CEV history

Brian Thorn wrote:
On Sun, 05 Feb 2006 07:45:49 -0600, Pat Flannery
wrote:

Mark Wade has added information to his Encyclopedia Astronautica website
about the history and contenders for the CEV design:
http://www.astronautix.com/craftfam/cev.htm
The final Lockheed design looked like a Soyuz A:
http://www.astronautix.com/graphics/z/zcevlocm.jpg
http://www.astronautix.com/craft/soyuza.htm

Another EA opportunity to dump on the US, I see. Has Wade ever made a
positive comment about NASA?

Why he's fixating on the "superiority" of Soyuz's three-module
arrangement (again) is baffling.

He's made the careless mistake of comparing the Earth-orbit Soyuz and
the lunar orbit CM. If you ignore the different roles, the Soyuz looks
lighter and roomier.

But the Lunar orbit version of the Soyuz was a two-seater, and the crew
compartments weighed more per seat than the CM and had additional
failure modes.

Note that on Boeing's Soyuz-style design, the orbital and entry modules
are more massive and complicated than the unitary design actually
selected.

Will

"Rand Simberg" wrote in message
...

Yes, the current architecture (and CEV design) assumes that people
returning from the moon will always return all the way to earth. Get
rid of this requirement (for instance, by developing routine
transportation to/from LEO) and now someone on a lunar excursion would
return instead to LEO, and there would be no need for a capsule with
big heat shield.

Aerobraking and/or propulsive entry into LEO from the trans-lunar
trajectory?

Jeff
--
Remove icky phrase from email address to get a valid address.

Henry Spencer wrote:
In article .com,
Will McLean wrote:
...Sure, you could eventually evolve it
into something useful, but at that point there would be nothing of the
original CEV architecture left...

The CEV, however, could be used essentially as is in the mission
profile I described.

Yes, but your mission profile is still very much like the existing one.
It's not clear that we are well-served by anything like that profile. For
example, if not just the lander but also the Earth-Moon transport becomes
reusable -- perhaps with a high-performance lander based in LEO, perhaps
with an inter-orbit transport based in LEO and a lander based in lunar
orbit -- then there is no role left for an Apollo-style capsule at all.


That's a lot of perhaps. (And assumes something other than the capsule
to get from Earth to to LEO)

And not all of these scenarios dispense with the capsule. It might be
most economical to recover your EDS stage by multi-pass aerocapture,
but you wouldn't want to subject your crew to that.


Even if you stick with an expendable lander, as payload to the surface
increases and stay times get longer, leaving part of the hardware in orbit
imposes more and more penalties.

Can you be more specific? If you are building a robust surface base,
the need for anytime return decreases: if someone has apendicitis, you
treat him in sick bay rather than sending him on a week long space
voyage home. And space seems like a more benign place than the lunar
surface, being beaten up by the long day-night cycle.


Eventually you start wanting to build a
lightweight return vehicle -- the lighter, the better -- which is taken
down to the surface. Here you still have an Apollo-style capsule with a
propulsion module under it, but it almost certainly can't be the big heavy
one being designed for CEV.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |


And what superfluous mass do you remove? If you can pare the mass
safely, why haven't you already done so?

(And now you start wanting an airlock on or in the capsule so you don't
track in as much dust. Which conflicts with the desire to make it as
light as possible.)



Will McLean

On Tue, 7 Feb 2006 18:30:03 GMT, in a place far, far away,
(Henry Spencer) made the phosphor on my monitor
glow in such a way as to indicate that:

In article .com,
Will McLean wrote:
...Sure, you could eventually evolve it
into something useful, but at that point there would be nothing of the
original CEV architecture left...

The CEV, however, could be used essentially as is in the mission
profile I described.

Yes, but your mission profile is still very much like the existing one.
It's not clear that we are well-served by anything like that profile. For
example, if not just the lander but also the Earth-Moon transport becomes
reusable -- perhaps with a high-performance lander based in LEO, perhaps
with an inter-orbit transport based in LEO and a lander based in lunar
orbit -- then there is no role left for an Apollo-style capsule at all.

Even if you stick with an expendable lander, as payload to the surface
increases and stay times get longer, leaving part of the hardware in orbit
imposes more and more penalties. Eventually you start wanting to build a
lightweight return vehicle -- the lighter, the better -- which is taken
down to the surface. Here you still have an Apollo-style capsule with a
propulsion module under it, but it almost certainly can't be the big heavy
one being designed for CEV.

Yes, the current architecture (and CEV design) assumes that people
returning from the moon will always return all the way to earth. Get
rid of this requirement (for instance, by developing routine
transportation to/from LEO) and now someone on a lunar excursion would
return instead to LEO, and there would be no need for a capsule with
big heat shield.

On 07 Feb 2006 07:59:55 -0500, Jim Kingdon wrote:

I really wasn't referring to the entire Constellation architecture,
but the CEV design (the Apollo-like spacecraft) itself. Aside from
being too heavy, I don't understand why so much hostility to it.

"Aside from being too heavy"....

Well, that's a pretty big one right there. Masses significantly more
than Apollo, doesn't do more than Apollo.

It's baseline crew of six versus Apollo's baseline three (Apollo was
capable of five, but only at significantly higher risk to the crew.)
It's baseline ground landing versus baseline water splashdown (Apollo
could do ground landing as well, but again, only at significantly
higher risk to the crew.) CEV's design goal is six months flight. We
don't know what Apollo could have been pushed to, but SL-3 showed it
ran into problems on long flights. CEV is intended for at least some
reusability, and this, I suspect, is where most of the extra mass is
going.

Brian

On Tue, 07 Feb 2006 22:52:03 GMT, h (Rand
Simberg) wrote:


Yes, the current architecture (and CEV design) assumes that people
returning from the moon will always return all the way to earth.

A fairly safe assumption.

Get
rid of this requirement (for instance, by developing routine
transportation to/from LEO) and now someone on a lunar excursion would
return instead to LEO, and there would be no need for a capsule with
big heat shield.

Then how do you get back into LEO? Aerobraking is still going to need
a big heat shield and/or heavy hulls for radiation protection.
Propulsive LEO entry is going to need much more mass than a big heat
shield, plus a bigger engine for TEI and LEOI, plus a bigger booster
for TLI.

Straight in seems far more economical, especially if the crew module
is reusable, as CEV is meant to be (with a new, bolt-on heat shield.)

Brian

Will McLean wrote:

The current design is launchable on the larger EELVs and Falcon 9 (if
it meets its payload goals).




Let's see Falcon 1 get airborne before we even begin discussing what a
Falcon 9 can do.

Pat

On Tue, 7 Feb 2006 15:03:12 -0500, in a place far, far away, "Jeff
Findley" made the phosphor on my monitor
glow in such a way as to indicate that:


"Rand Simberg" wrote in message
...

Yes, the current architecture (and CEV design) assumes that people
returning from the moon will always return all the way to earth. Get
rid of this requirement (for instance, by developing routine
transportation to/from LEO) and now someone on a lunar excursion would
return instead to LEO, and there would be no need for a capsule with
big heat shield.

Aerobraking and/or propulsive entry into LEO from the trans-lunar
trajectory?

Either or both, depending on the cost of propellant on the moon or at
EML1.

h (Rand Simberg) wrote in
:

On Tue, 07 Feb 2006 17:34:46 -0600, in a place far, far away, Brian
Thorn made the phosphor on my monitor glow in such
a way as to indicate that:

On Tue, 07 Feb 2006 22:52:03 GMT, h (Rand
Simberg) wrote:

Get
rid of this requirement (for instance, by developing routine
transportation to/from LEO) and now someone on a lunar excursion would
return instead to LEO, and there would be no need for a capsule with
big heat shield.

Then how do you get back into LEO? Aerobraking is still going to need
a big heat shield and/or heavy hulls for radiation protection.

Not as big as an entry heatshield. And it doesn't need the L/D. It's
a different design.

Scary. Aerocapture is sensitive to atmospheric conditions, and slight
errors in navigation or targeting could be fatal if you don't have an
"abort-to-surface" option. And the easiest way to do that is to size your
aerocapture heatshield for entry.

--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

On Tue, 07 Feb 2006 17:34:46 -0600, in a place far, far away, Brian
Thorn made the phosphor on my monitor glow in such
a way as to indicate that:

On Tue, 07 Feb 2006 22:52:03 GMT, h (Rand
Simberg) wrote:


Yes, the current architecture (and CEV design) assumes that people
returning from the moon will always return all the way to earth.

A fairly safe assumption.

Not for long, if private enterprise starts to get serious about LEO.

Get
rid of this requirement (for instance, by developing routine
transportation to/from LEO) and now someone on a lunar excursion would
return instead to LEO, and there would be no need for a capsule with
big heat shield.

Then how do you get back into LEO? Aerobraking is still going to need
a big heat shield and/or heavy hulls for radiation protection.

Not as big as an entry heatshield. And it doesn't need the L/D. It's
a different design.

Propulsive LEO entry is going to need much more mass than a big heat
shield, plus a bigger engine for TEI and LEOI, plus a bigger booster
for TLI.

Mass isn't the issue--cost is. And that depends on the cost of
propellants in various locations.

Straight in seems far more economical, especially if the crew module
is reusable, as CEV is meant to be (with a new, bolt-on heat shield.)

Under current infrastructure (and high cost of access) assumption,
yes. We need to change that, but instead, NASA is simply accepting
it, and building yet another unaffordable, unsustainable program.