Will Starship Fall Over?

Подписаться 11 тыс.

Просмотров 6 тыс.

50% 1

Starship is a tall and thin vehicle that looks much different than the Apollo Lunar Module. What is the chance it will tip over when landing on the lunar surface?
@Eager_Space on Twitter
Triabolical_ on Reddit
/ eagernetwork
/ eager-space-1038430522...

Опубликовано:

8 сен 2024

Ссылка:

Скачать:

Готовим ссылку...

Добавить в:

Мой плейлист

Посмотреть позже

Комментарии : 83

@Zeppflyer Год назад

Doctor K’s Engine Elixer: A more legitimate company than Established Titles!

@king_br0k Год назад

Now Teller's Tachyon Tablets on the other hand is definitely one of those scam products, glad they are no longer sponsoring Eager

@solarissv777 18 дней назад

It literally states "лохотрон" (lohotron) on the bottle that is basically russian slang for "scam" 😂

@carlgeorgbiermann2915 3 месяца назад

Experienced KSP player here. Things that come to my mind (not sure hiw well they translate to the real world): 1. The landing legs help most if one leg directly points downhill. If the downhill direction is at 45° between two legs, the width of the base is significantly smaller. 2. Bouncyness: Landing legs are designed to take the impact of landing, which means they need some room to flex. During landing, *especially on slopes*, the lander will swing a bit back and forth before settling to its stable position. If during this motion, the COG is outside the ground area, it will tip over. 3. Torque: When the lander leans over, the downhill facing leg(s) need to bear a higher load. This causes them to give in more, amplifying the tipping. This problem is especially bad for tall landers. That's why this starship render really scares me ...

@listener-tt1gw 2 месяца назад

Nice tips for a noob ksp player.Mun was so punishing before!

@donjones4719 Месяц назад

Another factor has occurred to me, one no other lander has, real or fictional. Starship will be coming down using multiple auxiliary engines near the top of the ship. Any tipping could be compensated for by differential thrust to help the legs settle and use the self-leveling feature we're promised they'll have.. Also, if the angle is too bad the ship can lift off and settle a few meters away - although that will depend on whether it can carry enough propellant reserve to do that. Even at its most basic, I expect the engines to decrease their thrust gradually after ground contact is made. If the angle is bad the computer can simply "abort to orbit." The aux engines go to full thrust and the Raptors ignite. The two used for most of the descent can be kept ready to ignite - I imagine.

@Ormusn2o Месяц назад

@@donjones4719 This is not 60s anymore where the pilot is eyeballing the landing site. The landing place will be precisely picked and Starship will land with accuracy below one meter. There is likely to be about 2-3 degrees of slope on the landing site. Everything else is just being cautious. It might not be for Artemis 3, but unmanned construction machines are likely to flatten the landing zone for other missions, and then we will get a concrete landing pad or catch tower.

@donjones4719 Месяц назад

@@Ormusn2o True, I expect Starship to have a well chosen site that it accurately land on. I list all of its capabilities here to address the often repeated concerns and to get people to *shut the fuck up about it.* :)

@Ormusn2o Месяц назад

@@donjones4719 Yeah, I think one of the renders of starship did not even had retractable legs like that, they were more low profile, because SpaceX knows you don't actually need that wide of a bottom. Good for you fighting the good fight in the comments too :)

@danmosenzon1477 Год назад

Seems pretty conclusive, other than the fact that the model does not account for margins in the propellant, or the leftover propellant in the header tanks. This is probably a good approximation.

@user-sn8oe5sb1b Год назад

Will HLS even have header tanks? I don't see a reason for them.

@junkdriver42 Год назад

This and launchpad astronomy are becoming my favorite space-related content channels.

@EagerSpace Год назад

Thanks. I aim to please.

@lazarus2691 Год назад

2250m/s is pretty tight for getting to NRHO. Starship might just manage it thanks to it's high TWR, but I'd imagine SpaceX will still include some extra margin on that, which will add a significant amount of weight thanks to the rocket equation. NASA budgets for ~2750m/s, depending on the exact profile.

@EagerSpace Год назад

Definitely; I went with the minimum because that would give the lowest propellant mass and therefore was the most conservative choice for this analysis. Margin would definitely be a great idea. If you have a link for the NASA budget I'd love to read it.

@lazarus2691 Год назад

@@EagerSpace There's not much to read unfortunately, AFAIK they haven't justified their reasoning for any of their estimates. 2750m/s appears to be the most commonly used figure. for example page 18 here: www.nasa.gov/sites/default/files/atoms/files/20191030-nac-heoc-smith-v3.pdf and page 8 here: www.nasa.gov/sites/default/files/atoms/files/20181207-crusan-gateway-reduced-v4tagged.pdf They used 2700m/s in a CLPS presentation and I think I even recall 2850m/s being thrown around back when Gateway was still DSG. If I had to guess, I'd say that first braking into LLO and then landing as depicted in one of the graphics is less efficient than landing directly, and also that an inclination change will be needed after a stay on the surface unless the landing site is exactly at the pole. And of course, they probably weren't expecting whatever lander they ended up with to be quite overpowered as Starship, which can easily manage a TWR well into the double digits, as opposed to the measly 2 that the Apollo ascent module had.

@GlutenEruption Месяц назад

If the recent landing fails have taught us anything it's that dynamic stability is MUCH more important than static stability. Remember, in 1/6g, the force it takes to lift that cg past the tipping point is 1/6th as much but the lander had the same momentum as on earth, severely reducing stability. Three major issues you didn't account for are horizontal velocity and landing at any angle where one or two legs touchdown first and the massive torque that will exert on the lander, and stability ie how far upwards the CG has to move before reaching the tipping point. The dynamic movements of approach and landing on a very uneven, soft, grabby, and non-uniform surface in 1/6g is extremely unforgiving and even a minuscule horizontal velocity or a forward leg snagging is all it takes to topple a tall lander.

@philippeferreiradesousa4524 Месяц назад

The landing engines are a ring of hot gas thrusters higher than the center of gravity, so there is no problem cancelling the tipping torque.

@GlutenEruption Месяц назад

Not true, that's the pendulum rocket fallacy in action. Because they're part of the rocket, it doesn't matter where they are, it doesn't change stability at all.

@philippeferreiradesousa4524 Месяц назад

@@GlutenEruption It does. We are talking about after the landing happened, not in flight. You can: - cancel the remaining torque by applying an opposite torque around the center of gravity - put the CG within the convex hull of the legs if needed by applying torque around the center of gravity To do that with engines at the bottom you need to take off again. With engines at the top you are good.

@WilliamDye-willdye Год назад

Hey there, YT algo! Notice this comment. Use your powers of automatic sentiment analysis to see that I am happy. Now start sending over more subscribers to technical deep-dive space channels such as Everyday Astronaut, CSI Starbase, Terran Space Academy, BPS Space, and others. This channel deserves a wider audience.

@concretedonkey4726 Год назад

that bothered me from the first time I saw it... but I guess I have too many KSP memories... I will never forget the mission to save the mission which was supposed to save a tipped over lander but ended up tipping over...

@awsumguy-bh9pz Год назад

severely underrated channel

@therichieboy Год назад

I think starship's hull is nearer 4mm thick but that may change by the time they're ready to land it in the moon. It will also have landing engines higher up the hull and very possibly 9 raptor engines in the skirt.

@simonschaller857 2 месяца назад

I can imagin them putting 30 meter long falcon 9 style legs on the lunar starship

@donjones4719 Год назад

Thank you for working this out and *demonstrating* the answer. There are too many assertions one way and another on various forums. Btw, do you have a brother who does Greg's Airplanes and Automobiles? Your voices and cadences are very similar.

@EagerSpace Год назад

Nope, though I think you're not the first person to notice that.

@Ormusn2o Месяц назад

At angle like that, it seems like almost any lander would just start sliding down a slope anyway, until it leveled out more.

@gus2747 Год назад

Fuel slosh would reduce the angle - so would lateral velocity at touchdown - so would landing on uneven ground. Simplified 'back of the envelop; calculatins are useful only if you have a huge margin. If a simple static-force calculation says you can handle 20%, you can in fact handle 10%. So current Starship will be too unstable for exploration. HOWEVER Artemis is not exploration. If the first mission to Shackelton crater has wide, heavy DISPOSABLE landing gear and the crew mark out level ground and subsequant Starships land on the level ground, a less stable design is OK.

@dsdy1205 Год назад

It would be interesting to take this stability model and deduce how much lateral velocity Starship could tolerate at touchdown on a level plane. I know, with computers this is realistically as close to zero as makes no difference, but still.

@EagerSpace Год назад

I considered doing that, but I was too lazy to do it. It would be fairly straightforward.

@sophrapsune Год назад

How on Earth in Starship supposed to keep its fuels at cryogenic temperatures for the weeks it would take to complete a lunar mission? How much fuel can Starship expect to have off-gassed by the time it needs to launch into lunar orbit? Are they expecting to take an alternative energy source to keep these fuels refrigerated over those weeks? Or are their tanks just absurdly well insulated in vacuum flasks to keep LOX cold for weeks in direct sun, with all the weight that implies?

@EagerSpace Год назад

An engineering analysis could be done to quantify this, but I haven't do it, so here are my thoughts. The only heat gain on the moon or in orbit is from solar radiation. Lunar starship is white to reflect as much of the energy as possible, but some will heat up the structure. When you put heat into cryogenic liquids, they don't heat up but rather some of the liquid turns into gas. That absorbs a lot of heat so that the rest of the liquid stays liquid. So the real question is how much of the propellants they will have left. My understanding is that it won't be significant in this sort of scenario, but I haven't done any analysis. I do know that NASA has done some work to develop techniques to keep liquid hydrogen liquid for long flights, and that's much harder to do than methane or oxygen as the hydrogen temperatures are so much colder.

@zeevtarantov Год назад

@@EagerSpace Can they spend some electricity to cool the propellants? How much solar panels or batteries will that take?

@fascistpedant758 Год назад

How much more chicken broth would it take if the legs sink 2 meters into the soil on one side?

@cryptopolice6202 Год назад

If you would carefully place it like that with a crane, that is. Landing it on that angle would not work out so great.

@nikolatasev4948 Год назад

Interesting calculations. There are a few more factors that could significantly contribute. First, the terrain tilt may not be towards one leg, but between two legs. The deviation would then be closer to the half-side of the landing legs square, as opposed to half the diagonal. This significantly reduces the stability. Second, the terrain may depress under one or more of the landing legs. It doesn't need to be much to throw the thing off-balance - considering that landing on tilted ground puts a lot more weight on the lower legs than on the upper ones, and Starship weights quite a lot. Third, horizontal speed massively changes the max tilt angle. Starship would be particularly vulnerable to sideway speed, since its high mass would have high inertia. If the sideways speed is towards the lower end, the pressure on the lower legs would make them even more likely to sink in. I don't think this factor would be much of a deal, since computers would be in control, unlike in Apollo, and they would likely negate the horizontal speed. In all, Starship would be crazy efficient if there is a landing pad prepared. But the first landing would likely have much larger legs and probably ballast in the lower parts, and the rovers it carries can prepare landing pads for the next landers. I'm sure SpaceX would do their homework so the lander does not fall over.

@TheEvilmooseofdoom Год назад

Doesn't matter if it tilts towards one leg or two, it's the net that counts. They already know the terrain doesn't compress very easily but it's of course not impossible. They'll kill the horizontal speed much the way Apollo did and likely try to come in as straight up and down as possible, they won't be landing under manual control. Lastly landing legs can be made to compensate for a lot including self leveling.

@snower13 Год назад

Compressibility (or maybe there are more appropriate terms) of the regolith is another factor I would guess.

@akwakatsaka1826 Год назад

Thank you for this

@lostcarpark Год назад

In the equation at 6:55, I see 9.8. I'm assuming that's for gravitational acceleration. If so, I think you might be using the figure for the wrong planet. If so, I think the fuel needed to reach orbit could be quite a bit lighter. I mean, you'd probably want some extra fuel for contingency. If I'm wrong, please let me know. If that's correct, it would be interesting to see how it affects the equations.

@debott4538 7 месяцев назад

Apparently, 9.8 (or 'standard gravity') is the correct value here, because Isp is a weird bastard child of the metric and imperial systems. The value that actually matters in the rocket equation is the exhaust velocity v(e) of your reaction engine, and v(e) = Isp * 9.8 en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

@ThatBoomerDude56 Год назад

Not quite complete. But the rest of the calculation is more complex. *It could tip over if it:* (1) Contacts the surface a particular lean angle X ; (2) AND if it contacts the surface with horizontal velocity above Y. Yes, it's likely supposed to descend completely vertically. But the above is relevant in case it does not.

@EagerSpace Год назад

Definitely true. For #1, I included the Apollo 15 example which looks really tilted to me and yet Starship would be fine with that angle. Starship is probably a bit more immune to this because the landing pads are so much farther apart, but it's still possible. For #2, I'm expecting that starship is probably going to autoland and that keeping the horizontal velocity low will not be a problem. Apollo was all under 1 m/s horizontal velocity and that was with hand control. Could still happen.

@ryanmcgowan3061 Год назад

Worse case scenario: It contacts the surface at +X° and with Ym/s, then tips to the opposite -X° in rebound, then suddenly halts Y to 0m/s as a leg digs in, with +X being naturally inclined away from Y direction to halt the horizontal translation. Fuel slosh is not just the off-center weight, but horizontal momentum still traveling at Ym/s that must decelerate to 0 with an initial state already in the worst sloshed state, which is also not perpendicular to gravity, but swinging up the side. Also geometry of the legs should assume they are at 45° (if 4 legs), not 90° to the slope direction, reducing the horizontal component of the leg to about 71%, and mounted further from the apex of the rocket body's radius as you rotate to 45°. On 9m body with legs extending out 8m from center, the mounting point of the leg at 45° is only 3.18m from the center of the body and the foot is only 5.66m from the center, barely over a meter wider than the body itself.

@1lustigermenschfighterlp458 6 месяцев назад

Very relevant (:

@alkimball8920 Месяц назад

Beer and hotdogs? Lol.

@alkimball8920 Месяц назад

I worry about the modulus of elasticity of lunar soil (Young's Modulus here on Earth) and how much can it vary before contributing to the final angle of 'tippyness' of the rocket. How do you predetermine what you're up against without preparing the landing spot?

@EagerSpace Месяц назад

It's definitely a concern, but I think there is some decent data from Apollo that will probably help out. Before Apollo there was a lot of concern that the landing pads would sink into the soil but it turns out that there was not issue at all. Starship is a different scale, of course.

@donjones4719 Месяц назад

@@EagerSpace Good to see you're still replying here. Something occurred to me today when replying to someone else here. Another factor has occurred to me, one no other lander has, real or fictional. Starship will be coming down using multiple auxiliary engines near the top of the ship. Any tipping could be compensated for by differential thrust to help the legs shift and settle and use the self-leveling feature we're promised they'll have. (Very deep "throttling" can be accomplished by shutting down an engine in each set.) Also, if the angle is too bad the ship can lift off and settle a few meters away - although that will depend on whether it can carry enough propellant reserve to do that. Even at its most basic, I expect the engines to decrease their thrust gradually after ground contact is made. If the angle is bad enough the computer can simply "abort to orbit." The aux engines go to full thrust and the Raptors ignite. The two used for most of the descent can be kept ready to ignite - I imagine.

@gorgonbert Год назад

How much horizontal velocity component at time of landing would be acceptable? (Assuming that the target point is not 100% certain at time of approach and needs some adjustment just before touchdown. Unlike Falcon, where there's a defined landing surface, with HLS there's a non zero chance there might be some horizontal speed component at touchdown. Propellant sloshing as well.)

@DemoR Год назад

In this case you'd also have to look at fuel slosh. Speaking of which, this gets me thinking about how you would do a long duration lunar mission with lunar starship. I doubt they can keep the tanks at the right temperature for weeks on end.

@lazarus2691 Год назад

@@DemoR You probably can't keep the heat out entirely, but if you can insulate the tanks enough you might be able to reach a level of boiloff where you can trade payload mass for longer durations. I.E , say you lose 1 tonne of propellant per day to boiloff. If you want to stay for 20 days, that means you'd need an extra 20 tonnes of propellant vs just touch and go, which means you have to trade off 20 tonnes of payload to make up that deficit. Just spitballing here of course.

@EagerSpace Год назад

I thought a bit about that but didn't do any real work on it. The maximum horizontal velocity during apollo was less than a meter per second, and I'd expect that lunar starship would be better than that; I think they do much less than that with Falcon 9. My *guess* is that 1 m/s would be fine.

@EagerSpace Год назад

@@DemoR There's obvious no convection to worry about and the only conduction will be through the landing legs, so pretty much nothing there. So the only heating you get is solar, and with white paint that should be pretty minimal. Vaporizing the cryogenic fuels requires a lot of heat, so I think they will probably be fine there.

@williamcase426 11 дней назад

Oh no

@MrFranklitalien Год назад

the reaction wheels should be able to handle this :)

@SomeoneStoleMyHandleName 5 месяцев назад

Do the same for 70m height Starship V3 please

@EagerSpace 5 месяцев назад

Should be fairly simple given the information released.

@NorthernChev Год назад

You forgot about calculating the fuel that is used for backfilling ullage.

@phoule76 Год назад

I'm a spherical viewer (and liker).

@RoBear-xo6zw 2 месяца назад

Unlikely? Unless a leg were to fail 😂

@OliverTheSpaceNerd Год назад

Cool

@garysantos7053 Год назад

It's not will it fall over; it's when it falls over, "Then what will you do."

@donjones4719 Год назад

While we're discussing Starship and the Moon - could you do a video on Starship alternatives to SLS/Orion? Your ability to give hard figures and clearly spell things out is sorely needed for this. I've seen a proposal on reddit that a lightly loaded regular Starship with a crew compartment could go to NRHO and back *without needing refilling* in NRHO. Not needing a refill is necessary for this to be considered in the near- and mid-term by NASA. The crew compartment for 4-6 can be based on the one for HLS, ergo NASA approved. A light load of cargo will be fine early in the program. Heavy cargo-only runs can be done separately. I hope to see this done at about the time of Artemis 4 so a crewed launch on the Starship isn't included. Crew would launch on a Dragon and board the refilled ship in LEO. The return of the crew will require a bit of a kludge. A stripped down Dragon is stowed in the cargo bay at launch and only deployed when the Starship is closing in on Earth. The crew deploys in this and enters the atmosphere & splashes down conventionally. The ship lands autonomously. A stripped down Dragon needs no SuperDracos and only minimal Draco propellants, along with minimal ECLSS and a stub trunk - all just enough for a few hours. Carrying this all the way to the Moon and back is certainly a bad looking kludge but is the most straightforward way to make NASA happy about a crew-rated reentry. Even SpaceX may not have crew-rated it by the late 2020s, Elon wants a couple of hundred successes *in a row.* A good enough solution that saves us billions by replacing SLS/Orion ASAP is preferable to a best solution later on. All this would be easier if this Starship could carry enough propellant to and fro that would allow propulsive deceleration to LEO. However, I'm informed on reddit that the delta-v doesn't work out. This LEO-to-LEO proposal is made repeatedly, though, so it will be great if you can definitively disprove it, put a nail in its coffin. Some guy on reddit has given answers to parts of this. Some guy named Triabolical.😉 I'm sure this looks familiar. A full-blown video will be so, so much better. If it helps, I just subscribed.

@EagerSpace Год назад

It's on my list of topics to explore. It seems fairly simple to do it one-time, but the hard part IMO looks to be figuring out reuse for the lander; getting fuel out to NRHO to either do another landing mission or come back to LEO looks challenging. Not sure when it will show up. I work on videos until I get bored, stuck, or aren't sure what my opinion is, and then I'll switch to something else. Or - often - I'll be working on one video and it turns out I need to do another one first; this video came out of a video on using starship as a habitat.

@donjones4719 Год назад

@@EagerSpace "It seems fairly simple to do it one-time". I'm afraid I don't see what you mean. The Dragon to LEO is reusable, the Starship for the round trip is reusable (it lands itself autonomously after the crew deploys in the capsule) and the stripped down Dragon can be reused. (It will of course have an upgraded heat shield.) Yup, filling in space (LEO or NRHO) will be a hard nut to crack. Doing it just in LEO will be hard, and Artemis can't go forward without it. And the chain of tanker flights to get a significant amount of propellant to NRHO will need Musk's vision for Starship's high flight cadence to make it work. That's why I use the kludge of a stripped-down Dragon and no NRHO refill - I see it as an interim solution until Starship is human-rated or NRHO refilling is perfected. Thank you for engaging. I certainly understand the need to be motivated when one is doing a project voluntarily, I've been there. But Christmas is coming... :) And besides me there are so, so many people looking for the LEO-to-LEO answer. You, sir, have a moral obligation to all of humankind. :D

@EagerSpace Год назад

@@donjones4719 When I said "fairly easy" I was referring to the artemis architecture where you go LEO => surface => NRHO and then leave it there. I will take a run at it, and we'll see what pops out. Refueling probably complicates the number of approaches. And I suspect there's an approach lurking out there that involves leaving the starship on the moon; I'm not sure taking 50 tons to the moon and taking a fair bit of it back makes a lot of sense. Or maybe there are just cargo variants that carry more. > You, sir, have a moral obligation to all of humankind. :D LOL. I shall therefore endeavour not to fail in this quest.

@donjones4719 Год назад

@@EagerSpace Multiple thumbs up. And don't worry about refilling scenarios for my sake. We have to take it on faith the initial LEO depot filling->HLS ship can be done, per NASA & SpaceX & their current HLS plan. It follows that my Starship can get its LEO filling the same way and then need no others. Elaborating your video to NRHO fillings would be gravy, don't let it bog you down if it becomes burdensome.

@muuubiee 2 месяца назад

This felt rushed? We're not consider the softness of the moon soil we land on. The descent profile matters too... Unless it halts all horizontal differential speed and lands with none of it, it'll have momentum in some direction. Gravity being so much lower than on earth, this makes way bigger of a difference. Based on pure speculation. I'd want to see falcon 9 land on a grass field, or on sand, as that's what I'd expect to be what landing starship will be like.

@ramilv739 Год назад

'Lokhotron' 😂

@NorthernChev Год назад

Starship cannot land and still stay standing safely at 20 or less degree angle. As soon as you open the cargo bay doors and start lowering cargo from the nose, you're putting weight outside that 20° angle.

@TheEvilmooseofdoom Год назад

Yeah, and lowing it, which makes it even more stable.

@ThomasHaberkorn Год назад

yes if pushed by a giant

@user-kv5fw7xz9c Месяц назад

I like math and rocket science.

@yeetoburrito9972 Год назад

Instructions unclear. Where should I put my 135 CCs of chicken broth? I tried injecting the quail eggs but that didn't work... Regardless, great video!

@EagerSpace Год назад

Proper execution of the instruction is left as an exercise to the viewer...

@justinwhite7183 Год назад

It’s not going to the moon

@sonofamortician Год назад

can they not map the height at each leg as it descends and mechanically adjust the legs height for standing position, using actuators to either telescopically adjusting the length or using pistons the angle, a bit how a four legged robots cybernetics will autobalance, Personally I think as long as the landing spot has been vetted in advance by orbital drone this shouldn't be a big problem as a suitable site can be selected, I am far more worried about regolith kicking up when taking off and breaking a thin pipe or the engine bell, or even just blocking some of the outlets with regolith.

@TheEvilmooseofdoom Год назад

Yes, the landing legs can self-level to a degree. Regolith will be moving away from the ship when the engines are firing, not towards it.

@sonofamortician Год назад

@@TheEvilmooseofdoom this actually happened with the martyte concrete platforms while they were testing SN8, they have covers now, but still...