Deep Space Questions - Episode 12 - Rockets, Science and maybe Rocket Science

[@CraigStuntz]

"Describe the axial distance between the throat and..." -> "I'm not really qualified to answer this." "How common is life in the universe?" -> "I'm not really qualified to answer this." "How would you destroy the moon?" -> "I am the world's expert on destroying the moon. I have simulations of various scenarios at the ready. I also have commentary and simulations on destroying the Earth, just because."

[@doublej1076]

I know it would have been really unlikely, but I was kinda hoping for a GrayStillPlays crossover on that last question.

[@youkofoxy]

Maybe Scott Manley is a active member of that Quora community that has thousands of way to destroy earth. Don't remember the name, just remember that the founder was a physics professor. P.S. found it. Consiglio Devastations.

[@badgerello]

Well it’s certainly easier (and a lot more fun) to simulate destroying the moon in Universal Sandbox than to design the perfect rocket nozzle or answer the question of life in the universe. Trust me; I’ve tried.

[@MonkeyJedi99]

Ooh, the population of the universe is an easy one. From: The Restaurant at the End of the Universe “It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you may meet from time to time are merely the products of a deranged imagination.”

[@chrismiddleton398]

@@doublej1076 And I was hoping for a crossover with The Tic. (In an early comic half the moon is blown off, and it is seen in the sky for the rest of the series.)

[@MrTmac9k]

I remember doing a *very* simplistic nozzle analysis/design back when I took compressible fluids in college. Scott's guess is about what I remember doing -- computing the expansion shocks on the convex part, the compression shocks on the concave part, and then iterating on that until the two cancel out and you have parallel flow at the exit.

[@derMor97]

That's how you end up with ideal nozzles. These are too long (= heavy) for practical use so they get shortened. They are called truncated ideal contour (TIC) nozzles. These do not have axial flow but are close enough. The other type commonly used are parabolic nozzle contours which can be mathematically described by a parabola. They are thrust optimised, meaning that they generate maximum thrust for a given nozzle length. That's why they are referred to as TOC nozzles.

[@MrTmac9k]

@@derMor97 As I said, very simplistic. If I remember right, the ideal nozzle is actually of infinite length.

[@absalomdraconis]

@@MrTmac9k : Infinite indeed, though at some length you'll obviously get declines in the improvements, so somewhere past _that_ you'll have a point where the improvements are too small to bother with.

[@alexhorvath1814]

Check out some of MITs open courses here, the specific method is called the method of characteristics, where you can get the slope of the inside of the nozzle for any axial position

[@MrGoatflakes]

@@alexhorvath1814 ohhh nice. Do you have a link please? 🤔

[@adamdapatsfan]

In terms of SpaceX's ambitions potentially interfering with planetary protection protocols for Mars, I will say that I think it's important to discuss now - not whenever they start flying - because something similar happened with Starlink. SpaceX had spent years talking about a constellation of thousands of satellites, and everyone was kinda like "yeah, sure, eventually, whatever". Then boom - out of nowhere, 60 were in orbit, and _suddenly_ they were interfering with astronomy, seemingly without warning. It's been less than 3 years since the first batch of 60 launched (not counting Tintins), and 1800+ have launched so far. SpaceX is a company that spends years developing things with little fanfare besides Elon's tweets, then _suddenly_ begins to operate them. With a track record like that, it behooves us to get policy questions out of the way early, or else end up _suddenly_ in the middle of a large debate.

[@mrfrenzy.]

Fortunately in a decade or so Spaceship will be able to launch huge telescopes to orbit really cheaply.

[@GreatistheWorld]

Something that makes me conflicted is how the Soviets landed(dropped, crashed) a bunch of things on Mars already, and they didn’t care at all about sterilizing for this problem…so if there’s damage done it’s already been started, or possibly, we could find out what happened

[@jhonbus]

This is a good point, but there's also a big difference between SpaceX suddenly doing a whole lot of something that tons of other companies have been doing for decades, and suddenly doing something that is completely unprecedented. If SpaceX said they were going to send people to Mars in a couple of months, the global scientific community would be justified in telling them to hold up, and the US government would have the power to make SpaceX listen, if required.

[@jamesf333]

@@jhonbus hate to say it buddy, but if you rely on the us current government, I would say they will try to halt spacex progress to the moon and Mars. I believe Elon would be better left to do his own thing. Don’t hold him back, in his lifetime I believe he could potentially change the direction of the human race. If you believe the politicians should control this progress, we have all already lost. Not many Elon musks about to help lead the technological world so far forward. Keep in mind though, musk has said he is only looking to supply the transport means to go to Mars.

[@jhonbus]

@@jamesf333 Well, that's what I was talking about relying on them to do. I think right now it's more scientifically important to preserve any potential Martian biosphere than it is to set up some vanity Mars base. I don't really subscribe to the "Elon is tech Jesus" idea. He's definitely got some great ideas, and the companies he's purchased have achieved some great things. But there's definitely a worrying whiff of megalomania!

[@maxsignori7660]

Concerning Starship: at first, refuelling on ground (@ the tower) was supposed to happen through Superheavy and through the interstage, but this was complicating a lot the design of Superheavy, therefore they have changed strategy. Refuelling on ground will happen through the QD-Arm and supposedly the same QDs on the bare steel side will be used for on-orbit refuelling.

[@surferdude4487]

"... If you don't want to destroy the Earth..." No! You can't destroy the Earth! That's where I keep all of my stuff.

[@kittty2005]

An old family friend and I were talking about engines and fuel. He was a retired lieutenant commander in the U.S. Airforce engineering division he was in the unit that tested, I wish I could remember his name, possible fuels and engine types for space flight. They were working on fuel combinations ,their test engine at the time was a F-4 engine and he said that just jet fuel the engine produced 30,000 HP, with a combination of furfuryl alcohol and aniline oil and hydrazine the engine would produce 130,000 HP . They, his team were seeing if a conventional jet engine could hold together long enough and produce enough power to briefly go to space, He said no the engine they tested would soon fly apart and a turbojet engine relied heavily on ,not only expanding combustion gasses but heated atmosphere ,once in space all you have is combustion gasses and no air intake and the turbojet is very inefficient in that regard, he was no dummy he was aware that the atmosphere extended quite a distance from where humans can survive unaided, but he was helping to design the X-15 engine system, that's all I remember him saying. He was in his 70's I think. I was in my mid 30's, so it's been awhile.

[@MrTurboTash]

19:38 It was at this point I realise, Scott has already done the calculations on building an IRL Death-Star... *Manhattan project shivers down my spine*

[@NefariousKoel]

Regarding radar use on landing, I imagine it would be at least an altitude radar in the rocket so that it knows when to lower the landing gear and increase it's thrust at the right time just before touching down.

[@johndododoe1411]

With Elons _current_ design philosophy, putting as much equipment as possible on the ground and simply use short distance radio to command the steps of the landing process would be the obvious solution. But lightweight ground proximity radar is standard commercial equipment, so could be installed on F9.

[@dannywhite648]

12:07 that was unexpected funny, ibx is initialism so the letters are pronounced individually. he is a Minecraft KZbinr notable for playing on a bedrock edition (instead of Java).no idea why someone thought you were watching him. I guess your intros of hello it's blank here are similar

[@osman9750]

I think he also does geography videos maybe somebody thought they saw something similar there.

[@adjacent819]

Yeah I was thinking why on earth would Scott watch toycat

[@ericgulseth74]

@@osman9750 Yeah, his geography videos is what I know him for. Only thing I can imagine they share is an accent, but I don't know where specifically they are both from originally from

[@Back_Fire2468]

the launch tower kinda looks like the sugarcane farm. But I think I might be reaching

[@HOOOPER]

Given the excessive use of commas I'd say it's just a kid that doesn't understand KZbin. Although if that's the case idk how he made a patron account.

[@41istair]

Inspired by the Dart animation, can you produce a technical feature on exactly how various solar array deployment mechanisms work and the engineering associated with those actuators; whether they powered, sprung, retractable in space, etc?

[@ColdWarAviator]

Scott, I was stationed on the Central Coast in the late 80's at Fort Ord. It's no longer there as they decommissioned the Army base in the Early 90s, but it's a beautiful area. If you get a chance, head down to Monterey and go to the Monterrey Bay Aquarium. While I was there they were filming Star Trek IV the voyage home... The one with the whales... But seriously it's the only aquarium I know of that has a display where you stand and look through plexiglass and have the actual Pacific Ocean on the other side of the glass, so you see real time oceanic action and not a closed ecosystem in a tank. Also The old Fisherman's What has the best Chowder and Seafood around if you like seafood. Lastly, Carmel and 17 mile drive are just down the road from Monterey (15 minute drive) , beautiful scenery. And awesome place to watch the sunset. Drive Safe.

[@Markle2k]

It is still there. It has been repurposed, much like The Presidio, Treasure Island, NAS Alameda. Like those, it’s actually more accessible nowadays.

[@ColdWarAviator]

@@Markle2k yeah the land is still there.. I know they didn't cut it up i and take it away... Except probably some of the firing range on the bay behind what used to be Stillwell Hall, but the old barracks are in disrepair and the college is most of the bigger buildings which were brigade and squadron headquarters buildings.

[@Markle2k]

@@ColdWarAviator I wasn't saying that you thought the land fell off into the sea. In essence, I was bolstering your recommendation for a visit because it is more accessible than before. I mentioned the places I did because Scott is well familiar with them since he lived in Oakland before moving across the Bay Bridge to SF. I could have added Mather and McClellan as well where the military infrastructure was repurposed for civilian use. It is interesting that you mention "Stilwell" Hall because I went to a UC and there seem to be prominent buildings named after him on a lot of campuses.

[@model7374]

Isn’t the coast hiway closed due to an earthquake or mudslide or brush fires or some other californicaion disaster

[@ColdWarAviator]

@@ChadDidNothingWrong well Clinton was bound and determined to dismantle the military... And he tried... But no dice. As far as why they chose to close the base: if you close Fort Ord, then you can turn it intoa federal park with two miles of beaches and then create additional government jobs for Park rangers, and charge admission to the Park, and all sorts of Big government things. Plus the land that they used to have base housing on probably sold for about 250K per acre... As well as the houses which were nice. It's a money thing.

[@crewleader3834]

Hey, finally a question I can somewhat answer. As part of my bachelor group thesis I worked on an Air-Breathing Electrostatic Spacecraft with ESA. The spacecraft orbited at an altitude range of 200-250 km, which I should note is just a ballpark figure as calculating the "collection efficiency" of a funnel in near vacuum conditions was not really part of our bachelor curriculum so plenty of assumptions where made. Additionally flying lower is also possible but the power and thus solar panel surface area would quickly increase. To answer your question wherever such a spacecraft could orbit at the same altitude as olympus mons on mars the short answer is: No. The air density on Earth at 200-250 km range is about 1e-10 while on Mars the density at 20km roughly the altitude of olympus mons is about 3e-3 a difference in density by a factor of a couple billion. The required amount of power and thus solar panels would be ridiculous. I should note that plenty of research is required before such an idea (at a more reasonable altitude) can be remotely feasible namely in corrosion and collection efficiency.

[@mapesdhs597]

Thanks for the summary! May I ask, are you aware of much if anything in the way of novel tech for better solar panels? In the past, mags like New Scientist and Scientific American would report on such things, but materials cited in research labs just never seemed to make it to the commercial market (which more or less applies to just about every tech field). I suppose one problem with solar is availability of materials, many of the required elements coming from shall we say the less savoury parts of the world, or those where political tensions may result in the future complications of supply.

[@crewleader3834]

@@mapesdhs597 I am not an expert on solar panels by any means, I know that there have been significant developments in the efficiency of solar panels but the reason why they have not trickled down to consumers can be caused by many issues (material rarity, manufacturing complexity, economies of scale, etc...). At the end of the day a solar panel developed for a space mission is significantly different to a commercial solar panel. Regarding novel tech for better solar panels, there is a lot of focus on improving the reliability and deployment of solar panels rather than just focusing on pure performance, for example using rollable solar panels to improve packaging and deployment.

[@mapesdhs597]

@@crewleader3834 Good points about deployment and reliability, likewise the different conditions they must tolerate. Presumably weight matters aswell. Thanks for the reply!!

[@davidbooth8422]

About transferring fuel in space, wouldn't they want to use the same interface ports as the tower arm uses?

[@kstaxman2]

That's just what he said is the current plan.

[@tevvya]

On the question of the rareness of life. The question is better couched, IMHO, as "How likely are we to discover life elsewhere?" Now that is a basis of three axes: 1. The density of life-supporting bodies, 2 The distance that one could travel and stay in touch with some of the rest of humanity and 3. How long humanity will continue to exist. Density, distance, and time. If you have good estimates on each of those you will have your answer.

[@fishea]

‘Transferring cryogenic propellants in space… is not something that has been done before‘ DOGG HAVE YOU SEEN SPACECAMP, THE MOVIE??

[@ale131296]

For the rada question for F9: F9 does have a radar altimeter on the octaweb that uses to precisely time the landing burn and be able to tell how far from the ground it is and the throttle setting it needs on the landing engine

[@jgottula]

Yep, F9 definitely uses an onboard radar for landing purposes. My brother used to work at SpaceX, and I believe at one point he was working specifically on the radar altimeter.

[@2424Lars]

On the periods between planetary flybys: Mariner 10 - Venus Flyby 5 Feb 1974 - Mercury Flyby 29 March 1974: 52 days Parker Solar Probe - Launched 12 August 2018 - Venus Flyby 3 Oct 2018: 52 days Bepicolombo - Venus Flyby 10 Aug 2021 - Mercury Flyby 1 Oct 2021: 52 days All three transits are tied for shortest in terms of days

[@Релёкс84]

It's almost as if the motion of planets were periodic and predictable

[@2424Lars]

@@Релёкс84 It's still an incredible coincidence considering the high eccentricity of Mercury's orbit, as well as the unusually high characteristic energy of Parker's launch.

[@garthnareng4898]

The web page for that ion engine talked about using "space air" which always makes me laugh.

[@jtjames79]

Another reason the Karmen line is basically useless, for anyone but lawyers.

[@absalomdraconis]

@@jtjames79 : The Karmen line isn't useless, just _very very limited_ in it's uses. In particular, the _real_ Karmen line is where orbital velocity & aerodynamic lift velocity are equal- any higher, and you have to go _faster_ for lift to work than the orbital velocity at that same height, while the opposite holds true _below_ that height. So, for the very narrow purpose of defining the edge of "outer space", the Karmen line is quite useful.

[@jtjames79]

@@absalomdraconis what planet are you from where "basically useless" and of "very little use" is a distinction with a difference?

[@NarwahlGaming]

Perhaps they can use 'Perri-Air'. [Spaceballs reference]

[@sulljoh1]

Gah! Space air is flooding in! Goggles on!

[@3gunslingers]

About fuel transfer between two Starships: They will likely use ullage thrusters just to settle the fuel to the end of the tank and then they will use the immense pressure difference between the ships to actually transfer the fuel. Starship needs a tank pressure of about *6 bar* for the Raptors to operate optimally. This pressure will be used to push the fuel, while the receiving ship will vent its tanks against the vacuum of space. With this system the orientation of the receiving ship is not so important. They can dock side by side or butt to butt, doesn't matter. The location of the fueling ports becomes more interesting.

[@stuartgray5877]

I always thought they should be able to mate nose to nose then spin. This would give both starships "artificial gravity" and settle the liquids to the same point they are on the ground.

[@3gunslingers]

@@stuartgray5877 And then you have to build pipes all the way up to the nose to transfer the fuel. You also need to make a hatch in the heat shield of the nose for docking. And you have to relocate the header tank from the nose to somewhere else. I don't think SpaceX wants that kind of hassle. The will dock butt to butt or side to side. Much less development and hardware needed.

[@stuartgray5877]

@@3gunslingers the starships already HAVE plumbing to the nose. That's where the secondary landing tanks are.

[@3gunslingers]

@@stuartgray5877 Only for oxygen. The methane header tank is between the main tanks. And you still have to answer the question about docking.

[@l.merbecks8144]

Re: Nozzle Design I remember my professor for fluid mechanics mentioning that there is a way too solve the differential equation for the nozzle area via the methods of characteristics i.e. you get a function area vs distance. This solution, however, would be an ideal solution, I guess, so iteration would be necessary. Stay tuned maybe someday I will return wiser…

[@massimobattaglia5093]

I remember it was obtained by including the condition that the expansion should be isentropic but it was a long time ago . ...

[@KX36]

To get a practical solution, take the ideal solution and divide by root 2. Makes no sense but people will think you know what you're talking about. At least that's what I do in electronics.

[@2424Lars]

Luckily, taking a straight nozzle with a ~15 degree half-cone angle will get you about 98% efficiency as compared to an ideal 'bell' nozzle. Bell nozzles are shorter however and therefore they weigh less than straight conic nozzles, so it's usually a trade-off between mass and manufacturing complexity.

[@jeremiahchamberlin78]

Nozzle length is determined by the ideal nozzle shape that give flow 100% in the direction of travel. The shape (length/geometry/etc.) of the nozzle is derived theoretically and is based on expansion angles and compression angles. The real shape accounts for boundary layers that have the effect of shrinking the real diameter of the nozzle.

[@Markle2k]

Are the shapes going to differ based upon propellant properties or efficiency of combustion? i.e. velocity and molar weight.

[@jeremiahchamberlin78]

@@Markle2k the shape depends on the ratio of chamber pressure to exit pressure.

[@kevinkorenke3569]

So like Jeff Goldblum says: "Life, uh, finds a way."

[@vmasing1965]

Yes, once it exists, it finds a way. The real problem we currently have is, nobody knows how the simplest structure capable of self-replication could have emerged randomly within the available timespan (time since the Big Bang). As of now we have no answer, it seems to be a mathematical impossibility. In other words, you need a miracle for it to happen. Without a miracle it would take billions of times more time than we have available. This was one of the reasons why they had to invent the Multiverse Theory--to sort of "cheat" and create more "available time", so that we can explain the baffling end result, the fact that we have life, anywhere in this Universe.

[@travcollier]

@@vmasing1965 No miracle or even particularly improbable event required (given the spatial and time scales which are huge by human scales). We don't know how abiogenesis on Earth happened, but we've got quite a few likely ways it could have happened. It probably happened quite a few times even, given that our first fossil indications of life date back to pretty much just after the surface of the planet stopped being regularly sterilized by impacts. Anyways, the idea that abiogenesis was some super improbable thing really hasn't been the scientific consensus since probably the 70s. I studied this stuff in the 90s and there were already plenty of greybeards around who were firmly with that consensus view.

[@vmasing1965]

@@travcollier Yeah, the only problem is nobody can explain how it works (within the available volume and timeframe). Calculating back from the end result isn't very helpful, obviously. Yes, we can all see we have life today, yes we can possibly see even gaps with no life and then life again. Doesn't help explaining how did this happen at all. It's only a distraction from the real problem. Assuming the process from prebiotic soup onwards is purely random combinations, this is a purely mathematical problem. As a purely mathematical problem, it has no solutions within the allowed bounds. People who understand math understand this perfectly well. Thus, it could not have been purely random, we're missing something. A missing link, of sorts, if you wish, or a missing mechanism, to be precise. There's been some partial attempts, so we have a little more than nothing in this area of research, but none of these has been able to bridge the gap completely. I don't care about those "consensus"-arguments, either you have a solid working theory or you don't. Most people have the opinion it MUST have worked and COULDNT be anything but purely random process, so "consensus". Experts.... what a joke...

[@travcollier]

@@vmasing1965 The math isn't unfavorable. Autocatalytic chemical networks aren't hard to come by. Making them into a self replicating system pretty much just involves adding something creating an "inside and outside". There is a lot of literature on the topic if you're genuinely interested.

[@hans-joachimbierwirth4727]

@@travcollier If he was interested he wouldn't regurgitate ID talking points. His claims are based on the lies of James Tour.

[@sukruthramesh2147]

The length of the nozzle is determined by the loss in thrust which is allowed. For a conical nozzle, you can imagine that as the length of the nozzle increases, the cosine loses reduces as the flow at exit becomes more axial. This however comes at the cost of heavier nozzles. The solution is then to use a bell nozzle which has high expansion in the beginning and low expansion in the end which makes the exit flow completely axial. The contour is derived using method of characteristics which gives the wall contour angle at every point.

[@danielshapiro7169]

Scott, regarding throttling/shutting-down solid fuel boosters; I'm pretty sure that some boosters can also be 'shut down' with very precise timing despite remaining fuel load. I've read that the Minuteman III (possibly earlier variants) and the Peacekeeper MX missile systems had 'blow-out ports' on their solid fuel stages that could depressurize the combustion fast enough to 'snuff out' the rocket. Between that and the top liquid stage 'doing its thing' were some of the things that improved CEP so much.

[@benjaminshropshire2900]

Personally I've always found it strange that an ICBM would bother with blow-out ports, the "cosine losses" trick should work even better with a suborbital, point to point, "get there ASAP" trajectory. In theory near the end of the flight there should be a direction that you can point the rocket that minimizes the derivative of the arrival location with respect to the accumulated thrust. With a little care in planning the trajectory, that minimum should become zero. In fact, even with blow-out ports, exploiting that would make the delivery less sensitive to variation in how things shut down so you would want to do it anyway so why even bother shutting down at all? My guess is that putting enough compute on the missile to continuously recalculate the rest of the flight was impractical with whatever generation of hardware was in use when it was designed. On the other hand, giving the missile a location/velocity point to hit and computing what that should be with a big computer back on the ground years in advance (and maybe in a bunker a few states over may be much easier.

[@danielshapiro7169]

@@benjaminshropshire2900 Possibly. There might be Time-on-Target constraints they’re trying to capture, or possibly they just want the absolute maximum “throw” capacity out of each stage, with fine-tuned timing on engine cutoff, but without any of the admittedly small losses from the cosine method. You know the expression, “close doesn’t count except for horseshoes, hand grenades, and thermonuclear weapons,” except, when you’re aiming at a super-hardened target like an SS-18 silo or a deep-buried bunker; you need REALLY close. (Though, I do think your idea about guidance limitations DEFINITELY holds water...) Alas, I’m not a missileer, so I cannot even say, “I can neither confirm nor deny.”

[@benjaminshropshire2900]

@@danielshapiro7169 Time-on-target maybe? OTOH parts commonality kind of nixes the maximum performance issue given most of the silos won't just happen to be at extreme range for a standard payload and they won't build a slightly larger payload for things that are closer. Besides, militaries like to over build things. For super accurate: maybe they do both? -- And "I can neither confirm nor deny... because I don't know" is *technically* still correct. :0)

[@danielshapiro7169]

@@benjaminshropshire2900 Yeah, but it’s less cool if you don’t actually know… :-p

[@danielshapiro7169]

@@benjaminshropshire2900 BTW, OTOH? Not familiar w/ that abbreviation. Expand?

[@ryrylandcripps5811]

From what I understand. In a perfect vacuum the most efficient nozzle would need to be infinitely long. Ovesly that would be unfeasible. So I believe they just make it as big as practical and probably balance between thrust to weight ratio.

[@TimothyWhiteheadzm]

Re: fuel transfer pumping. My guess is they will dock then rotate so as to collect the fuel on the outside with centrifugal force. So the pipes must run from the far side, round to the docking ports.

[@Bratfalken]

My thoughts too. Using centrifugal force in some way should help.

[@3gunslingers]

Centrifugal force will not help in any way, because they will not "pump" it. They will use ullage thrusters to settle the fuel to the end of the tank and then they will use the immense pressure difference between the ships to actually transfer the fuel. Starship needs a tank pressure of about 6bar so the Raptors operate optimally. This pressure will be used to push the fuel, while the receiving ship will vent its tanks against the vacuum of space.

[@nevilleoesselke8990]

I rather think they will use milli-g acceleration, with the reaction Control thrusters, because you save a lot of weight with piping and pipes, and also way safer (fewer points to fail) Also it wouldn't really affect the orbit much, because you have so little acceleration. For the operations where starship refuelling is necessary, the orbit is not that important, because you will go to the moon or mars or somewhere else other than earth orbit. Therefore you can "easily" calculate your new trajectory from your new raised orbit.

[@nevilleoesselke8990]

@@3gunslingers Venting will not work, just keep accelerating, because both ships should have the same pressure, so the liquid and gases can transfer. Also you still need pressure in the tanker starship for it to return to earth, otherwise you destroy the whole purpose of starship with reusability.

[@3gunslingers]

@@nevilleoesselke8990 You can always boil off some of your remaining fuel to get your tanks up to pressure again. That's no problem. But what do you mean both ships need the same internal tank pressure to transfer fuel? Why not lower the pressure in the receiving tank to help with the transfer?

[@gen0megen0me93]

Well designed nozzle will have very "linear" flow, nothing turbulent. Pressure inside will drop in very mild manner possibly with spherical or even flater isobars looking from throat. Any idea what could be a range of gas speeds and temperatures from max throtled to full trust in engine?

[@williamgreene4834]

Rocket exhaust velocity is much slower than orbital velocity so as you get close to orbital speed the exhaust is actually following you. :)

[@klausmuller7488]

Concerning the life in the Universe question, the Abiogenesis Series from Dr. James Tour (the Nano Cars Guy) is very enlightening.

[@jimsvideos7201]

You can shut a solid rocket motor off by venting pressure, but I have no idea how much finesse you have doing that.

[@joshforsythe4555]

By adjusting the size of the hole you are using to vent the gasses inside you could theoretically get an arbitrary throttle level between max thrust with no hole and the lowest pressures that sustain combustion with a massive hole. The biggest issues with this though are that performance takes a massive hit, and you have to figure out what to do with all these hot gasses you are venting (ie how to vent them without melting something and without generating any thrust)

[@williamgreene4834]

You can neutralize the thrust but you can't shut it off. Also srb exhaust is so hot it would boil stainless steel into steel steam. Solids are just on. :)

[@PinataOblongata]

You could just detach the SRB while it's still burning, so it goes flying off and stops imparting thrust to the main vehicle. Probably not very safe, but possible :D

[@jamesrosar3823]

Remember that Virgin Galactic uses a solid rubber mixture fuel and nitrous oxide for the oxidizer in their craft. The fuel burns well enough at full flow of the oxidizer, but mostly snuffs out when the the nitrous is shut off.

[@williamgreene4834]

@@jamesrosar3823 Virgin uses a hybrid motor which can be throttled and shut off. Solid rocket motors not so much. :)

[@timprice7627]

“It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you may meet from time to time are merely the products of a deranged imagination.” - Douglas Adams

[@francispitts9440]

I have to look up things when I listen to some of your videos but it’s always interesting especially when I learn something new. I appreciate the amount of work you do for these videos.

[@gustavodziura670]

I did a quick search on the olympus mons air pressure and it seems to be about 30 pascals, and that is a LOT more than the atmospheric pressure at 200 km in Earth (0.000047 pascals)

[@mrpicky1868]

14:23 answer is yes. big difference in performance, And cost and predictability in storage and in use

[@QuasiRandomViewer]

10:21 (Re Antares solid upper stage.) Clearly they can design a trajectory to match loading and predicted performance ... _if_ that upper stage performance is well characterized. I'd love to know if their closed-loop guidance takes observed engine performance into account sufficiently to predict any variation in tail-off and shutdown characteristics. I assume not, and that they have simply characterized the Castor 30XL sufficiently that they are able to hit the range of acceptable insertion parameters. (Solid rocket motor thrust termination devices exist, but I don't believe the Castor 30XL uses them.)

[@ImieNazwiskoOK]

In terms of capability of New Glenn kinda weird thing about it is that we really don't know much. It is huge and has payload of 45 tons to LEO but there are still many questions. Like 45 reuse or expandable or payload to higher orbits.

[@the18thdoctor3]

45 tons when reusable, there probably won’t be an expendable version.

[@simongeard4824]

They also don't have much idea about their upper stage either, since while the current design features an non-reusable upper, they've also got their Jarvis side project exploring the idea of a reusable one. This presumably reflects the idea that simply building a bigger Falcon 9 isn't going to be competitive in a world where Starship is even bigger still *and* fully reusable.

[@ImieNazwiskoOK]

@@the18thdoctor3 Source?

[@longlakeshore]

In proportion to width axial nozzle length is shorter for engines used in the atmosphere and longer for those used in the vacuum of space. One of the reasons the nozzle of the Apollo Command and Service Module (CSM) was so huge is that it was only used in space. Air pressure limits how long the nozzle can be especially in the lower atmosphere. Some upper stage nozzles these days are extendable to take advantage of this while keeping the overall length of the stage as compact as possible to shorten interstage distance in the rocket stack or fit inside the nose cone. The longer the exhaust is kept in a nozzle the greater the thrust an engine can produce. There are other factors at play like at what percentage of thrust the engine will be used and the rate at which fuel can be oxidized in the combustion chamber. There are always engineering design trade-offs.

[@AubriGryphon]

My feeling on life is that it emerged on Earth almost as soon as conditions were such that it could exist, therefore it's likely to arise quickly anywhere that is reasonably friendly. That said, life began 3.7 billion years ago, and then it took another 2.5 billion years to work out multicellular structures. The first things we could properly call animals are only half a billion years old. So most likely, the universe is full of bacterial "slime worlds" with only a few hosting macroscopic life and intelligent life being very rare.

[@PongoXBongo]

For the Starship refueling, could they use the same plumbing as used with the launch pad umbilical arm?

[@brandonberchtold9484]

7:14 There is actually an optimal shape for a nozzle contour and it's calculated using the method of characteristics which was one of the earlier CFD methods before the finite difference and finite volume methods became more mainstream. You are right though with the concept of expansion waves cancelling out with compression waves. Viscous effects in the wall boundary layer complicate things though so it generally does boil down to guessing with CFD and checking with a physical prototype.

[@joshuakeunecke5431]

6:19 The two Starships could also dock and then start to rotate around each other. I imagine the centrifugal forces would push the propellant to one side of the tank, from which you could then drain it. That way you would not have to expend any fuel and your orbit would stay the same too.

[@excitedbox5705]

My question is: Why not make a tank inside a tank? Assuming both fuel and oxidizer are roughly the same pressure and temperature in their liquid state, you would only need to insulate the outer tank to keep both fuel and oxidizer cryogenic AND the pressure difference between the inner and outer tank would be less than going straight to atmospheric pressure, so the inner tank could be really thin (more just to keep fuel and oxidizer separated). Since volume increases faster than surface area, you would need to insulate less surface and less material for the structure. You could also eliminate the feeder pipe going from the top tank to the engines. This means no external plumbing needed. A stronger shape overall. Depending on the design, both liquids could be fed from either end. The inner tank could be a bladder, attached to the bulkheads at either end of the outer tank. This would leave you with a smooth aerodynamic shape that is easier to manufacture. Which brings me to my other question: Why not roll the tank from one long tube of steel? A 32cm OD tube with 64mm wall thickness can be rolled to 10 meters with a 2mm wall thickness. Seems like using a continuous casting and stretching it over a mandrel to roughly 60cm like they do with pipelines and then using a rolling mill could get you a "finished" tank in about 1 day.

[@Qkriek]

After seeing a bunch of depressing things on the internet, your video is a breath of fresh air. Thanks Scott!

[@dawfydd]

Hey man random Scifi based question which is a little more than "Whats your favorite scifi one man craft" but given tomorrow you could own preferably for pleasure (and not to transport goods/people/take part in military exercises etc) Which of the space capable one man spaceships you've seen all through Scifi would you most like to fly- and keep as a flying experience to repeat. The assumption is you can also get into space easily to joy ride these fighters so you don't need to restrict craft like the first couple of Starfuries from babylon 5 earth alliance who can't enter atmosphere.

[@smipi1]

Hi Scott, The axial distance between the throat and maximum diameter of the nozzle is a side effect of optimizing the nozzle shape to avoid termination shocks from forming within the nozzle. A termination shock is characterized by a sudden increase in temperature and pressure, as well as a drop to subsonic flow. The whole aim of the divergent end of nozzle is to accelerate the flow in the supersonic regime to get the pressure close to atmospheric for maximum thrust. A boundary shock would ruin that because a divergent nozzle would decelerate the resulting subsonic flow. No need to elaborate on how undesirable a sudden increase in temperature and pressure within the nozzle would be. 😉

[@Papershields001]

Man terraforming is the MOST human thing I can imagine. We see Mars, an entire world of pristine untouched wilderness and the first thing we think to do is destroy it in order to make it more useful to us.

[@andersjjensen]

Que the thing Scott said about life evolving to fill every niche it comes across... But honestly Mars sucks. If we could spin up Venus that would be a much better alternative...

[@CheMechanical]

RE the hazardous nature of fuels, there are at least two ways to look at this concern: (1) the nature of the individual components in terms of their potential impacts as they are being stored and handled for use (think flammability, toxicity, reactivity), and; (2) from a broader life-cycle perspective. Life-cycle (or lifecycle) includes the impacts of the fuel components in terms of risks to create/obtain the ingredients, modify them AND the impacts of the combustion products generated during intended use on the environment. At least one common component is also a greenhouse gas (methane).

[@scroopynoopers2892]

very happy for Astra :)

[@mikeebee8501]

For nozzle design see “ Design of a Supersonic Nozzle using Method of Characteristics IJERT”. Back 50 years ago my Gas Dynamics professor said that to account for the boundary layer in the nozzle you needed to design them with a 2% or 3% larger area ratio.

[@matiaedo9634]

hey scott, will you ever come come back to ksp? we miss you!

[@mrdeuce]

Yes

[@PrinceAlhorian]

Yes please, Jeb's getting out of hand.

[@helicocktor]

Probably waiting for KSP 2

[@EaglePicking]

@@helicocktor Yeah, same here.

[@bradisley517]

First the design is built around the heat it can take and the optimum expansion of exhaust gas to outside pressure. The problem is optimized for each stage for sea level to space. The actual formula for specific impulse that takes this into account is about 3" long. The engine can not break the speed of sound internally so the higher the heat the faster the exhaust can go.

[@RevMikeBlack]

I thought the main issue with landing two Falcon Heavy boosters simultaneously was the shockwaves generated by the two objects as they are hurtling toward the ground. If the landings are completely symmetrical, the shockwave from one could destabilize the other. This doesn't happen if they're staggered slightly.

[@found6393]

The problem with determining how common life is in the universe is that our current sample size of life-bearing planets is 1.

[@LabRatJason]

I think nose to nose transfer makes the most sense for Starship, because the outlet of the tanks is at the aft side, so if they go nose to nose, then spin them to create a tiny bit of gravity, it will keep the liquid pressed into the exit of the tanks... as the fuel and oxidizer transfers, the center of rotation will shift from one vehicle to the other. That will be an interesting dynamic to control for.

[@seanbaskett5506]

Anytime I see starships docking in orbit, I always think of the opening scene from Dr. Strangelove where the bombers are mating to the tune of "Try a Little Tenderness". It's amazing how many innuendos come from aerospace engineering.

[@alan2here]

"Hey Grek, the small blue planet, yeah the nearby cold one with all the ice and nothing to breath, well some H2O based chemistry there seems alive, they'll be incredibly soft and fragile and communicate by making the atmosphere shake." "Don't be stupid zmukkruk, nothing can survive on that frozen block of inactivity, be reasonable, now my best bet on the god suns atmospheric layer, … no hear me out, it's thin but theres a lot of it, and you never know".

[@NarwahlGaming]

"Grek! This planet holds one of the most dangerous creatures in the known universe!" Human: "This is my kitty, Mr. Nibbles."

[@alan2here]

"Smukkruk, look, the atmosphere is practically made of flammable, explosive, toxic, corrosive, rot and decay inducing Oxygen! There's nothing more electronegative except fluorine! Face it, any life there would just explode. Like … Hello, nice to meet you, kaboom, the end. Nothing could survive in an oxygen atmosphere."

[@jwstolk]

SpaceX added radar-reflective paint to the concrete landing pads, for better height measurement. Obviously this was not an issue on the steel decks of the drone ships.

[@DominikJaniec]

interesting idea with handling Δv of solid rocket boosters! didn't know that, thank you :)

[@UncleKennysPlace]

I wouldn't be surprised if the landing barges had localized GPS correction.

[@maesterwillyofthehouseofboink]

Just discovered this place, but it's allready in the top 3 of my favorite sci-fi channels for 2021 and beyond... 🤓 🥳

[@jeremiefaucher-goulet3365]

The best évidence we have thus far that life might be common in the universe, is when we consider how quickly it appeared on Earth after it's formation. But then again, it was very simple monocellular life for billions of years.

[@markhuebner7580]

Awesome Scott! Thanks! Lots of great details on lots of interesting rocket & space things, beautiful!

[@randomstuff2.076]

CAN we get Scott to voice act for a space simulator as ground control 😂, this is the voice I want to hear when something goes wrong 😂

[@sawyerw5715]

For refueling, it seems like it can be mostly handled by pressure control. You pressurize the source tank higher than the sink tank and the fuel should flow that direction (providing there is an outlet connecting the tanks). Adding some appropriate valves I think then you don't need to have artificial gravity from thrust to move the fluid.

[@TheEvilmooseofdoom]

You need some gravity otherwise your gas just forms bubbles.

[@brunnorpdias]

Engine axial distance question is really interesting, gonna look it up

[@uuzd4s]

If however many Question's themselves were briefed over before the monolog, I'd likely hear of a few I'd stick around for. Always a fan !

[@Kaget0ra]

The US Navy holds patents for a number of planet destroying weapons so there might be some legal challenges depending on how you go.

[@jpdemer5]

Just pay the royalties, and you're good to go.

[@johndododoe1411]

Weapons patents have never limited the actions in a shooting war.

[@spacexrocks1041]

A lot of patents are crap to impress investors. I used to write them. Just because a patent claims they can do something, it doesn't mean they can.

[@jpdemer5]

@@spacexrocks1041 We used to joke about military patents: Is the Pentagon planning to to sue the Russians for infringement? Do they have to have patent coverage where the missiles explode? So many absurdities...

[@jaydonbooth4042]

I'm all for setting up large areas of Mars as wilderness preserves of sorts, get it done and figured out now long before humans come in to start colonizing. We have the chance to do it how it should've been done on Earth, sure even if there isn't life on Mars just protecting certain areas in their natural state so that even a couple thousand years from now you can still visit Olympus Mons, Valles Marineris, Elysium Mons, etc and enjoy them as they were before humans came and developed large parts of Mars would be a good thing to set up beforehand. And set them up as a proper wilderness preserve, not just like big tourist parks. If we set it up as solidly as possible now hopefully future people would choose to continue with preserving those regions. Would've been nice if we had done the same with, for example, the New World, before settlers came in to tear the place up and set down roots in a way that now makes it incredibly hard to designate new areas as preserves to keep them from being further destroyed.

[@johndododoe1411]

Don't forget the predictable exceptions when any strategic resource is found in a preserve area. Plan accordingly.

[@uunter]

Hey Scott, I’m flying a Cessna down from the Bay Area to catch DART. Maybe I’ll see you down there. I imagine you don’t want to change plans to fly with a stranger, but if that sounds like fun, I have a couple open seats.

[@scottmanley]

I've got the whole family with me, and I've got some special access organized, but I might see you in Lompoc.

[@cuachristine]

@@scottmanley Hey guys, what is the best spot to see the launch? We are heading there as well.

[@spacexrocks1041]

Hoping to see it here in San Diego, like the InSight launch. SoCal is full of idiots and stoners that every night launch generates lots of UFO stories.

[@uunter]

@@scottmanley Same offer for NROL-87! DART was awesome; can't wait to see a booster landing, weather permitting!

[@zeg2651]

Damn Scott these are too many wonderful videos in one week 😍

[@kneekoo]

0:22 Astra went from rocket strafing to orbit in less than 3 months. Quite a feat of engineering! :D

[@Cg23sailor]

Just watched Falcon 9 launch the DART mission. What was going on with the nozzle on the second stage MVac during the second burn? It was like a very defined section of the bell was heating differently than the rest. Or like the camera was both over exposed and under exposed at the same time for different sections.

[@chrisglen-smith7662]

@Scott Manley. Propellant transfer in orbit. Could they do the propellant transfer passively by creating a temperature difference? i.e. chill the receiving tanks, and warm the source tanks then the vapour pressure does the work for you and it won't matter if it's gas or liquid as it moves. Might be more difficult to monitor the quantity transferred but that should be solvable.

[@absalomdraconis]

The bigger the desired pressure difference, the bigger the required temperature difference. Pumps will likely be faster _and_ easier.

[@chrisglen-smith7662]

@@absalomdraconis so? Bigger the flow rate the bigger (and heavier) the pumps.

[@chrisglen-smith7662]

@@absalomdraconis @Jared Maddox Any pressure difference will work, it would be a compromise with speed of transfer. Benefit is you save the weight of pumps and you don't need to settle the propellants. It may even be possible to use orientation to the sun to achieve the temperature difference.

[@chrisglen-smith7662]

@@absalomdraconis someone probably smarter than you or I would have to do the math.

[@dsdy1205]

17:54 For anyone interested, Cool Worlds has a really interesting "series" of videos on this where they tackle the statistics of ET life and answer "how unusual is X" where X has been many variables concerning the occurrence of life.

[@caldodge]

How about butt-to-butt, then a slow rotation around the long axis? That would push propellant to the outside of the tanks. Put pickup pipes inside the tanks against the walls. Pump vapor into the center.

[@airplanenut6242]

The true secret to rocket nozzles is that you use whatever RPA spits out and justify it later. 😁👍

[@jworldwide904]

I've got a question... Why is DART launching from Vandenberg? I read that the 2nd stage is going to do a dogleg maneuver to the east shortly after it ignites. This, combined with the initial SSE trajectory of the 1st stage seems to suggest it would be easier to launch from Kennedy. What am I missing?

[@Neyck97]

Major concerns about nozzle reside into the maximum amount of energy recovered from gas expansion, which is directly linked to how little entropy is generated by expansion / compression shocks : the lesser entropy, the better ! But at the same time, you want the expansion to be as quick as possible so you can limit the nozzle size, or thermal stresses… And that’s without even mentioning manufacturing costs ! Since we cannot derive a perfect nozzle shape from three dimensionnal supersonic flow equation yet, if there is one anyways, most nozzle are engineered by trial and error, hence the number of designs and applications !

[@Squossifrage]

18:33 Would you say that life, uhh, finds a way?

[@sandrob.2307]

Hi Scott Thanks a lot for all the time you spend to answer all the questions. As an eclipse chaser myself, i was wondering if there are any reports of astronauts seeing the solar corona from space? With no Earth atmosphere i would guess it should be fairly easy to block out the sun's surface with let's say your thumb? Many thanks in advance! Cheers, Sandro

[@solidus4prez]

6:26 I saw the "butt to butt" question and wondered if my "cloud to butt plus" plugin for chrome hit it but then realized it's in the video

[@HalNordmann]

Great video Scott, nice to see you talking about something that isn't SpaceX related for a change! A question: What sense does it make to have a liquid-fuel lower stage and solid-fuel upper one? Is it because of engine ignition issues or what?

[@hamjudo]

A working solid fuel upper stage with suitable specifications was available to them when they were designing the rest of the rocket. An upper stage has to be able to handle all of the vibrations of launch and start when asked. It also needs to remain fueled through all of the expected launch delays. Liquid fueled upper stages need a connection to the tower for fueling and draining. Solid fueled rockets are always ready to go. They are fueled when built. They may cost much less to buy. Reliable working liquid fueled rockets are usually better in almost every other way to ones with solid fuel, if you can put the fueling arm onto the launch tower. The BE-4 is an example of a liquid fueled rocket engine that does not work. The rest of the specifications don't matter if an engine doesn't work.

[@frankgulla2335]

Wonderful answers to some great questions. I might point out that NO ONE is qualified to answer the question "how common is life". Thank again.

[@wskinnyodden]

Dang, and a polar orbit no less! Ain't those harder to achieve comparing to an equatorial orbit? (Geostationary would be better but not a bad start at all!)

[@techondrugs8388]

17:55 to 19:28 is a great clip to start a alien apocalypse movie.

[@SteveBakerIsHere]

That kind of short-range - directed radar - used just for ranging - is what Tesla delivered in their cars (until very recently), and other car makers are still using in huge numbers...if a dozen Tesla's on a freeway don't interfere with each other - then it's certainly within bounds of reason to expect that two Falcon-heavy cores could both use similar technology for accurate ground ranging without problems.

[@menotyou1234]

What spacing would be required between Starships to prevent a chain reaction domino effect if one ship blows up in space..???

[@lepompier132]

Scott, to transfer fuel from one Starship to the other, they could use the same tech to transfer propane in liquid form. Thay use pumps, so the same can be true for methane and Oxygen in liquid form.

[@jdice73]

Is there a way to come to a complete stop in space? For instance, when docking the space station, you often come to a stop but relative to the space station. What does it me to come to a complete stop in space. Is it possible? How could it be measured?

[@WarrenLacefield]

That's a curious question. What does a "complete stop" mean? The earth is moving, the solar system is moving, the galaxy is moving, etc. Is there some universal "center point"? However, internal motion does appear to stop near absolute zero temperate. But that is almost "by definition". Perhaps the closest thing would be a form of stasis, in time perhaps, also almost by definition. Would such a "stop" be at zero entropy? Wouldn't that be "total information" - apparently forbidden by the uncertainly principle?

[@fluffly3606]

I can imagine an episode of a sci-fi anthology series where some madman tries to de-orbit the moon using thrusters placed close to densely inhabited areas and the protagonist has to make the hard decision to nuke those in order to hopefully save the Earth, maybe with an ending scene emphasizing the uncertainty of how the acceleration the villain accomplished will eventually affect the wider solar system. Tens of millions were sacrificed to save billions, but will that last?

[@Blandge]

Holy crap, he answered my question. Thanks, Scott.

[@victorillo377]

12:04 HAHAHAHAHAHAHAHA I see an IbxToycat fan ❤

[@jaroslavstava3704]

ibx2cat ftw

[@wodddj]

toycat + manley = matt lowne

[@railgap]

Is no one using phase separation materials any more? If so, they wouldn't need to have thrust to keep gas out of the lines. The tech was well understood and in use in the 80s when I was at Martin-Marietta Astronautics (south of Denver). However, I honestly don't remember whether it can be used on cryogenics.

[@jamesrussell7760]

How do you design the optimum nozzle shape? Well, you could say the hell with it and go for the brute force approach, AKA the SRB's that powered the shuttle.

[@JoeL-hr6uo]

Just curious with fueling transfer, could the action of the pumps pushing fuel to the receiving ship be enough thrust to keep the fuel to the bottom of the supply ship??? Or maybe use the boil off of ch4 and o2 to freed small thrusters??

[@mocko69]

12:10 yayyyy free shoutouts!

[@rauckr09]

I really like your channel. You are extremely knowledgeable!!

[@JCUDOS]

20:57 "It's going to be a horrible movie" Hahaha

[@HotelPapa100]

Considering it took life less than a billion years to develop on earth I'd say it's pretty inevitable given that conditions are right. Chemistry that can replicate itself has a pretty big darwinian fitness advantage over other forms of matter.

[@EscapeMCP]

10:00 "Blue origin may have partnerships that may result in them getting payloads that the other ones don't want to look at". Are you on about Soichi Noguchi having Prime???

[@calebgangte1228]

"It doesn't use thanks, it doesn't use wishes and prayers" wheeze🤣🤣