliant! Send Elon a diagram. I'm certain he'll kick himself for not thinking of it himself.

[@evannibbe9375]

It’s a matter of starting higher above the surface (Stratolaunch) and using better propulsion (fission heated liquid hydrogen).

[@a.bergantini4129]

MikeM8891 you joking, right?

[@elkiddo1114]

MorkM8891 dude, done fifty years ago dude, it was called the Apollo Program.

[@saketg5954]

He would go to the moon in a nanosecond and back but he can't because he doesn't have the technology anymore. He used to, but he destroyed that technology and it's a painful process to build it back up.

[@elkiddo1114]

SaketG, Dude, you missed out on a lot of life. The Apollo program was cancelled dude. Most of the hardware was expended (bottom of the ocean, still in space etc), what was left went to museums. That too hard for you to get dude? How long ago was the program? What do you think happened to all of the people? They moved on to other jobs, retired and a lot have passed away. You can resurrect old technologies but the cost is way more than using the modern technology available today. Those old RTL chips haven't been made for 30 years dude. It is a painful process, it is a very complicated project. It requires a new project and that has been started. Orion is ready to start testing. We will soon be back on the moon. Pettit is spot on. You may have comprehension issues dude. I recommend you get your GED and get a clue.

[@saketg5954]

@@elkiddo1114 I love you mexican kid. You open my eyes. Yo no loco no more.

[@elkiddo1114]

@@saketg5954 I love you too dude, Rock on man!!!

[@elkiddo1114]

@@WpgBarry Dude, Pettit was talking to a mixed audience dude., so he spoke accordingly. A lot of the technology was expended, but that term is common. It means a lot of it was used, like the booster at the bottom of the ocean, LEM crashed or still orbiting the moon. It would have been better if he said the technology was "gone". It is, its been fifty years dude, a lot of the technology no longer exists, like the RTL logic used in the computer. That stuff is not coming back. Lots of components were made by expert machinists and other craftsmen that retired or had passed away. You can't just take out the drawings and build another apollo vehicle, and you wouldn't want to do that. You start from scratch as Pettit alludes. Take advantage of today's technology and the data available today. We know way more about the Belts now than we did then. Which is good, cause today's technology is very sensitive and will require a lot of thought to solve. Hoaxer's tend to take very dated material and present it as if it was current. When did Pettit say that? The context is very important. The Orion is being tested now and so if it were recent he would have mentioned that. No doubt that it would be ludicrous today, but it wasn't when Pettit stated that. He could have used better words, I'll concede that.

[@elkiddo1114]

SukitG Dude, What part of that did you not understand? The boosters are at the bottom of the sea, the LEM'sand service module's are crashed on the moon or still orbiting. The capsules are expended, their heatshields are depleted. You can't get the components to build another vehicle, you have to start from scratch and it is a painful process. However Orion is nearly through the process, its already in test. So we will be back to the moon before long. The talk he gave was some time ago and it is correct in that context. That's how you moon hoaxers are, find stuff out of context and claim it to be true, this is the flat earther way. At least something you said was true.

[@josephstalin6549]

*To Pav Phone and everyone shaming the comment section;* if you're going to take all the shitposts in the comment section at face value then you're dellusional to think that KZbin comments determines one's personality.

[@bigdaddylongstroke8326]

Someone explain

[@islandbuoy4]

Donald Roy Pettit (born April 20, 1955) is an American chemical engineer and a NASA astronaut. He is a veteran of two long-duration stays aboard the International Space Station, one space shuttle mission and a six-week expedition to find meteorites in Antarctica. dear sheeple your ignorance will never allow ye to generate the necessary escape velocity

[@islandbuoy4]

ignoramus alert

[@alexs3123]

Archangel Raphael s

[@sentzeu]

Rocket's work better in a vacuum than they do against air. Basic conservation of momentum shows that.

[@after_midnight9592]

Ofcourse there's another way, just ask Lockheed.

[@michaelcooney9368]

Most important essay on space exploration probably ever. Why we never went to the moon, why the cost per pound to orbit has never wavered in 50 years, why we can't go to Mars, why the shuttle failed at safe affordable reusability, why SpaceX besides the hype will only achieve somewhat better cost savings and not huge revolutionary changes. Why it will always be expensive rare and dangerous untill we can get higher ISP or specific impulse without using toxic fission products.

[@ThomasKundera]

_"Why we never went to the moon"_ You or me not, but twelve people in six missions between 1969 and 1972 landed on the Moon. _"why the cost per pound to orbit has never wavered in 50 years"_ Cost per kg to LEO went from $100k to less than $1000 from 1980 to 2020 (source: "Launch costs to low Earth orbit, 1980-2100", in futuretimeline dot net website). Maybe ponder those first before actually asking more

[@michaelcooney9368]

@@ThomasKundera accidentally misspelled, meant Mars not moon.

[@ThomasKundera]

@@michaelcooney9368 : OK, sorry. Then your opinion is worth reading: humanity may never escape the only planet that is suitable for us.

[@michaelcooney9368]

@@ThomasKundera checked the futuretimelines. Some improvement I guess with SpaceX. Still worry there is safety trade-off and cheaper means higher exploding rate. Am not confident especially with manned vehicles that the nature of chemical rocket propulsion means the fatality rate realistic can't get below 0.5%, and explosion/loss of vehicle 2-3 out of every hundred. I just don't see tens of thousands of space tourists on spacex starships especially the whole suborbital hypersonic transport if one out of 50 launches explode and one out of four explosions the crew cabin doesn't survive.

[@ThomasKundera]

@@michaelcooney9368 : I do agree. And to get to this point we harvested lots of non renewable resources and damaged our ecosystem maybe to an unrecoverable point. Maybe the best we'll do in 1000 years is crossing the Atlantic in 2 months... On the other hand, if a semi-autonomous settling can be done on the Moon, from there, departures are way cheaper. Hard to tell were we're going...

[@charlessmyth]

The cold equations of the tyranny of the rocket equation :-)

[@berylrosenberg704]

After 53 seconds; Can we just shorten down to high Delta V rocket engines with 1000+ Isp's are expensive, elusive and politically in their toddler stages?

[@AirborneLRRP]

Could've been done in 4 mins, not 12.

[@justinolson9502]

Rockets are inefficient.

[@udmbfckx2916]

Reaction Engines with their SABRE Design seem to be the only reasonable solution to bring less mass.....Until then, Elon Musk has been able to bring costs down with reusability, damned be all that weight, and it seems he will be able to bring it down even further.

[@berylrosenberg704]

You are pitting an aerodynamic foil that can harness the Bernoulli effect for lift vs a pure explosive rocket thrust and trying to compare?! How about apples to apples? Rocket to rocket. Pulsed nuclear vs Kerosene/O2 etc. This lecture is misleading.

[@flxfaber]

McFLY!?! I THOUGHT I TOLD YOU NEVER TO COME IN HERE!!!

[@KeepinItCrispy]

Felix Faber oh my gosh, he DOES sound exactly like George McFly!

[@peteryuthrayard838]

One way to break the tyranny of the rocket equation is to build plasma propelled aircraft powered by microwaves transmitted from a satellite. It would takeoff from the ground using regular jet engines, go out to sea, pick up microwaves from space, use the energy to super heat air and accelerate it until it reaches hypersonic speeds and the edge of space, then launch the payload into space with an upper stage booster. The energy comes from solar power in space and the accelerated mass comes from the atmosphere.

[@ildefonsogiron4034]

Thanks for putting al those supposed moon missions to rest. Very appreciated 👍

[@ekoms108]

Can't you just make a plane that has the rockets on it too? Or a Hot Air Baloon with rockets on it? Then you could just fly up as high as you can and then engage the rockets.

[@Roxor128]

The hard part of getting into orbit is the speed, not the height. You need to be moving fast enough relative to the ground that it curves away as fast as you fall. Merely getting up high is fairly easy in comparison.

[@goldfox7116]

How to get where you want to go? Your entire rocket must be one with the fuel.

[@jacobrose9606]

had me at propellant

[@shim2dawg]

FOP?

[@jennagentles1836]

I think he said FOB. "Free On Board" It's a shipping term specifying at what point respective obligations, costs, and risk involved in the delivery of goods shift from the seller to the buyer.

[@agee7777]

never mind how they got to the moon, i think it more difficult to get back.

[@izzzzzz6]

Absolutely. I would like to hear his opinion of how much percentage of fuel is needed to leave the moons gravitational pull 30%? I don't see any moon lander's carrying 30% of fuel. Well, i suppose they need only reach moon orbit so as to dock with the main ship right? So, whats that? 20% of it's mass? Perhaps it's feasible but it just seems so unlikely that we can get there with two ships, the lander and the return vehicle / fuel tanks and the fuel for the lander to land and take back off again. One thing that nobody is asking is what effect will 7,000 space x launches have on human health? I mean is the fuel 100% vaporised? There are videos of space x leaving huge clouds in the sky but perhaps this was a malfunction. Still, 7,000 launches by space x alone (perhaps less when they build their mega rocket). Just doesn't feel healthy to me just so some institutions can sell internet to the developing world.

[@schex86]

This guy looks like Marty McFly's dad, sounds like him too.

[@imontirossi]

Don Charlie Pettit

[@David-vn2id]

Was this guy like the smartest kid on the short bus??

[@realityrigged1484]

He's like the Cousin Eddie of the space program.

[@kaselandreas2408]

David 1 he looks like the late Steve Jobs

[@kareemsalessi]

Don Pettit ended with this coded message: “We have NOT been able to fly with rockets, we need to find an alternative”