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New lander concept

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1:51 am
January 12, 2010

Luke Maurits

Adelaide, Australia

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Post edited 7:51 am – January 12, 2010 by Luke Maurits

Here is a concept image for a new "pyramidal cage lander" I have been playing with in my mind. It's designed to easily dock directly on to the nose section of the CM via a nose module that stacks on for that purpose.

The use of three legs instead of four and of circular support beams rather than square ones is motivated by trying to save as much mass as possible in the frame. I'm picturing all the "beams" in this structure as circular aluminium tubing (less massive than square tubing). To eliminate the mass of a seat the astronaut either stands in the "cage" part at the top of the lander, with their feet on some footing support structure not shown here and their hands holding two of the side bars (in such a design the astronaut would of course be tightly tethered to the lander) or they are actually suspended in the cage by a harness with elastic links to the circular support beams. Sort of like a baby bouncer:

except with two sets of straps, one up and one down. In this way the astronaut's body doesn't actually have to accept any of the shock of a potentially rough landing – they'd just bounce around a lot. The lengths and elasticity of the straps would be such that in any reasonable landing scenario the astronaut's body would remain confined to the interior of the cage region without impacting the structure at all.

Unpictured are:

Three cold gas RCS units placed on the lower circular support beam, positioned inbetween the side beams, to allow rotation and attitude control.
A box of electronics on top of the tanks and engine and underneath the support that the astronaut would stand on if we didn't go with the baby bouncer idea.

The question arises of how an astronaut might control this thing if suspended by straps, and I'll admit I haven't fully thought this out. I think that with good navigation hardware, RCS and good software we could entirely automate the descent phase – once harnessed up the astronaut could press and hold two buttons integrated into the top straps (one in each strap) for five seconds to initiate the automated descent sequence (which would be tested unmanned in an earlier mission before an actual landing, of course). I'm not sure ascent could be made quite this easy, though.

I don't know how feasible this idea is but I thougth I'd throw it out there as an example of the sorts of out-of-the-box thinking we'll need to make this whole thing work with Falcon 9 mass or less, and to see what people thought.

Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.

10:54 pm
January 12, 2010

Luke Maurits

Adelaide, Australia

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posts 1483

Not a popular idea, or are you all just stunned into silence by its brilliance? :p

Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.

4:24 am
January 13, 2010

brmj

Rochester, New York, United States

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posts 402

I think this design might be a step in the right direction, but I don't think it is necessarily ready to be our final design. I have a few issues with it. One issue is that it has a smaller base and higher center of gravity than the other design, making it less tolerant of bad landings. Another concern is that the taller structure might add more mass than the seat would have. I'm not sure that's the case, but I'm just throwing that out there.

A few other things to consider for future designs or refinements: If we are using LOX/LH2 then we won't be able to have tanks of equal size. The larger amount of tanks we divide our fuel between, the more mass gets used in fuel tank walls. A wider base might be nice if it was feasible without adding to much junk mass in the form of legs and such.

I'm currently thinking off and on about a design built around a single rounded cylindrical tank with an internal bulkhead or a pair of stacked spherical tanks of the right diameter. This design would have an even higher center of gravity than yours, but would probably save quite a bit of tank mass. I'm trying to think of ways to minimize that problem.

Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)

4:36 am
January 13, 2010

Luke Maurits

Adelaide, Australia

Admin

posts 1483

brmj said:

I think this design might be a step in the right direction, but I don't think it is necessarily ready to be our final design.

Oh, it definitely isn't, and I didn't mean to propose it as such, it was just a concept. It will need to be refined significantly before we could even think of replacing the current design with it.

brmj said:

I have a few issues with it. One issue is that it has a smaller base and higher center of gravity than the other design, making it less tolerant of bad landings. Another concern is that the taller structure might add more mass than the seat would have. I'm not sure that's the case, but I'm just throwing that out there.

I will admit I haven't crunched the numbers to verify this, but I imagine that the mass of the frame would be so small compared to the hundreds of kilograms of propellant in the tanks that, even though this lander is a lot taller than the other one, the centre of gravity might have moved up by perhaps a few inches. It has ocurred to me that it may be more massive than the seat, if the reduced mass from the fewer legs and circular structure don't make up for this then I guess that's a shortcoming.

brmj said:

A few other things to consider for future designs or refinements: If we are using LOX/LH2 then we won't be able to have tanks of equal size. The larger amount of tanks we divide our fuel between, the more mass gets used in fuel tank walls. A wider base might be nice if it was feasible without adding to much junk mass in the form of legs and such.

Yeah, I was thinking about the tank size/shape issue too. I was hoping to come up with a solution whereby the descent and ascent fuel were held in separate tanks and the descent tanks could be left behind on the surface), but I couldn't think of a way to do it that didn't invovle the centre of mass shifting significantly, so I went with our old equal sized spheres approach, even though I concur that it will not work at all for LOX/H2 (with LOx/LCH4 they would be roughly equal, but there's no guarantee we'll be able to get things like enough to use it – mind you, I am starting to think this is not impossible, as discussed in the "fuel tanks for bravo" thread).

brmj said:

I'm currently thinking off and on about a design built around a single rounded cylindrical tank with an internal bulkhead or a pair of stacked spherical tanks of the right diameter. This design would have an even higher center of gravity than yours, but would probably save quite a bit of tank mass. I'm trying to think of ways to minimize that problem.

I really like the cylindrical tank with internal bulkhead idea, I think we should stick to it where we can. A vertical arrangement of tanks would let us discard empty ones without unbalancing the lander, so it is well worth pursuing. Let us know if you think of anything good.

Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.

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