Patchouli - 30/3/2008 9:40 PM
MTV acting as a breaking stage
which it isn't. The CEV will detach days before reaching earth
Patchouli - 30/3/2008 9:40 PM
Lifting bodies can perform lunar reentries and in theory so can a space plane if a skip reentry is used.
The Apollo is not the only shape one can use for this nor is it the best LM likely hit on the best shape so far with their first CEV concept the lifting CEV.
The apollo shape can't be used for high speed mars returns with out the MTV acting as a breaking stage or a skip reentry is used for example while a lifting body can perform a direct return.
Lockheed Martin found they needed a L/D of at least 1 if the G forces were to be kept under 6 or 7.
The LM vehicle was designed with mars return in mind and they went and figured out how to apply it for lunar missions.
Other workable shapes the soyuz headlamp shape not as low g as apollo but within limits as well as the biconic shape.
The biconic shape might be more ideal as this also might work for mars reentry and provides lots of cross range yet is still very simple it's also more mass efficient then apollo.
Here's a link of a biconic vehicle showing how the interior space is better utilized.
http://images.spaceref.com/news/2005/biconic.cev.l.jpg
As far as mass goes the three module soyuz system is by far the most mass efficient system tried so far and this is what the Chinese choose likely with the moon in mind.
Though having three modules can be used with any shape of reentry vehicle if you move the parts around.
The LM CEV concept for example did use three modules for lunar trips even though it was a lifting body.
All conjecture without any facts
Hmm, I think there are some strong connections between L/D and re-entry gees anyway.
This getting to be thread hijack but as far as the MTV goes well we all have no firm idea as there is no mars transport system finalized yet.
A mars mission is very far off so everything is nothing more then speculation and theory.
Even if Griffin says something on what will be used there will have been several Presidents and NASA administrators by then.
It's just too early to be set on anything at this moment in time esp when things like radiation shielding crew size needed and amount of artificial g required is not known.
Though on G it's likely best to error on the side of being conservative.
It would be bad PR to have to crew end up wheelchair bound or even unable to return to earth.
We don't even have formal funding set aside at this moment for R&D on the propulsion for the mission as that has not been decided yet.
The final form may not be realized until someone finds out whither there is ice on the moon to mined and is it economical when compared to alternatives.
NEP might win out just because it'll allow one to power a magnetic bubble since they found the radiation is to high to be safe.
The closest thing I saw to a detailed plan was a BTNR mission that made use of a transhab and the VASIMR study.
Oh and Zurbin's ISRU mission was fairly detailed engineering wise but didn't take some human physiology issues into account early on.
The Orion might not even be used on a mars mission the return vehicle could be something like Zurbin's ERV or could be something no one has even seen yet because it hasn't been invented yet.
By 2030 the Orion could be nothing more then a museum piece having been replaced by a new vehicle and hopefully it will be replaced by then.
We don't want to repeat the shuttle ad keep a vehicle around long after it becomes outdated.
Heck by 2030 HLVs as we know them may have fallen out of fashion to low cost RLVs and robotic assembly.
The biconic shape might be more ideal as this also might work for mars reentry and provides lots of cross range yet is still very simple it's also more mass efficient then apollo.
Er, no... even from that drawing you can see dead space everywhere.
Apollo capsule good. Apollo capsule works. We like Apollo capsule. Everybody like Apollo capsule.
Yes, 3 modules is more mass efficient but manned spacecraft are pricey and it is worth recycling much of them. Also, you don't have to worry about yet another separation event (which almost resulted in one lost Soyuz crew, I believe).
Patchouli - 1/4/2008 7:29 AM
1. Oh and Zurbin's ISRU mission was fairly detailed engineering wise but didn't take some human physiology issues into account early on.
2. By 2030 the Orion could be nothing more then a museum piece having been replaced by a new vehicle and hopefully it will be replaced by then.
1. I disagree, he baselined artificial gravity at very conservative RPM values and also suggested opposition-class trajectory for its lower g loadings on Earth re-entry - as opposed to the conjuction class "fast" trajectory favoured by NASA which would have resulted in plenty of Gs for the crew.
2. Yeah we can hope but past experience proves us wrong. If Orion enjoys the success of Soyuz, we could wave bye-bye to Orion by 2065. Kliper might hang around until 2070.
Even if you conjecture passenger-carrying RLVs by 2030, they are not suited for lunar or Mars missions which is what Kliper / ACTS and Orion are for.
Lampyridae - 31/3/2008 10:28 PM
The biconic shape might be more ideal as this also might work for mars reentry and provides lots of cross range yet is still very simple it's also more mass efficient then apollo.
Er, no... even from that drawing you can see dead space everywhere.
Apollo capsule good. Apollo capsule works. We like Apollo capsule. Everybody like Apollo capsule.
Yes, 3 modules is more mass efficient but manned spacecraft are pricey and it is worth recycling much of them. Also, you don't have to worry about yet another separation event (which almost resulted in one lost Soyuz crew, I believe).
Did result in loss of one Soyuz crew (Soyuz 11). The valve failure was caused by the orbital module separation.
Almost resulted in loss of two more (Soyuz 5, Soyuz TM-5). In the former, separation didn't happen when it should have; in the latter, separation almost happened when it shouldn't have.