Quote from: simcosmos on 08/12/2010 02:36 pmQuote from: MP99 on 08/12/2010 07:58 amThe 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.
Quote from: MP99 on 08/12/2010 07:58 amThe 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.
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.