Worth noting is that because Starship HLS carries astronauts, it has to be capable of abort-to-orbit -- that is, to cancel the landing at any point and return to Lunar orbit. The Apollo LEM would have done this by shutting down and dumping the descent stage then lighting the ascent motor: Starship is a single stage that should have enough fuel and oxidizer left after a successful landing to lift off and return to orbit with a minimal payload.
I expect if astronauts aboard HLS lose their altimeter they'd have to abort the landing immediately -- to proceed without it would be the height of recklessness. But Odysseus had no abort-to-orbit capability so was committed to landing.
Huh, then you're one of today's lucky ten thousand!
Apollo 14 had a piece of loose solder in the button triggering abort-to-orbit, so it occassionally triggered itself. This wasn't a problem en route to the moon, but the second the descent phase started it would have been a Poisson-timed bomb that would prevent the landing.
There was a bit of memory that could be set to ignore the state of the abort button (this bit was the reason the abort sequence wasn't triggered en route). The problem was this ignore bit was reset by the landing sequence (to allow aborting once landing started), and they did not believe the astronauts would be quick enough to set the bit again before the button shorted out and triggered the abort.
(Ignoring the abort button was fine because an abort could be triggered in the computer instead. Takes a little longer but was determined a better option than scrapping the mission.)
Don Eyles came up with a clever hack. Setting the program state to 71 ("abort in progress") happened to both allow descent to start and prevented the abort button from being effective. So this program state was keyed in just before descent.
The drawback was that it obviously put the computer in an invalid state so some things were not scheduled correctly but Eyles and colleages had figured out which things and the astronauts could start those processes manually.
Then once the computer was in a reasonable state again the ignore abort bit could be set and the program mode set correctly and it was as if nothing had happened.
>I have never once read about abort-to-orbit capability as a concept
ATO was an abort mode [1] on the Shuttle program and is notably the only abort mode that was successfully used in the entire program, on STS-51f [2] . Challenger suffered an engine anomaly on liftoff that resulted in a lower orbit than was intended, but otherwise the mission went off without a hitch.
Thanks! I’d seen about the bailout capability mentioned in passing, but had always wondered what it would be in practice (spoiler: a pole!). Also, I didn’t realize a second engine almost shut down on STS-51-F .
Per the links:
“A particularly significant enhancement was bailout capability. Unlike the ejection seat in a fighter plane, the shuttle had an inflight crew escape system[12] (ICES). The vehicle was put in a stable glide on autopilot, the hatch was blown, and the crew slid out a pole to clear the orbiter's left wing. They would then parachute to earth or the sea. […] Before the Challenger disaster, this almost happened on STS-51-F, when a single SSME failed at about T+345 seconds. […] A second SSME almost failed because of a spurious temperature reading; however, the engine shutdown was inhibited by a quick-thinking flight controller. If the second SSME had failed within about 69 seconds of the first, there would have been insufficient energy to cross the Atlantic. Without bailout capability, the entire crew would have been killed.“
It's doubly confusing that STS-51-F, with the Challenger, is the only exercised launch abort; while STS-51-L is the famous launch disaster for which Challenger is most well known.
> “As a result of the changes in systems, flights under different numbering systems could have the same number with one having a letter appended, e.g. flight STS-51 (a mission carried out by Discovery in 1993) was many years after STS-51-A (Discovery's second flight in 1984).[6] It wasn't until STS-127 in 2009 where the flight numbering system returned to a standard and consistent order.”
Ouch, shortly after they get standardized and consistent flight numbers, the shuttle program gets cancelled. I guess computer science doesn’t have a monopoly over the difficulty of naming things.
Among last-ditch options considered for the Apollo programme (specifically several planned but eliminated long-duration, two-week missions), was the ultimate LESS-is-more approach: "Lunar escape systems".
This was basically a lawn-chair rocket for two which would utilise a disabled LEM's (lunar excursion module) fuel tanks, and would be hand-piloted without any guidance computer to an intercept orbit with the Apollo Command Module, with the hope that a rendezvous and crew transfer could occur within the four-hour window of space-suit oxygen supplies. Given that the CM's orbital period was two hours, this meant at best two chances for a successful intercept.
(I'd run across this from the recently submitted MOOSE article, "Man out of space, easiest", a strap-a-foam-mattress-to-your-ass reentry concept: <https://en.wikipedia.org/wiki/MOOSE>.)
Apollo Lunar Module had an abort-to-orbit that was also used to lift off the surface of the Moon after successfully completing the mission. It used explosive charges to throw the lander frame away and involved Apollo Guidance Computer manuevering into orbit at any point of the mission up until the landing.
Dragon 2 has abort to orbit capabilities, too. The abort zones they call out as the rocket's IIP advances up the east coast continue until Ireland, and then after that, it's abort to orbit, where the superdracos will carry the ship to orbit without the second stage.
Abort-to-orbit is a confusing term since it suggests the Shuttle's specific ATO mode. I presume the requirement is "safe abort at all points during lunar descent/landing" rather than specifically to orbit (e.g. an abort mode that put them directly on a return-to-Earth trajectory would probably also be fine).
Sure. I meant more generally, presumably NASA's requirement is "has an acceptable plan to safely return them to Earth after abort" rather than specifying particular orbits.
I think since then Elon has mentioned that abort via the main Starship engines may be possible through all points of a launch (putting aside the landing process for now). Probably also helped by the hot staging related changes, since IIRC the concern regarding abort modes was whether or not the engines could safely ignite and separate from the booster.
It does still leave the system without a means of aborting if the ship's main engines have trouble, although I suppose they do have a good bit of redundancy there.
I expect if astronauts aboard HLS lose their altimeter they'd have to abort the landing immediately -- to proceed without it would be the height of recklessness.
In addition to the obvious, it should be taken into account that the absence of atmosphere makes very difficult to assess distance and scale. Videos of approach seem like a fractal browser.
I think GP was saying that the lander is single-stage. By the time of a presumptive lunar landing, there's no lower stage to drop as with the Apollo LEM.
Assuming the landing is soft enough to survive, shouldn't it be fairly trivial for the astronauts to disembark and right the lander? To the extent anything in space is trivial.
Even if it's a bit more than doable by hand a ratchet jack should make short work of it.
The Apollo LEM, only craft that has ever taken humans to the moon's surface, weighted somewhere around 20,000 kg after landing. Since it only ever operated in space and lunar gravity, it could be built with a much higher mass fraction than a rocket launched from earth requires - greater than 30%, where a Falcon 9 in comparison has a mass fraction below 5%. Even then, the LEM structure had to be built incredibly lightly. While the LEM structure could obviously be lifted by crane and survive launch and docking stresses, those were are at designed points in the structure. Without the presence of a crane capable of lifting the whole LEM, righting an LEM that had landed on its side would have been effectively impossible. Basically all of the modern proposed manned lunar landers are considerably larger than the LEM, and thus considerably heavier.
For comparison, a craft built for earth launch mass fractions probably wouldn't survive falling over in the first place - when that happened to a Falcon 9, the whole rocket simply exploded.
>shouldn't it be fairly trivial for the astronauts to disembark and right the lander?
I don't think that is an assumption you can make. In the worst case scenario the lander lands on the door. In which case the only way to disembark is to lift the lander.
Yup, jack points in the right place, jacking equipment with sufficient range of motion, AND solid lunar soil in the right place under the jack points.
Plus, you've got to get the whole jacking operation done without damaging any of your main or control thruster rockets, and without tipping past the upright point over to the other side, or just effectively rolling onto an adjacent side.
I wouldn't want to go on a craft where [jacking it back upright] was in the top ten on the list of recovery options to get home.
All the extra mass budget would likely be better spent on a more robust attitude control system to avoid flopping over in the first place. Unless you need it for something else anyway.
>I wouldn't want to go on a craft where [jacking it back upright] was in the top ten on the list of recovery options to get home.
For a counter, I wouldn't want to be on a lander so fragile[0] that being manipulated upright is infeasible. Something will go wrong, maybe not on that lander, but when it does go wrong it'll have to get duct taped together.
[0]Not just mechanically, but in terms of operation scope. Planning that everything must go perfectly or people die is a recipe for the latter.
I deliberately did not say I wanted jacking to be infeasible — but I DO want it quite far down on the options list, as in there's >10 better things to try first.
(And yes, I've done a fair amount of wrangling vehicles, gear, etc. in snow, dirt, mud, & rocks, and eventually it can often be gotten out. But on a different planet/moon, it really should be not be anything close to a primary option. OTOH, if it's got a set of 6+ pop-out lever-legs to upright itself, tested, etc., that's a different solution)
agree - which is probably why Elon Musk is so obsessive about increasing the efficiency and thrust of the merlin and raptor rocket engines, a huge amount of downstream capability can be achieved by increasing that number (all other things being equal)
So if the lander falls over because two of the feet land on regolith, odds are good you don't have a solid point on that side of the craft to put the jack...
Astronauts must be nervous stepping onto the first manned flight of a new craft that has a 100% success rate in the sole previous flight, but might have only a 50% success rate by the end of their mission...
With both Crew Dragon and Starship, there will have been _many_ successful missions involving un-crewed variants of the spacecraft (Falcon 9 and Cargo Dragon were both well-proven systems before crew was a possibility).
Well at least they would have no one else to blame but themselves. As far as I remember it was the pilots that insisted on the shuttle to be not be 100% automated, so they had to do it this way. The soviets just made the whole shuttle automated so it could be tested without risk to crew.
Almost all challenges are caused by tight mass budgets--the maximum mass that we can get to the lunar surface. Symmetrically, almost all problems can be solved by increasing the mass budget: more fuel to loiter longer, redundant systems, etc.
The advantage of SpaceX's Starship--and the reason NASA chose it for the first HLS--is that it has an insane mass budget. It's literally designed to land 100 people on the surface of Mars (TBD whether it will ever meet that goal, but that's the design point).
Starship is so hilariously large that there's enough mass budget to solve almost any problem.
That's incorrect -- the reason NASA chose Starship is because it was the most capable lander for the lowest possible projected upfront cost. Government contracts always attempt to maximize economic utility while meeting objectives -- any other advantages are ancillary to this.
> Symmetrically, almost all problems can be solved by increasing the mass budget: more fuel to loiter longer, redundant systems, etc...Starship is so hilariously large that there's enough mass budget to solve almost any problem.
Also incorrect. Mass budget does not change fundamental Newtonian physics, nor does it alter the issue of instability caused by a high center of mass. The engineers at SpaceX are very smart and I'm sure they're hard at work trying to engineer out this solution, but it's a bit like saying that you can prevent a car from rolling over if you make it heavy and powerful enough. Sure, but that causes problems and challenges of its own. It would have been easier to engineer the car to have a lower center of mass, i.e. it would be easier to land on the moon with a lander that had its mass spread out over a larger surface area and didn't have an angular moment of inertia significant enough to where topple was a concern -- like the Dynetics or BO proposals.
> Also incorrect. Mass budget does not change fundamental Newtonian physics, nor does it alter the issue of instability caused by a high center of mass.
The size of the ship solves some problems. Illustrations depict landing gear taller than a person, which means small rocks and holes are less of an issue.
Landing on a sloped surface will be an issue. Apollo 15 was close to disaster on its tilted landing and Apollo 12 had a bobble when setting down. Starship is unlikely to survive the same.
Starship will have spare fuel and relightable engines. It could just take off when it starts tipping and go for a second landing attempt on a more even surface. The low gravity is a real pain for landing, but it makes it really easy to abort a landing too, even after touch down.
Except they have no depth of experience doing a non-hoverslam landing (0 on dirt) and there is a serious risk of damage from flying debris. Apollo only had 2s max to perform an abort on a known good engine. Expecting a restart to work reliably with minimal delay is ambitious.
> It could just take off when it starts tipping and go for a second landing attempt on a more even surface.
... A surprisingly kerbal solution. Wouldn't the engines be firing to control the vertical speed though? Otherwise it'll end up lithobraking at hundreds of meters per second instead of gently touching down at 1 or 2 m/s. At least that's what happens to me if I don't burn retrograde.
> Lets not go overboard with the claims we make about government contracting.
That's more or less true though?
There's no need to debate semantics when the criteria NASA used are very clearly laid out in the source selection statement [0]. It is plain that SpaceX was selected because it met the technical requirements, provided the best value for the government, and fit within NASA's budget for the program (indeed, was the only proposal that did so).
There's also the GAO report which more or less says the same thing with more detail and confirms NASA's judgement [1].
And, I'm no expert on contracting, but it is my understanding that "meeting requirements" and "achieving the best value" are criteria that are supposed to underpin all government contracts, not something unique to that particular contract.
No it isn't. It was done correctly in this case. But if you study the history of NASA and DoD contracting the idea that they always perfectly evaluate is nonsense.
Literally during the very selection process you talk about, a NASA employ was fired because he tried to give Boeing an unfair advantage. How many times in history was this not caught?
Often the selection documents aren't public. The idea that lobbying and politics have no influence of government selection is just being naive.
Just recently in commercial Crew Starliner was selected over Dreamchaser. Despite Dreamchaser being considerably cheaper, and offering much more utility. NASA just assumed that Starliner would be done fast because it was Boeing. The reality many believe without Boeing CommercialCrew would have failed.
We can go threw history, as far back as you like. The Supersonic transport, you basically had Boeing proposing an absurdly complex incredibly ambitious design, despite being the company with the least amount of experience. They were selected despite the other projects being much more reasonable and much cheaper.
>understanding that "meeting requirements" and "achieving the best value"
These can often be at odds. It is surprisingly difficult to award a govt contract under the guise that it provides better value (and there are specific contract mechanisms to that effect). However, from a contracting officer's perspective, it can be riskier (to them personally, even if it's less risky to the taxpayer). The govt also has other goals, like reducing the risk of putting all their eggs into one contractor's basket. All this to say, there are enough competing aspects to undermine a claim that "value" is baked into the primary goals of every contract.
The Saturn V could get a lot of mass to LEO but most of that mass was fuel to get from LEO to the surface of the Moon. A design caveat of SpaceX Starship (a design feature that's yet to be demonstrated/proven) is refueling in LEO. So the Starship gets a bunch of payload mass to LEO, refuels, and then heads to the Moon. For Mars it would need to refuel on Mars to get back to Earth.
It's the refueling that potentially gets a huge usable payload to the Moon. A second Starship whose only payload is fuel would launch with the first and they'd rendezvous and transfer fuel. Ostensibly if something went wrong with the refuel rendezvous the payload (or personnel) carrier would still be able to abort back to Earth.
This is the huge difference. Apollo missions used two launches of the Saturn V - one for the crew capsule and one for the lunar lander, which rendezvoused in orbit. Artemis is planning on using one SLS launch for the crew capsule, and an estimated 8-16 Starship launches for the lunar lander and refueling.
That isn't how the Apollo missions worked. They put the command module, service module and the LEM on a single Saturn 5[1]. Once in space, the command+service module would need to turn around and dock with the LEM before heading off to the moon.
> Apollo missions used two launches of the Saturn V - one for the crew capsule and one for the lunar lander, which rendezvoused in orbit.
That was a concept called "Earth Orbit Rendezvous" which was discarded early on during the Apollo program in favor of "Lunar Orbit Rendezvous" where the Command and Service Module (CSM) and the Lunar Module (LM) was launched on a single Saturn V. You can see this in the movie Apollo 13.
Starship gets refueled in orbit (by a fleet of Saturn V-class rockets). A Saturn V could put about 8 metric tons on the lunar surface. With refueling, Starship can land 100 metric tons on the moon.
That's a matter of some debate. Somewhere between 6 and 12, I believe, is the range.
SpaceX plans to stretch the second stage to increase fuel carrying capacity for tanker flights, so the actual number is TBD until both the revised Starship and its engines (Raptor 3) are built and tested.
It depends on how many Starships you can launch simultaneously, because the time the fuel depot spends in orbit determines how much fuel is lost to boil-off. If you have a serial launch architecture, assuming reusability, refuling and relaunching, then the upper bound is around 20 launches. Even with expendable Starships, this is still cheaper than SLS, but not by much... This is why reusability is critical to the mission.
You mean it wasn't because Kathy Lueders had a heavy bias towards SpaceX (she now works at SpaceX) to the point where she forgot to select a second commercial partner for the Artemis missions? When Blue Origin was suing NASA, they were primarily pointing out Kathy Lueders' gross incompetence during the procurement process.
It's kind of weird that someone would select a launch architecture that is meant to go to Mars and whose company CEO thinks the moon is a waste of time for a moon mission. Yeah sure, SpaceX is going to Mars, but are they going to the moon?
Considering the massive delays at SpaceX, their Starship will turn into another SLS type boondoggle. At the current rate of development, it is not obvious that the schedule of Artemis 3 is going to be meaningfully ahead of Artemis 5. If it takes Blue Origin 2-3 years to launch their New Glenn rocket, then all they have to do is build the lander and they are pretty much set, because it only takes 3 New Glenn rockets, which could launch simultaneously to minimize time in orbit and thereby reduce boil off. Reusability is a nice to have cost optimization for Blue Origin. When it comes to the Artemis 3 architecture, it is impossible to stay under $1 billion per launch without some form of reusability.
They hadn't selected a second commercial option at the time because they were barely given enough funding for one lander, and all the other proposals wanted a ton more money. They only chose the second option when Congress finally allocated more funding for the program. Congress effectively made Starship the most appealing choice and then complained when their MIC masters didn't get chosen for their 60s era designs.
Also, it's ironic you're saying that BO could do it faster, their lander is basically just a Hydrogen fueled Starship.
a) for launch you want your rocket to be slender and tall. For a stable landing you want your vehicle to be broad and flat.
b) The engine is at the bottom (moon-wards), by definition. The fuel is above the engine. As you land, the fuel tank depletes significantly which shifts the center of mass towards the top of the vehicle which makes it less stable.
c) The lunar (mun-ar?) surface is really uneven and gravity is low. What you want to land is a steamroller but what you actually have is a springy, ultra-light, top-heavy contraption that's more likely to bounce off of then to flatten moon rocks.
> As you land, the fuel tank depletes significantly which shifts the center of mass towards the top of the vehicle
Genuinely asking because I think I might learn something: wouldn't a depleting fuel tank above the engines shift the center of mass toward the bottom of the vehicle?
Generally, a good spacecraft has the least amount of mass possible on fuel/engines as compared to payload (the useful part of a mission) which is why center of mass either migrates upward or stays mostly neutral.
I don't think this is right. My understanding is that the engine is typically the one of the heaviest dry parts of the vehicle and the fuel (at launch) the heaviest individual part overall. Especially nowadays since the electronics and sensors are tiny and antennae are lightweight.
This is especially the case with things like landers and geostationary satellites, where you want as much fuel as you can afford for station keeping, to keep the satellite operable for as long as possible.
Half of Nova-C's mass was fuel (~900kg), payload was 100kg. Starship's payload is ~100t, dry mass is ~150-200t but fuel mass is ~1200t.
It makes sense that the engines would be heavy and they are heavy on the launch vehicle. I am not sure how the ratios come out there but I'd still expect the fuel to, by far, take up most of the mass. Then engines for maneuvering in space and to land on the moon don't have to be very big. I looked up the figures for Apollo and found out the following:
"The Apollo's "lunar module descent engine" weighs a mere 180 KG vs the approx. 4200 KG of the rest of the craft (dry mass). Just the fuel for the descent is then roughly 8000 KG."
WRT b: surely using fuel that is above the engine will bring the centre of mass down, because the engine's mass is still there with less fuel mass above it?
Unless the rest of the vehicle's mass (all the other equipment, and crew if it is a manned mission) has more mass than the engine & landing apparatus of course, which I think (caveat: no deep thinking involved here) is likely for manned missions but less so for others? I'm assuming the mission mass is above the fuel (having the fuel on top would presumably be less safe/reliable/practical/other).
I could easily be wrong and I am very open to learning as what I wrote is just my intuition developed from playing KSP.
The Apollo's "lunar module descent engine" weighs a mere 180 KG vs the approx. 4200 KG of the rest of the craft (dry mass). Just the fuel for the descent is then roughly 8000 KG.
Obviously, landing on the moon is possible but I do think that the inherent requirement to have engine(s) and fuel tanks below the payload makes landing in a vacuum a bit of a challenge.
I'm fairly certain that the effect of point b is just a version of the pendulum rocket fallacy. There is actually no change in stability of a rocket in flight related to if the engines are on top or on the bottom because the tidal forces exerted by gravity are too negligible in that specific case and otherwise gravity is acting equally on the entire body.
Plus, since the engine is typically one of the heaviest parts , and the lander isn't a two-part design like Apollo, the fuel tanks are mostly empty upon landing, and therefore the center of mass is low due to the engine.
Edit: thanks to commenters for the reference to KSP. I had to ask Wikipedia what it is, and the first sentence is: "Kerbal Space Program (KSP) is a space flight simulation video game developed by Mexican studio Squad".
Mexicans forgetting about Latin is even worse than native English speaker doing the same!
It wasn't a mistake. KSP takes place in a solar system that is similar, but not identical to our own, and the planet the the space center is on, Kerbin, has a moon, called Mun.
No, CM shifts toward the bottom, especially while the engine is thrusting and the craft is upright in lunar gravity. The liquid methane and O2 slosh toward the bottom of the tanks in those conditions.
The spacecraft failed long before it tipped over. With the altitude laser system out of action, it wasn't going to land correctly unless they got lucky, which they didn't.
Like the article said in the last line, the margin of error is only manageable if all the systems are functioning correctly. The argument over the height of the lander is as nonsensical as arguing over any of the thousands of other design decisions. Second guessing literal rocket scientists is silly.
The lander was designed as a whole, any single change - redundant systems, extendible legs, etc., etc. - would have required other changes due to weight or space constraints, requiring other changes, ad nauseum.
The specific thing that killed this landing is a failure in quality control/checklists which if done better would have ensured all the systems operated correctly and a successful landing.
Dynetics’ proposal was the most expensive, and they also couldn’t figure out a way to make it work at the time when the choice was made[1]:
> Of particular concern is the significant weakness within Dynetics’ proposal under Technical Area of Focus 1, Technical Design Concept, due to the SEP’s finding that Dynetics’ current mass estimate for its DAE far exceeds its current mass allocation; plainly stated, Dynetics’ proposal evidences a substantial negative mass allocation. This negative value, as opposed to positive reserves that could protect against mass increases at this phase of Dynetics’ development cycle, is disconcerting insofar as it calls into question the feasibility of Dynetics’ mission architecture and its ability to successfully close its mission as proposed.
You can read NASA’s full thoughts on that link. But the basics are, they thought there were good ideas, but they weren’t comfortable picking a lander that went far above the allotted budget, while the team who made the lander wasn’t able to come up with a way that it would work yet.
IIRC the original Dynetics proposal had a positive mass allocation, but it relied on refueling at the Artemis Lunar Gateway. NASA then changed the requirements so that the Artemis Lunar Gateway would not be fully available for the first moon landing, and Dynetics was unable to adapt their proposal.
More power to you, but I've had multiple munar landing attempts turn into munar rescue missions precisely because the first mission lander tipped over :D
“Intuition that’s based on Earth is now a liability,” Dr. Metzger said. He gave the example of trying to push over the refrigerator in your kitchen. “It’s so heavy that a slight push is not going to push it over.” But you replace it with a piece of Styrofoam in the shape of a refrigerator, mimicking the weight of a real refrigerator in lunar gravity, “then a very light push will push it over.”
When landing, the horizontal velocity (side drifting) should be very very minimal, otherwise it would topple over.
That shape must be patented or copyright protected, because all the Amazon listings are several hundred dollars each. The usual knockoffs are conspicuous in their absence.
Indeed. The Wikipedia article says: "The gömböc, as the first physical example, is less sensitive; yet it has a shape tolerance of 10−3, that is 0.1 mm for a 10 cm size."
With a lunar lander you can play with the weight distribution. You can make it more dense on one side. This, together with a self-righting shape, could increase the chances of settling in the desired orientation.
While it was settling it would destroy all/most of the external fixtures including antennae, engine nozzles, and sensor housings. Bonus the rocking action during settling could puncture the hull or break a windows on a sharp boulder.
What if airbags inflated around the lander? The external shape of the lander-with-inflated-airbags and the internal weight distribution could make it self-righting, while shielding the external fixtures and the hull.
Just throwing ideas around and role-playing spacecraft designer.
Well, it's an example of a convex homogeneous body that does this. It's much easier if these are not requirements, just have a sphere with an off-center mass.
That's how the earlier Mars rovers arrived, totally valid concept. But it's expensive to get mass to the Moon, and if you think you can likely land upright with thrusters, why bother with something more complex/massive?
I saw a diagram of a lander, maybe just a prototype, that was constructed like a truncated tetrahedron. It would end up on either the bottom, or one of three sides. Once it landed the three sides would open up. no matter which orientation, that would push it to an upright position.
It was because of weight constraints. Spirit and Opportunity weighed 185 kg, while Curiosity and Preseverance both weighed around 1000kg. At that weight airbags large enough to cushion down the payload sufficiently would weigh too much. Just look at how large the spirit airbags were to support a rover that was only 1.5m square.
isn't regolith microscopic and sharp? A sealed ball that rolls around is one thing, but wouldn't a non-sealed ball just get its motor shredded pretty quickly?
I remember reading before that given the consistency and weight of moon dust that electrostatic protection of assets is viable.
I guess the concept would be to surround the motors in a electrostatic force that results in propulsive removal of particulates away from the drivetrain.
You can. But landing isn't the only issue. You have lots of things you need to take into account.
For example, at some point you need to be in the right position for your communication and power needs. The payloads need to handle rolling around. Lots of reasons.
Its a very invasive solution for one particular problem but doesn't help and makes other things harder. If you don't slow down, being round want help you when splatting on the ground.
At the end of the day, we can make landing of the moon reliable with other methods that are less invasive and thus less costly. The solution you suggest is one that you use if you don't have any good options left.
Maybe before sending lots of landers we should build a moon GPS system for guiding to a precise safe landing spot?
But it also occurs to me and therefore probably the actual engineers they should be throwing these landers out of an airplane over a rough, rocky earth desert many times before trying the moon?
Keeping satellites in orbit around the moon is very expensive. The moons gravity is lumpy, and if you try to orbit far enough that it balances out, then perturbations from the earth and sun still end up destabilizing it. This means it takes a lot of station keeping (firing thrusters, using limited propellant) to maintain an orbit.
I think there are plans for better relays situated around the moon, but a lunar gps system is not likely given the costs and engineering difficulties.
If they could get the budget to build a few extra multi million dollar spacecraft and throw them in the sand they absolutely would. Unfortunately all management gave us were these cardboard boxes with a lander drawn on them in sharpie so we'll have to use our imagination.
It seems both of these landers fell over due to instrument failures. So o solution that relies on building different instruments is not obviously the right one.
Celestial navigation only gives you attitude information while in space. The video is talking about aligning the guidance systems with the celestial coordinate frame. The stars are far enough away that it is not possible to get absolute position/velocity information using the stars (unless you use some near-future tech like XNAV, https://en.wikipedia.org/wiki/Pulsar-based_navigation). Of course, the position of the planets can give you general idea about what "side" of the solar system you are on. A star like Polaris can give you a rough idea of latitude, but that is not nearly enough precision to perform a planetary landing.
The Surveyor probes used radar ranging to get relative altitude/velocity measurements. They were not very precise in where exactly they landed. The Apollo landers were semi-manually flown visually in the terminal guidance phase which probably helped with their accuracy.
The vision-based systems used today are much more capable of doing precision landings autonomously once you are close to the surface.
I think the stars, in conjunction with the planets, can give you a half decent fix.
The Soviets started landing on the moon in the 1950s. It wasn't pretty, it was primitive, but it has been done. We (as a species) have since landed on asteroids and planets of sulphuric acid.
Space is hard, but we're literally trying to replicate what has already been done.
> I think the stars, in conjunction with the planets, can give you a half decent fix.
What was lacking then was precision. The landers from the 60s (Soviet and US) targeted landing areas that were massive. You basically ensured that the initial descent trajectory would intersect a certain area (using ground-based orbit determination) and the terminal landing sequence just ensured a soft-landing ... wherever that might be.
What is even more impressive is that they did all that without any digital computer on board. For example, in the Surveyor lander, the landing guidance was made up of analog electronics, using the radar signals to command a thrust-vector and throttle to the gimbaled rocket engines. Here is an interesting read about NASA's surveyor probe, if you want to know more: https://www.sciencedirect.com/science/article/pii/S147466701...
In contrast, the new commercial landers are trying to land at very precise locations within hundreds, if not tens of meters of a certain point. And they are doing that with a fraction of the budget of the programs from the 60s. For example, the entire Surveyor program (with 7 landers) cost ~$469 million in 1966. That is nearly 4.5 billion in 2024 dollars with a large part of that going into R&D. The IM-1 lander in contrast, was awarded $118 million. The Japanese SLIM lander cost $121.5 million.
So for what they have, they are doing really well!
I wonder if anybody has thought about giving the lander a slow rotation? It will help stabilize its landing axis and so likely avoiding a tipping-over.
Another idea is to let the lander “spring” on the moon surface. Because the gravity is so small, a free fall from 50 m or so will be like nothing. Cutting off the engine early and accept a certain down fall velocity will help stabilize the landing axis as well. With a wider base, the landing can be further stabilized.
I think the former is avoided because attitude control thrusters don't tend to be very powerful, so you're adding another variable you need to zero out right as you land, and because sensors can't necessarily be rotated and still provide useful data.
Allowing the lander to take a bit of a hit is kind of what IM-1 ended up doing :P but jokes aside, the legs add a bit of tolerance for this, and it has been done on Mars (wrapping rovers in inflatable balloons to absorb the impact), but I guess the logic with the Moon is that you need to do a controlled propulsive descent anyway (and with heavy/large payloads you have no other options), so might as well focus on doing it properly. With Mars there's an atmosphere to help, reducing how controlled the descent needed to be for lighter things.
Radical suggestion. Don't make your lander taller than wide. I'm the first to assume that the science nerds have thought of everything and that my uneducated self has nothing to say about it. But then I saw the lander. It looks very tippable.
So then here's my luddite take. Can't they just unfurl wider stabilizers from the legs that increase their footprint? At slow speeds in low gravity it seems like they wouldn't need to be heavy or strong.
In general, when it seems to my uneducated opinion that a bunch of experts have missed something obvious to me, it's almost always the case that the one who has missed something is me.
I feel exactly the same and this is the reason why I would absolutely love to read an expert article titled "Why super-wide Moon landing gear is not a good idea"
Stabilizers are made of matter, and matter has mass. Lifting mass off of the Earth and on to the Moon takes fuel. Fuel is made of matter too, and has mass. Lifting the fuel to lift the fuel to lift the mass is expensive.
So much cheaper just to have an altimeter and no extra stabilizers. Sadly, their altimeter didn’t work. They forgot to turn it on correctly.
Honestly, they’re lucky that it got so close to landing correctly; if it had been going faster the damage would have been even worse than just a crumpled landing leg.
What does "on the side" mean? A controlled landing surely means the engine points down and has some element of lateral control to achieve some stability. If relative to the engine you land on the side, that's an uncontrolled crash, not a controlled landing.
To me it means landing on the wider side. Take a pencil. If landing on the longer side is easier than the thin side, land on that one. Use some valves, it’ll be fine
TIL the lunar lander for Artemis is 100 TONS! My goodness! I didn't think it'd be the Mylar balloon of the Apollo LM, but I did not really think it was going to be the entire first stage of Starship. I guess I need to read more.
Maybe for a small lander, an alternative to landing upright would be to avoid having an upright in the first place. Have a spherical/polyhedral design with legs on all faces and redundant solar panels/cameras on each face.
Very easy solution until you realize you need solar panels facing the sun[1], radiators facing deep space[2], antennas facing earth, payloads facing x, y, and z, deployable payloads facing x, y, and z plus the lunar surface. And all of those things are fragile, at least in terms of mounting them on the outside of a bowling ball rolling across sharp gravel/sand. And of course multiply difficulty by the number of all configurations^2 for both design and testing. [1] and [2] are especially huge drivers, you need power and therefore heat input, but you also need radiators to expel heat. Depending on complexity, solar panels in shade act as passive radiators leaking heat at best, and at worst as heaters, actively taking battery power to heat up and become even better radiators. And radiators act, to some extent, less effectively or even as heaters if they are facing the sun, sunlit earth, or sunlit lunar surface instead of deep space.
It's not only a matter of adding complexity, mass, money, etc. This kind of solution is simple on its face, but it is akin to being ignorant of why a car has windows (for the driver to see), doors (for the passengers to enter/exit) or a cooling system (to not overheat), and then reading that Jeeps (or to be more fair, a new Jeep prototype) are prone to tipping over on a trail after driving 1000km on a highway to a trailhead, and then commenting on how Chrysler should just make a dodecahedron Jeep with 20 wheels instead of 4.
These spacecraft also made it past 99% of the hurdles, the next try will probably make it and overcome the final 1% without starting from scratch and adding all kinds of complexity that are far more likely to add failure.
I work in the industry and opinions are mine and not of my employer.
I think the economics of a one-off lunar lander are a bit different to those of Jeep! The cost of the lander hardware is only a small part of overall cost of the mission, and adding some (or even a lot) of redundancy would seem a small price to pay if that provides a high likelihood of mission success. Of course this needs to be compared to cost and reliability of alternate solutions. This is a lot different to adding a lot of redundancy and cost and compromised design to a mass-produced vehicle where you can iterate and test in deployed environment as many times as you like.
Obviously N-way redundancy isn't optimal, but it would seem potentially simple if you had a modular design with multiple instances of the same "omniface" component. Perhaps use 1/2 of each redundant face for radiator and 1/2 for solar panel?
I'm not suggesting a rolling design - just one with legs on every side such that if it did tip over (or worst case tumble if landing on an incline) from preferred engine-down orientation then it would not make any difference.
Seeing as Intuitive Machines wanted to avoid deployable (spreadable) legs as a way to achieve a more stable low center of gravity, another alternative would seem to be to shrink the design (lose the height) to better work within the width of the faring, although I don't know how viable that would be given amount of propellant needed for the landing.
Cost of hardware is actually a huge part of overall cost, and the economics are worse, not better when you need to prototype and test things for a one-off mission/vehicle made by a new company vs updating a vehicle that sells hundreds of thousands, and making it by a company that has sold millions. There's virtually no technical risk in designing the next iteration of Jeep.
"Just put 1/2 radiator and 1/2 solar" and "just put legs on every side" is still really simplistic and nobody even mentioned thermal insulation yet, which is normally a much higher proportion of surface area compared to radiators and solar, at least if all three are on the main spacecraft body. I was being extreme in my last comment to make a point, but you still sound to me like a guy suggesting 20, and now 12 wheels on a Jeep instead of 4.
> you still sound to me like a guy suggesting 20, and now 12 wheels on a Jeep instead of 4
No - on a lunar lander, not on a jeep. It makes a difference (I'm really not sure why you started talking about Jeeps).
The difference is the cost to test a lunar lander (on the moon) vs cost to test a jeep, and the fact that we're only going to build one lunar lander vs a production run of millions for the jeep.
For the Jeep it's cheap enough to iterate and test (on earth), and end up with an optimized design that has 4 wheels and not 12 or 20. Not only is this relatively cheap to do, but there's a huge incentive to do so since we're going to mass produce the Jeep and would therefore like to reduce build cost and maximize profit.
In contrast, the lunar lander is very expensive to "test" since that means a failed mission to the moon. Maybe that mission costs $5M, so if we fail twice before getting it right we've added $10M to the cost. If we can avoid those failed tests by instead adding $1M of redundant hardware that makes it work first time, then we've saved a lot of money. We're only building one lunar lander, so there's no multiplier in front of that $1M we added to the hardware cost.
The first mars lander was in a tetraheadron in an airbag. There was no way for it to land in the wrong orientation because the tetraheadron always unfolded in the correct orientation. And that was almost 30 years ago.
Yes - that was a great design. I've seen some people suggest that it wouldn't work on the moon due to lack of atmosphere and less gravity, but not obvious why that would prevent it.
Of course it's a more complex design in a way given that you deploy this airbag at low altitude - something else to go wrong. It's interesting though that NASA has used that and the even more complex air-crane technique on Mars both successful first attempt. Even though they seem complex I'd assume NASA determined they were the least-complex approaches that had a high likelihood of success.
Maybe the economics of doing this on the moon, and with a cheaper lander, are different - better to have a simpler system with higher chance of failure, and redo the mission if it fails ?
Mars Pathfinder did exactly this. It was a tetrahedron which could land in any orientation. As it happened they rolled a 4, but if it was on one of the other 3 sides it would have pushed itself upright as the sides folded open.
It's super challenging when your ratio of height to width puts your center of gravity way up in the air, almost like the original moon landers where built squat and wide for a reason...
A spacecraft perhaps could inflate lots of impact balloons that would cushion impact, allowing landing in any orientation. Then on landing, rotate with gyros or something until the legs are underneath and that way end upright?
Humans did it manually in the 60's. How hard can it be to do it with computers and radar? I don't want to sound like that guy but... how hard can it be?
Edit: My point being: spacex is already doing it on earth, dealing with stronger gravity and air non linearity.
The IM-1 Lander was supposed to land using a LIDAR altimeter, but they forgot to remove the safety before launch. They tried to make a last minute software change to use an experimental navigation system from NASA to get altimetry, but this didn't work. So the lander landed using visual navigation and IMU data only for the last 15km to the surface.
It probably would have landed upright if the LIDAR worked. It is impressive that it landed as intact as it did
Because streets are not controlled environments. Planes have auto pilots for a long time, because air is a highly controlled environment with professionals agreeing to cooperate and making logical decisions (most of times).
I highly recommend taking a look at Kerbal Space Program plus k/OS. I've done a few Kerbal hackathons with friends where we all get the same spacecraft, in the same scenario, and have to write k/OS scripts to perform some mission. Difficult, but fun and often hilarious!
More seriously, the humans in question were very skilled pilots with huge amounts of general flight experience and specific lunar training; they also had access to hardware that had already been expensively tested in the lunar environment. Neither of those were available to this project.
The past few failed missions certainly highlights how amazing the successes the US had back in the day.
50-60 years of history, crazy advances in technology from materials to computers to everything else, yet its still objectively a difficult, "unsolved" problem.
Some Moon ideas:
1) have a small robot bulldozer flatten a landing pad/polygon so there is loads of safe landing area.
2) use same dozer to make a moon highway to other sites of interest around the moon.
3) Moon GPS or laser-based local navigation beacons, so the spacecraft can rely on those if instruments fail.
4) Just stupid-wide landing legs that let the craft ski around the moon even when landing at an angle and with horizontal velocity.
The Autonomous Site Preparation: Excavation, Compaction, and Testing (ASPECT) Project will develop tools and methods to clear, level, and compact the lunar surface. ASPECT is a fully autonomous rover with equipment for regolith excavation, boulder moving, and surface compaction.
There are a number of well fleshed out plans for doing essentially this. One of the more interesting ones for me was that microwaves can be used to fuse lunar regolith into a solid. One plan had a solar powered rover that sat there and microwaved the ground until is was solid far enough down, then would move forward on to that patch and start with the next patch. As I recall it would take about a month to make an acre sized "pad" which would support landing.
The reason Odysseus's legs are so narrow is that they wanted fixed legs, so there's no leg deployment that could go wrong. But payload fairings are only so wide. The legs are the widest that fit a Falcon 9 payload fairing.
I really like the idea of a mission to build infrastructure though.
Just like Canadarm ([1]) on ISS considerably simplified docking, I can see a similar approach working for lunar landing: slow down to below 5 m/s, get caught by a robotic arm and gently put into a good spot.
You know how the martian landers now use a crane to lower the lander to the ground so the retro rockets are outside of the ground effects range?
Someone proposed doing something similar with a lander, where a landing-site-prep robot gets dropped first. But that sounded like a lot of hovering to me, and a solution that would be very specific to lunar landing. I can't see that being successful on anything with higher gravity.
Better perhaps to send a separate stage or a scouting mission to do the work, then land later.
... and then Apollo 12 targeted one of the earlier Surveyor probes (which had successfully done its own automated moon landing in the mid-1960s!), and the guidance system had it coming down very close to the earlier probe -- astronaut Pete Conrad manually overrode it to make sure they stayed a safe distance away.
There had been upgrades to software and procedures since Apollo 11 -- most notably, a new guidance parameter the astronauts could enter ("noun 69") to correct for deviations between the planned lunar orbit and the one in which the spacecraft actually was, before descent.
Fair enough; Apollo 12 landed within walking distance of the Surveyor probe, but I don't have enough information to know whether 535 feet from the probe was exactly on target, or hundreds of feet off target. So maybe we could have landed on a pad 50 years ago, too?
Apollo 11/Eagle was deliberately piloted away from the initial landing site because the pilot did not think the original location was safe. So until a perfectly placed target for a robot to land on like SpaceX does (which seems only likely if establishing a sort of base), the robots will need to be made smarter about landing or built to be more agile on landing on less than ideal sites.
A launch and return to the same rotating body is surely a simpler maneuver than orbital transfer to a different spinning body and landing. No doubt we are better at it but I’m not sure earth landings are an accurate analog.
That depends on how much atmosphere. Mars has enough atmosphere to be annoying, but not really enough to be useful. Winds can throw you off target, but you can't use a parachute for a soft landing.
The article mentions that SpaceX has landed on the moon once, and tipped over. The moon is harder to land on then the Earth - less gravity and atmosphere.
SpaceX launched Odysseus. If you want to argue that this doesn't count as SpaceX landing, that's fine, but then it's even less evidence of Spacex's ability to land anything on the moon standing up.
The landing and take off tanks would have to be ballast tanks I suspect. Meaning at the bottom, center of the craft, where the moment arm is the most favorable.
If Flight 3 explodes again, my completely armchair prediction is that stage 1 will get something similar, but to stop sloshing on boostback.
That sideways drift was the bane of my existence. I could never quite kill all of my horizontal velocity, and tipping over was common. (Just as the article said)
I wonder how SpaceX will solve this reliably for Starship?
Yeah, I can't remember the show, but it was some time travel thing, and one of the tech guys isn't as excited as everyone else at the prospect of visiting great moments in history. They ask him why, and he says, "well, I'm black, so...."
There's probably several different shows that match this description, but you're probably thinking of Star Trek DS9, Season 6, Episode 13, "Far Beyond the Stars".
I wouldn't want to give up my toys. I don't have enough brain cells left to accommodate to 1960s style programming, let alone the outward appearance needed to convince someone to let me use their mainframe back then.
When I was a kid I used my bike to flawlessly get around everywhere I wanted to go.
At some point I wanted to go to places or in an amount of time or with cargo that a bike wouldn't allow.
The Artemis program is doing something similar but not the same as Apollo. It's different so it requires a change in the architecture which in turn means a series of problems because change is hard. Which truthfully is the exact same thing Apollo went through. Apollo was only six for six if you ignore everything that went before it. If you look the events before Apollo 11 it's easy to see that there were difficulties.
In this vein I've always thought it would be cool to see what kind of sports we could have in a zero gravity stadium in orbit. Something like the training facilities in Ender's game.
Maybe a sport like Quidditch could become a reality
they could have tossed something at least, somehow they managed to do all that footage without anything I can use to combat the conspiracy theorists who just say the footage is slowed down
What you do is descend very slowly, as you descend your thrusters will slowly melt a smooth landing pad beneath you. The only problem is you have to sacrifice part of the landing legs when you take off because obviously the melted cheese will bind to them once you touch down.
There is this experiment in OpenAI Gym to land a spacecraft via reinforcement learning. Is reinforcement learning actually working for this, and are such models deployed to real rockets, instead of "hardcoded" math?
Reinforcement learning does work for this, but it's brittle. You almost always end up with a strategy that exploits inaccuracies in the physics simulation – from the perspective of the RL algorithm, useful quirks of the laws of physics – and so doesn't transfer to reality very well, if at all. Its behaviour outside the conditions observed in training is not guaranteed (or even expected) to be sensible, and even its behaviour within the training conditions is often hard to characterise.
An algorithm designed by people who know what they're doing is usually better. More effort, yes, but rockets are a lot of effort! We can afford to pay the cost for a reliable landing system.
If you go fast enough sideways, the lander goes off screen and you can fall past the ground. Then you can flip for unlimited reward. Unfortunately, you can't then crash to see a final score!
"Why is there a sudden epidemic of spacecraft rolling on the moon like Olympic gymnasts performing floor routines?"
That's not how statistics work. We don't have a "sudden epidemic", we just happened to get unlucky a few times in a short period.
The exact same underlying risks and chances of success could have led to a long period of everything working fine, or (the least likely outcome) a perfectly spaced series of accidents occurring at whatever the mean rate is.
Not understanding this is part of how we let people get away with lax safety standards. Nothing gets mass attention until enough people get unlucky in a short period, despite the safety standards being lax the whole time. (I think many people reading this could name a company this has happened to recently -- but will attention stay on them for long when random chance gives us a period of no problems?)
I couldn't find the relevant XKCD but I remember one along the lines of "why did they just do Y?". I say all of this in jest, as this is what we do here at HN: give our opinion on areas outside our expertise.
I'm all for the US space program returning to the Moon and the NASA public-private approach seems fairly reasonable.
It is very odd however to see no mention of the fact that China is about a decade ahead, having completed the Chang'e 3, 4 and 5 missions. which included a successful return of Moon rocks to the Earth. Two more missions are in the works.
The article mentions a Japanese effort, but the omission of China's successes seems fairly deliberate. I wonder what the motivation was?
The aviators might say - a good landing is one you walk away from.
How exactly do you define a successful landing? What if you're upright but all four legs collapsed and the spacecraft crushed your primary science payload?
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