The Apollo shape also increases the size of the main heat shield-which was half the weight of the command module. Soyuz, in discarding much of the spacecraft's habitable volume, reduces weight thereby. Not saying you're wrong; there are always trade-offs with design.
AH Challenge: Hermes flies
- Thread starter TheLoneAmigo
- Start date
The Apollo shape also increases the size of the main heat shield-which was half the weight of the command module. Soyuz, in discarding much of the spacecraft's habitable volume, reduces weight thereby. Not saying you're wrong; there are always trade-offs with design.
That has less to do with shape, just make sure that actual living space is not in the re-entry module. That is probably the single biggest weight saver. All the re-entry module needs to do is to provide a seat to each crew member, controls, & 2 days of life support. (and preferably also a heat shield
)That has less to do with shape, just make sure that actual living space is not in the re-entry module. That is probably the single biggest weight saver. All the re-entry module needs to do is to provide a seat to each crew member, controls, & 2 days of life support. (and preferably also a heat shield
Oh, certainly. It almost looks like the Soyuz beehive was chosen to most efficiently use the volume inside the payload shroud. An Apollo-style cone is most suited to a position on top, in which case your best bet is to put the orbital module underneath and have the spacecraft turn around and dock with it after reaching orbit, as with the lunar module. Of course then you'd have to put a docking system on the orbital module, increasing weight...
Then again you have the Vostok, which was a sphere weighted at one side-so the cosmonaut had a chance to survive an entirely unpowered reentry. Lots of useful choices.
TKS had a hatch in the heat shield, not sure how well that would have worked if they ever would have done a manned flight with it.
So did Blue Gemini. I think it would work if done right, but everyone would be reluctant to try it. On the other hand, if you're bold enough to fly Voskhod...
No, a standard Soyuz's heatshield was less massive because it wasn't designed for lunar-velocity entry, which has twice the heat flux of a LEO entry. Even for Lunar Zond, they had to both use a skip-entry to burn off speed first, and add a much larger heatshield. Plus, to duplicate the 0.3 hypersonic Lift/Drag of Apollo, Zond would have needed even more heatshield mass. So, the Soyuz design really isn't optimal for mass. Which is, incidentally, why all successful Mars entry vehicles have used an Apollo shape.
The actual advantage of the Soyuz shape is actually monostability: it's only stable in the correct direction for reentry. Apollo, due to its CoG being too far towards the nose, was also (slightly) stable in the nose-first direction. This monostability has saved a few Soyuzes that failed to separate from the SM correctly. On the other hand, Apollo never had a problem with separation, as that's one system that has lots of heritage from satellites.
So, it's not an accident that nearly all the proposed/in-development capsules today (e.g. Orion, Dragon, CST-100, European ACRV, and Russian PPTS) all have conical shapes with 60-70 degrees slopes. Indeed, the original ESAS document describing CEV (which became Orion) has pretty good discussion of the topic:
http://www.nasa.gov/pdf/140636main_ESAS_05.pdf
1) the Apollo capsule had to withstand escape-velocity speeds (close enough) because it was returning from the moon. Any merely earth orbital capsule has about half the heat problem to deal with.That has less to do with shape, just make sure that actual living space is not in the re-entry module. That is probably the single biggest weight saver. All the re-entry module needs to do is to provide a seat to each crew member, controls, & 2 days of life support. (and preferably also a heat shield
2) throwing away the living space means dropping that amount of reusability. Obviously Apollo capsules weren't reused, but Hermes or any of its capsule alternatives would have wanted to be.
Any attempt at reusability to date has ended up costing more than throw-aways (and, except for the space shuttle, being cancelled)... I also don't think a late-eighties capsule would try much reusability.
Archibald
Banned
General consensus is that Soyuz is really much lighter because it stages (like a rocket, it has multiple stages, making it more efficient).
Unfortunately the more number of *stages*the more risk of seperation events going wrong.
Soyuz 5 had a very, very scary reentry because a module did not separated in time.
Soyuz 5 flaming return by James Oberg.
Unfortunately the more number of *stages*the more risk of seperation events going wrong.
Soyuz 5 had a very, very scary reentry because a module did not separated in time.
Soyuz 5 flaming return by James Oberg.