Layover Lunar Lander

A lunar lander concept I haven’t seen elsewhere is a layover concept. A tall ship lands on its’ tail the way the several suborbital hoppers and the Falcon9 has been doing for several years now. After landing and checking the area to one side, a small thruster tips it over on two legs. Before reaching the surface, some landing rockets in the nose fire to bring velocity to zero as the nose lands on a couple more much smaller legs.

If the lander is 100 meters tall, the terminal velocity that must be braked before the nose landing is under 20 m/s. Stopping 100 tons just at the surface would require between 400 and 700 kg of propellant depending on the Isp in use. If feasible, seems like a fair trade off as opposed to raising and lowering people, supplies, and equipment 100 meters for the duration of the mission.

The lower legs on the pivot side would need to be able to handle loads from two directions, though the legs at the nose could be quite light. One alternative leg option is to have the lower pivoting legs articulate up under the body of the vehicle to split the loading better and to reduce braking thrust requirements a bit more.

The tip over landing should be quite simple as there would be no question of where the vehicle is in relation to the ground at any given time. Of course smaller vehicles would have even less trouble and use less propellant. A 20 meter high vehicle with a 10 ton payload would require only 20-30 kg of braking propellant.

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johnhare

johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
johnhare

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johnhare

About johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
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23 Responses to Layover Lunar Lander

  1. Matt says:

    Interesting idea. It would hinder reuse of the lander. Also the cargo and crew would be shaken, not stirred.

  2. johnhare johnhare says:

    Reuse would be a similar burn to stand the lander back up before lift off. Just reversing the sequence.

    I don’t see where the cargo and crew would be shaken. Small burn to tip and 1 Earth gee for a couple of seconds to zero velocity at horizontal. Lunar gee at 1/6 Earth gee switches a few intuitive concepts. I couldn’t see this as desirable for the F9 on the landing barges for instance.

  3. This concept has been discussed on and off at places like NSF. The main question I have is, how is this really different, much less better than DTAL? When you think about it, Starship already does a dual axis landing at Earth and Mars (or will, when it gets there). I think LSS is just a successful attempt to sell a minimally modified Starship to NASA (for a fraction the cost of competing designs). There’s no reason why it couldn’t descend to zero horizontal velocity, a few hundred meters up, switch on landing thrusters, switch off the main engines, and descend on its side to the surface. The main changes from the existing design would be distributing the dorsal thrusters to the ventral surface (some fore, some aft) and relocating the landing legs. Take off would be the reverse, just as with a convention ACES or Centaur based DTAL design. That said, I don’t see the elevator as a problem either. They’re going to need it for Mars. I’ll leave it up to you and others to figure out the stresses on a layover lander, but I believe they’d be much larger than on a DTAL design.

    I don’t know if my post on Transterrestrial Musings is the one you saw, but if it was, I meant well, and apply the idea to all prospce blogs and discussion groups. I think it’s time to drop the OldSpace thinking (unless its a concept that’s not invalidated by reusability, refueling, and large size) and move on. The example I had in mind was talking about fuel depots sized for refueling Centaur and ACES. A useful fuel depot for Starship is going to be the size of a ULCC class supertanker, holding hundreds of thousands of metric tons of fuel, able to fill up a couple of hundred Starships at a time. Are we really expecting that to happen? You’d look up and see something like an ocean liner passing overhead, visible in the daytime sky, I think. It’s worth talking about. Musk’s plan is to use a accumulation tanker for each Starship, where tankers would fill the AT, then that would fill the expeditionary vehicle. That’s all that’s needed for the next decade or so, but then what?

  4. Spike says:

    If the vehicle’s CG isn’t too high and the legs are long enough then you could do the entire pivot operation just using the legs, no engine required. An alternative would be flipping sideways shortly before touchdown and using two sets of small engines to land. In either case the side loads for this shouldn’t be any worse than Starship’s bellyflop, but I’d still be concerned if the vehicle is very tall/long.

    If this is intended to be a base supply vehicle then the weight budget for self-tipping should be considered against dedicated ground support equipment, either for tipping or a load/unload tower or crane. If it is a field lander then the landing engines as depicted are close to the ground, which can be a problem on the Moon. Neither concern is insurmountable.

    All-in-all an interesting concept for a direct Earth to Moon vehicle.

  5. johnhare johnhare says:

    William, I hadn’t seen this concept discussed before. Can you point me to a specific discussion? What specifically is DTAL?

    I believe the stresses on this would be considerably less than landing on the side. The vehicle would be stable going over all the way down due to the main legs being the pivot in continuous contact. Less unknowns, and less total thrust required as there would be no horizontal engines needed in the tail.

  6. otra jeff says:

    Why not for the F9 on barges or a landing pad? As a test of concept. Your experience with earth based construction places you in a better position to know than the engineers that cranes and ladders is expensive with time and prone to accidents. I hope someone will listen to you. Certainly by version 2.0 .

  7. johnhare johnhare says:

    otra Jeff, I don’t see the usefulness of this for the F9 landings. No cargo or crew to unload from high up. Also working in Earth gee and variable winds is a very different animal from Lunar gee and vacuum. Also, there are cranes and equipment of all types readily available here on Earth. Only if this were being considered for Lunar or other further destinations would I see doing a demonstrator.

    Jeff, thanks for the link. As I see it, the layover concept should be simpler, lighter, and more reliable than the DTAL. Of course there is some prejudice in my opinion and some level of trades should be done if someone were comparing the two ideas for actual use. As far as all the concepts other than the landing itself discussed in the paper, I don’t see why the layover concept couldn’t do the same.

  8. Spike says:

    @johnhare
    DTAL stands for “Dual Thrust Axis Landing”. Essentially the rocket descends vertically and then rotates to horizontal just before touchdown. ULA has a document describing the concept at https://www.ulalaunch.com/docs/default-source/exploration/dual-thrust-axis-lander-(dtal)-2009.pdf

  9. It’s stands for Dual Thrust-Axis Lander, and originally came from a ULA proposal. I stopped keeping track of NSF discussions after I received a lifetime ban in the wake of the 2009 Augustine Commission. My thoughts on the matter were deemed “horrendous,” and since the place was a horrendous time sink, I was glad to go.

    Here’s ULA’s original 2009 paper:

    https://www.ulalaunch.com/docs/default-source/exploration/dual-thrust-axis-lander-(dtal)-2009.pdf

    I suspect the biggest problem with the layover lander might be the bending moment. And bear in mind the current Lunar Starship design *already* has a ring of landing thrusters at the waist, so it’d simply be a matter of moving them all to what would then be the ventral side. The standard Starship is already built to withstand going through hypersonic entry and supersonic/subsonic descent to ground level on both Earth and Mars, followed by a sudden move to fully upright position for tail landing.

  10. johnhare John+hare says:

    Thanks all for sending me the link. I read the paper this morning

  11. Cameron G says:

    I’ve often wondered how it would trade to have the upper stage engines all in the belly (or side, depending on your perspective) instead of in the tail of a Starship type design.
    After staging, it rotates 90deg before ignition to point the engines the right way.
    Entry is possibly the hardest part, as the engines are exposed to entry heating unless some sort of moveable shield or something was fitted.
    Then the ‘bellyflop’ descent continues with no need to flip, just light the engines and land on it’s side. No sudden orientation changes, no sudden decrease in aerodynamic drag (less fuel to land), and everything ends up close to the ground.
    Launch loads would come in two different directions 90deg apart, but since we’re having a belly-first entry, those sort of forces are accounted for anyway?

  12. johnhare johnhare says:

    Cameron G,
    I’ve wondered about something similar with that whole thrust side being an aerospike nozzle/heatshield.

  13. Jeff Wright says:

    I can see the legs removed and used as A frames. Starship can then be outfitted as a wheeled mobile base. I might suggest power zip lines. Nuytco uses sub steel now declassified for dive suits.

  14. Spike says:

    @Cameron G
    Starship is short and thick compared to most rockets to help it slow down during the belly flop and it stages early to allow SuperHeavy to return to the pad. Turning sideways during ascent would be counter-productive at best due to increased wind resistance. It would also introduce structural issues since the belly flop is currently only performed when the rocket is almost out of fuel. This would also be a problem when trying to take off from Mars.

    A movable heat shield would add considerable weight and maintenance requirements and create a major point of failure to a life critical component. It would be far easier to put the engines on the opposite side from the heat shield and just roll over after reentry. This would require the payload to be able to handle acceleration from three directions instead of just two, and two of those would be opposite each other, but that is a comparatively minor problem.

    @johnhare
    Starship’s biggest advantage is in-orbit refueling so that it can act as its own third stage and aerospikes never compare well against dedicated vacuum engines in space. The only place that an aerospike has any advantage in the SS/SH stack is to replace the three landing engines on SS, but that would negate the savings from using common engines on both stages. Turning Starship sideways on ascent does nothing to help with that. I’m also not confident that they would hold up as heat shields since overheating is already problem for them.

    @Jeff Wright
    That might work for a smaller vehicle but I don’t think wheels would be practical for something as large as Starship, even on the moon. I’m not sure how zip lines or dive suits are relevant.

  15. Jardinero1 says:

    The paradigmatic flaw in every lander concept is that of carrying the landing rocket motor and the propellant, on the lander, every single time. The moon has one sixth the gravity and no atmosphere. Forget about carrying the rocket motor and the propellant, on the lander, every single time. Instead place the landing rocket, nozzle up, on the lunar surface. A lander can leave orbit and fall towards the landing rocket, which is now mounted on the lunar surface. As it approaches the landing area the landing rocket ignites, firing upward, at a plate, on the bottom of the lander. This slows the lander’s descent to the surface. For launch, you reverse the process. You can refuel the landing rocket via ISRU or literally drop propellant from orbit, in bulk cylinders, to the surface, and drag it to the landing site. Without a rocket, stuck to the bottom of the lander, your lander design can take on much more varied dimensions.

  16. johnhare john hare says:

    I was over halfway through your comment before realizing you were pulling one over. Thanks for the laugh.

  17. Jardinero1 says:

    Not at all.

    The landing rocket is not the conventional chemical rocket you might be imagining. The propellant could be small charges of explosive with a proximity fuse which are shot at the lander. The charges explode beneath the plate. The use of explosive charges for thrust is not a novel idea. Recall Project Orion, et al. I was also inspired by this.

    https://en.wikipedia.org/wiki/Laser_propulsion

    The problem with Laser Propulsion is that it requires considerable infrastructure on the lunar surface. My idea only requires an open plain on the surface, cannon, propellant and the crew, computer/hardware to operate it. The lander still requires chemical retro rocket for the deorbit burn. That can be placed on top of the lander with the lander rotated for the burn and then rotated back for landing.

    Again placing the propellant and landing rocket on the surface instead of the lander solves a lot of design problems. The lander can be scaled way up in size as well. It could be something as simple as a sled or pallet with the cargo and a crew vessel strapped on.

  18. Jardinero1 says:

    Not at all.

    The landing rocket is not the conventional chemical rocket you might be imagining. The propellant could be small charges of explosive with a proximity fuse which are shot at the lander. The charges explode beneath the plate. The use of explosive charges for thrust is not a novel idea. Recall Project Orion, et al. I was also inspired by this.

    https://en.wikipedia.org/wiki/Laser_propulsion

    The problem with Laser Propulsion is that it requires considerable infrastructure on the lunar surface. My idea only requires an open plain on the surface, cannon, propellant and the crew, computer/hardware to operate it. The lander still requires chemical retro rocket for the deorbit burn. That can be placed on top of the lander with the lander rotated for the burn and then rotated back for landing.

    Again placing the propellant and landing rocket on the surface instead of the lander solves a lot of design problems. The lander can be scaled way up in size as well. It could be something as simple as a sled or pallet with the cargo and a crew vessel strapped on.

  19. Jardinero1 says:

    Sorry about the double post of my comment. I thought it didn’t post the first time.

  20. johnhare johnhare says:

    You called it a rocket in the first comment, then describe a cannon in the second. Very different concepts. Also you might want to check out 7 November 2008 and 14 November 2008 in the archives. We discussed this concept at length with numbers. And found that another person had done a better job with the follow on concepts.

  21. Jardinero1 says:

    Sorry to irritate you. I thought this is a discussion thread and assumed we are allowed to reconsider and modify our thoughts. I read the comments you suggested. The difference between those comments and mine is that my comments address the singular problem of moving a lander from lunar orbit to the surface and then returning it to lunar orbit. My one overarching point is thus: if you remove the landing/ascent motor/rocket/stage and propellant from the lander and place it on the lunar surface; then many of your design problems with the lander are more readily resolved. As long as you have to stack crew and cargo atop the propellant and landing system then you are stuck with kludges to move same people and cargo from atop all that hardware down to the surface after landing.

  22. johnhare johnhare says:

    The thing is that you said rocket in the first comment and then described something that in no way resembles a rocket in your second. It is a discussion, just hopefully a coherent one. A rocket on the surface clearly won’t work as the exhaust attenuates far before it could interact properly with a spacecraft.

    The posts I suggested went over the concept in comments as well as work by others. There are ways to massively reduce the complexity and cost of a lunar vehicle. Airless aerobraking describes one way of getting them down. Launch cannon describes a way of sending them back up. The two together theoretically almost eliminate onboard propellant. I’m trying to understand what you are adding.

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