Author Topic: Low Cost/Rapid Development Reusable LSAM  (Read 5768 times)

Offline 93143

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Re: Low Cost/Rapid Development Reusable LSAM
« Reply #20 on: 08/20/2010 06:04 PM »

The biggest issue here is that the "stacked" design (central engine, tanks around the engine, payload above) implies multiple H2 & O2 tanks, which makes your boiloff problem much worse.

Not necessarily: a 'toroidal common bulkhead' tank design could perhaps be used (although it would be more challenging to produce... on the other hand it could have several advantages over the multiple tanks approach on a 'traditional' lander, proper study would be required for specific mission requirements). Nevertheless, it would still be a challenge from the point of boil-off management if LH2 / LO2 would be the propellants.

If that's feasible, I can see how that would help the situation.

The obvious questions are how that would affect the dry mass and thermal properties of Altair.

However, I also believe one of the big issues with Altair is that the hot engine is embedded within the cold tanks. That would still be a problem, I presume.

If you're going with a fully-reusable stacked design, why not put the fuel tanks on top?  The lander would look like Mother Brain, but the centre of gravity on landing should actually be lower even with partly-full tanks; the only technical disadvantage that occurs to me is that the cryopropellant feedlines would be longer and traverse the vicinity of the crew compartment.

Unless you put the engines up on the base of the tank, and hung the payload and legs down from that, making surface access trivial...  maybe keep the engines further away from the dust...  but you'd need a big enough lander to justify at least three RL-10s, preferably four...  replace 'em with RL-60s and you have a Mars lander/ascender with surface refueling...  but this sounds like unnecessary duplication of load-bearing structure, with potentially large bending loads on the engine mounts; perhaps not such a good idea for an SSLA vehicle...  not to mention potential exhaust impingement on the landing gear...  On the other hand, I'm not so sure DTAL's two independent propulsion systems are such a great idea mass-wise either...

Hold on; the legs need to be fairly wide apart for the lower C of G to have any meaning.  I guess that qualifies as another technical disadvantage, unless you make the payload module pretty wide or the tank pretty tall...  or attach the legs to the base of the tank, in which case they'd be longer and heavier...
« Last Edit: 08/20/2010 06:08 PM by 93143 »

Offline kraisee

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Re: Low Cost/Rapid Development Reusable LSAM
« Reply #21 on: 08/20/2010 06:09 PM »
Fast Schedule.   Low Cost.   Increased Capability.

You can pick only two -- if you're lucky.

Ross.
« Last Edit: 08/20/2010 06:09 PM by kraisee »
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Offline Mr. Justice

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Re: Low Cost/Rapid Development Reusable LSAM
« Reply #22 on: 08/20/2010 06:48 PM »
I've posted another idea about a partially reusable LSAM based heavily on the DTAL. The decent module would almost be an ACES, while accent module would almost be the Orion SM it could really cut time and cost.
 
http://forum.nasaspaceflight.com/index.php?topic=19189.msg629184#msg629184
« Last Edit: 08/20/2010 06:49 PM by Mr. Justice »

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