CEV Announcement

Henry Spencer wrote:
In article .com,
Tom Cuddihy wrote:
...if you do other than nose-first docking you're now loking at a
bigger heatsheild and thus a bigger vehicle because the heat shield has
to protect the docking mechanism...

Bear in mind that bigger doesn't necessarily mean heavier. Heatshield
mass scales very strongly with the *mass* of the capsule, but almost not
at all with its *size*. If you need a capsule with enough room inside for
a docking assembly, it's no big deal, if you can restrain yourself from
filling any further empty space with more equipment.

ha. you put that caveat in there for a reason...you obviously have
observed NASA at work before... ;-)

The only real limitation is that a capsule substantially bigger than the
top diameter of the launcher is a headache. (A *little* bigger is fine;
"hammerhead" payload fairings, mildly wider than the launcher top, are
common.)

By the way, *why* does the docking mechanism have to go inside the
heatshield? TKS's didn't. For that matter, Soyuz's doesn't (it's on
the orbital module, not the reentry module).

Yes, it's certainly technically feasible, but post Columbia about as
likely as building a technically feasible new reactor at Three Mile
Island. The technically possible bears little resemblance to the
politically feasible when it comes to government. It would take an
enormous investment of NASA's time to change public perceptions about
reentry heatshields.


which if it's going to fit people
through comfortably, and probably at a minimum in a spacesuit, requires
at least a meter wide hatch.

What *have* you been drinking? The Apollo CM/LM tunnel was about 75cm in
diameter, and was passable to a suited astronaut (as witness Dave Scott's
stand-up EVA in the LM docking hatch on Apollo 15).

that 75 inch hatch was only passable to a suited astronaut because he
was not wearing the suit backpack--Dave Scott was wearing a spacesuit
directly plugged into the LM via hoses. If he'd been wearing the
backpack, no such EVA would have been possible, the suit+backpack
couldn't have fit though the circular hole.
In addition, if lunar gravity hadn't been holding him perpendicular to
the hatch and he hadn't been standing on a ladder, it probably would
have been a lot more problematic. Gravity solves a lot of problems.

either way, NASA's not going to allow a hatch that doesn't allow
astronaut entry without taking off the lifesupport backpack.


Can you design such a thing as a small, multi-port docking adapter? Now
you're talking about lofting a Unity node along with the CEV.

Hardly. The ASTP docking module -- only two ports, but with a *lot* more
equipment than you'd need for this -- weighed only 2t fully loaded.

ok, it might be doable but it does add significant mass to the overall
vehicle.

There seems to be an institutional terror of orbital assembly
at NASA, but as the other Henry points out, they'll need to
do it sooner or later, so it might as well be sooner...

Why will NASA need to do it sooner or later?

Because we're not talking about a one-shot program here. The missions
will get bigger. They will outgrow *any* fixed-size launcher eventually;
the only question is when. Either you keep developing newer and bigger
launchers every few years -- which is very expensive, since you don't
really recover your investment on launcher N before starting on N+1 -- or
you start using orbital assembly at some point. And once you concede that
*eventually* you will need orbital assembly, it becomes clear that the
sooner you start, the better.

golly, we started pretty early with ISS. Is that what you mean?

Note that even Apollo used orbital assembly, in a small way. Why the
paranoid fear of it?

even a 30 ton CEV would require earth orbit rdv with the lunar transfer
stage.

that 75 inch hatch was only passable to a suited astronaut because he
was not wearing the suit backpack--Dave Scott was wearing a spacesuit
directly plugged into the LM via hoses. If he'd been wearing the
backpack, no such EVA would have been possible

75 cm, not inches.

Tom Cuddihy wrote:
Henry Spencer wrote:
In article .com,
Tom Cuddihy wrote:
...if you do other than nose-first docking you're now loking at a
bigger heatsheild and thus a bigger vehicle because the heat shield has
to protect the docking mechanism...

Bear in mind that bigger doesn't necessarily mean heavier. Heatshield
mass scales very strongly with the *mass* of the capsule, but almost not
at all with its *size*. If you need a capsule with enough room inside for
a docking assembly, it's no big deal, if you can restrain yourself from
filling any further empty space with more equipment.

ha. you put that caveat in there for a reason...you obviously have
observed NASA at work before... ;-)

The only real limitation is that a capsule substantially bigger than the
top diameter of the launcher is a headache. (A *little* bigger is fine;
"hammerhead" payload fairings, mildly wider than the launcher top, are
common.)

By the way, *why* does the docking mechanism have to go inside the
heatshield? TKS's didn't. For that matter, Soyuz's doesn't (it's on
the orbital module, not the reentry module).

Yes, it's certainly technically feasible, but post Columbia about as
likely as building a technically feasible new reactor at Three Mile
Island. The technically possible bears little resemblance to the
politically feasible when it comes to government. It would take an
enormous investment of NASA's time to change public perceptions about
reentry heatshields.


or the puplic confedence in any reentry system for that matter, but
what is interesting is that the Progress "splashed down " with over a
ton of cargo, what would stop a cargo carrier (unmaned) from having a
heatshield ?


which if it's going to fit people
through comfortably, and probably at a minimum in a spacesuit, requires
at least a meter wide hatch.

What *have* you been drinking? The Apollo CM/LM tunnel was about 75cm in
diameter, and was passable to a suited astronaut (as witness Dave Scott's
stand-up EVA in the LM docking hatch on Apollo 15).

that 75 inch hatch was only passable to a suited astronaut because he
was not wearing the suit backpack--Dave Scott was wearing a spacesuit
directly plugged into the LM via hoses. If he'd been wearing the
backpack, no such EVA would have been possible, the suit+backpack
couldn't have fit though the circular hole.
In addition, if lunar gravity hadn't been holding him perpendicular to
the hatch and he hadn't been standing on a ladder, it probably would
have been a lot more problematic. Gravity solves a lot of problems.

either way, NASA's not going to allow a hatch that doesn't allow
astronaut entry without taking off the lifesupport backpack.

the gemini b was equiped with ejection seats, and the hatches for
those opened out, like the fix for the apollo command capsule, but
there wouldn't be enough room sit in the seat with the support pack on,
so they wouldn't be wearing one.


Can you design such a thing as a small, multi-port docking adapter? Now
you're talking about lofting a Unity node along with the CEV.

Hardly. The ASTP docking module -- only two ports, but with a *lot* more
equipment than you'd need for this -- weighed only 2t fully loaded.

ok, it might be doable but it does add significant mass to the overall
vehicle.

There seems to be an institutional terror of orbital assembly
at NASA, but as the other Henry points out, they'll need to
do it sooner or later, so it might as well be sooner...

Why will NASA need to do it sooner or later?

Because we're not talking about a one-shot program here. The missions
will get bigger. They will outgrow *any* fixed-size launcher eventually;
the only question is when. Either you keep developing newer and bigger
launchers every few years -- which is very expensive, since you don't
really recover your investment on launcher N before starting on N+1 -- or

that was one point in favor of the lighter capsule, you where not
dependent on any one launcher, the HL-10 concept was desighend with 2
ejection seats, the x-24 had a mass under 5,000 kg, was to have inconel
and BeOxide heat shields, something simular could also be used as a
lifeboat, that wasn't depenant on one launch system.

you start using orbital assembly at some point. And once you concede that
*eventually* you will need orbital assembly, it becomes clear that the
sooner you start, the better.

golly, we started pretty early with ISS. Is that what you mean?

Note that even Apollo used orbital assembly, in a small way. Why the
paranoid fear of it?

even a 30 ton CEV would require earth orbit rdv with the lunar transfer
stage.

"Henry Spencer" wrote in message
...
In article ,
Jeff Findley wrote:
...The Apollo CM/LM tunnel was about 75cm in
diameter, and was passable to a suited astronaut (as witness Dave
Scott's
stand-up EVA in the LM docking hatch on Apollo 15).

Interesting. I don't remember ever reading about this, but a quick web
search confirms that this was indeed done in order to take pictures of
the
site:

http://www.fukuoka-edu.ac.jp/~kanami...15.htm#standup

It was Scott's idea, based on the geology training: when you arrive at a
new site, the first thing you do is find a high spot and take a look
around. In addition to the photography, it let him pick out a good spot
for the ALSEP, and confirm that there wasn't going to be a problem with
driving in certain areas which had originally been considered doubtful.

From The Earth to the Moon shows all this.

I've wondered why later missions didn't also do this.


--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Henry Spencer wrote:

Su the Russian TKS -- qualified for manned flight but never flown
manned because its program got canceled -- had a pressurized service
module, reached via a heatshield hatch, with a docking assembly on the
rear. (TKS is gone, but its service module lives on: the Mir add-ons,
and the Zarya module which started ISS, were derivatives of it.)



I don't know if you'd call it a "service module" as such, it was
primarily meant to work in concert with the Almaz station, as a cargo
supply module and to provide added living space. In an unmanned mode it
could be used as a space tug, like the modified variant that delivered
the Kvant module to the Mir rear docking port.

Pat

Can you design such a thing as a small, multi-port docking adapter? Now
you're talking about lofting a Unity node along with the CEV.

Hardly. The ASTP docking module -- only two ports, but with a *lot* more
equipment than you'd need for this -- weighed only 2t fully loaded.


One thing that really surprised me when I was at Kennedy last month,
was the size of Unity. After walking through the full sized mock up,
I relised that it was a whole lot bigger than I originally though it
was

Kelly McDonald

Henry Vanderbilt writes:

Which eliminates the need to fly a six-man CEV with attendant new
larger-than-EELV-heavy booster every time you rotate Station crew.
(Might as well still be flying Shuttle; it'll end up costing about
as much per flight.)

Henry

I look at the current proposals and I wonder if they're designed to
make it seem that giving up shuttle will have been a bad idea.

pgf
--
Phil Fraering
Warning: I am very behind on usenet; if you really want me to
see a message, cc: me a copy. - pgf

Tom Cuddihy wrote:

IF you go with a standard capsule shape, that means the
docking mechanism is going to end up at the bow of the capsule,
as every 'docking' capsule so far launched has done. Have you
heard of a design that does not do a bow-forward docking?

The Soviet TKS/VA. Intended to be flown manned but only flown
unmanned.

Jim Davis

Henry Vanderbilt wrote:
Tom Cuddihy wrote:
Perhaps that's possible if you're willing to ignore the architecture of
the 'Constellation' program that's been put forward to this point, or
if you're willing to limit yourself to 4 people. I just don't see that
happening, and obviously now neither does Mike Griffen.


Ah, now we're wandering from "what's possible and makes sense" to
"what might Mike Griffin do given his constraints". I'm not trying
to guess what he might do yet - he's shown himself willing to deep-six
some of his constraints already. I'm just pointing out some of
the benefits of not assuming "the approach so far" is the only
possible way.

Sure, there's always another way to do things. But at some point you
have to make a decision *and stick to it* if you want to ever get a
project off the drawing board.

I'm no space historian, but I get the impression that NASA has made a
habit of starting on projects that could have been flying successfully
today if someone hadn't decided there might be a "better" option.

Henry Spencer wrote:

which if it's going to fit people
through comfortably, and probably at a minimum in a spacesuit, requires
at least a meter wide hatch.

What *have* you been drinking? The Apollo CM/LM tunnel was about 75cm in
diameter, and was passable to a suited astronaut (as witness Dave Scott's
stand-up EVA in the LM docking hatch on Apollo 15).

Perhaps NASA now has a representative recruitment policy - Astronauts
need to reflect today's population, not the population of 35 years ago.
So supersize that airlock!