Space-X Dragon

In article ,
Pat Flannery wrote:
(In fact, because of this Apollo had some glaring problems - like the
three axis gimbal system in the inertial measurement unit.)

I wonder if they'll use laser ring gyros on the new one?

Probably not -- those are now yesterday's technology. (For one thing,
despite what you might think, they still have moving parts.) Fiber-optic
gyros are increasingly replacing them, and hemispherical-resonator gyros
are another major competitor.

Also, it's no longer necessary to push the gyro technology hard, because
automatic star trackers can provide almost continuous attitude updating.
(Compare to Apollo, which got updates only every few hours when the crew
did a manual star sighting.)

For at least earth orbit, they should be able to update their navigation
computers via GPS.

With smart signal processing, you can get some limited use of GPS up to
much higher altitudes. Not the sort of essentially-instantaneous full
position solution that you get on the surface or in LEO, but data that
puts constraints on position and can be used, over time, to correct for
drift in on-board estimates. Might not be practical out at lunar
distances, though.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

In article . com,
Alex Terrell wrote:
With support for 7 passengers, if it docked with a service module
providing extra life support and space, could it take the crew of 7 to
lunar orbit? Or would it need an enhanced reentry shield?

Almost certainly it would need a heavier heatshield, although that needn't
be a big deal. Depending on how it does things like attitude sensing and
navigation, it might need other modest design changes for operation at
high altitude.

And of course, over and above the sort of service module you mention, it
would need a lot more propulsion.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

Henry Spencer wrote:
In article ,
Pat Flannery wrote:


Certainly, weight creep has been a big problem a Lockheed, dooming the
X-33, and causing severe problems with the JSF that endanger its S/VTOL
capabilities in the Marine version.


It's almost ubiquitous in aviation and spaceflight, but to varying
degrees. Only very rarely do you find a chief designer with the skill and
the stubbornness needed to unconditionally hold the line on mass; if there
weren't one or two historical examples, you might doubt whether it was
even possible.

I'm guessing the A4 in aviation. Is there a space example of ruthlessly
holding the line on mass?

--
Posted via a free Usenet account from http://www.teranews.com

On 12 Feb, 13:57, John Schilling wrote:
On 10 Feb 2007 23:57:33 -0800, "Alex Terrell"
wrote:

On 11 Feb, 06:46, "Jonathan Goff" wrote:
Henry,
Escape rockets can be placed underneath; there's no law of nature that
says they have to be on top.
And as you have pointed out previously, there are several laws of
nature that strongly suggest putting them on the bottom.
Though getting rid of them after they've served their purpose is
slightly more difficult.

Who says their only purpose is escape?

Any manned spacecraft that *doesn't* suffer a critical failure during
launch, is going to require additional propulsion for e.g. circularization
and eventual deorbit. The delta-V requirements for these are comparable
to the delta-V requirements for launch escape, and there's no reason you
can't use the same propulsion system for both.

That's true, though the requirements are very different. An escape
system needs to pull quite a few g, which may not be desirable in an
Orbital Maneuvering Engine.

"Derek Lyons" wrote in message
...
"Greg D. Moore \(Strider\)" wrote:

It's not just the capabilities. Much of what you say IS true. However
there's also a lot of "oral history" that is often lost. "Why did you put
that switch THERE?" "Oh we found that in simulations they'd hit it with
the
shoulder in the place we normally tried." Lots of little things that can
make a difference between an ok design and a great design.

When designing a new capsule, you find out where not to put switches
when you run the simulations for the new capsule. (I.E. that
particular bit of information is virtually useless unless the cabin is
pretty much the same.)

Right until you try that same thing in orbit, etc.

Point is there still a lot of "oral" history that can get lost when you only
design something once every decade or so.



Not to mention the fact - it's not obvious that we are losing all that
much. It's not as if we have a vast and deep well of knowledge... We
built three very different capsule designs, the first informing the
design of the second, and the third being largely an independent
creation. All acknowledged as great designs - and only one being
built on an existing (and quite shallow) experience base.


Agreed. There's not much, but there's definitely some.

I think the next decade will be better as more commercial companies start to
design new craft.

Some will be great, some will fail. But the state of the art will advance.

I'm interested in seeing what Scaled Composites comes up with for SS3 (if
ever).



D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

On Sun, 11 Feb 2007 21:46:23 +0100, "Guy Fawkes"
wrote:


"Henry Spencer" schreef in bericht
...
In article ,
Guy Fawkes wrote:
It's nice to have some computer generated pictures and list some nice
features, it's something entirely different to build a working spacecraft.
NASA is trying to do the latter.

Yes, and lately they haven't done too well at it -- their history in that
area has been an unbroken string of failures and canceled projects. These
days, they too specialize in computer-generated pictures and lists of nice
features. It's not clear that they *know* how to build working spacecraft
any more -- the guys who built Saturn and Apollo, and even the shuttle,
are gone now.

No faith in the capabillities of today's engineers? I think you'll find that
they're just as capable as the ones who built Apollo and Saturn, if not more
so. And thanks to today's computer technology they'll be able to build
better designs, quicker and cheaper in less time and they'll have been
tested and simulated far more streneously than the ones in the Apollo days.

However, spaceships are not built by giving engineers a pile of money and
saying, "go build a spaceship".

They are built by giving *institutions* a big pile of money and saying,
"go build a spaceship". Institutions which are staffed primarily by
people who are not engineers, and which have internal dynamics that are
as important as the individual talents of the members.

There is sound reason to believe that NASA, as an institution, is no
longer capable of building a spaceship, *even if* it were somehow staffed
with every Apollo/Saturn engineer in their prime. And the same is true
of LockMart and BoeDonnel.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
*661-718-0955 or 661-275-6795 * -58th Rule of Acquisition *

Henry Spencer wrote:
The single thing that most concerns me about the White Cane (aka Stick) is
its lack of performance margins. Apollo succeeded, in large part, because
Wernher von Braun quietly set the specs for the Saturn V considerably
higher than Houston's official mass estimates for the Apollo spacecraft.


That shows the caliber of his team's engineering skill; they knew
nothing ever comes out as light as it looks on paper so build in a very
healthy reserve factor right from the beginning. Any excess capability
becomes gravy in the finished program, as was done with the J series
Apollo missions.
The Soviets never did get that fixed in regard to their N1/L3 program.
The N1 and L3 both came in overweight, and even if they had gotten the
N1 to work as planned, they were finding it just about impossible to
shave enough weight off the L3 for their original plan to work.

Pat

Chris Hall wrote:

I'm guessing the A4 in aviation. Is there a space example of
ruthlessly holding the line on mass?

I would think the Mercury capsule would be a case in point. You really
didn't have much choice but to do that because of the limited lifting
capabilities of the Atlas. It's either going to come in on-target for
mass, or it's not going to make it into orbit.
The early Discover/Corona program would be another possible example, due
to the limited lifting capability of the original Thor/Agena system in
its unaugmented form.
In some respects the Soviets were spoiled be their big, primative,
heavy, and very capable R-7.
Particularly once the Luna/Vostok and Molniya/Voskhod upper stages were
introduced, they could get fairly overweight in the payloads and still
have enough lifting power reserve to get them to orbit. It wasn't till
Soyuz came along that they really had to start watching every pound.
That laid-back approach to weight control really came back to bite them
in regard to the N1, which came in way overweight from what was planned.

Pat

In sci.space.policy message
roups.com, Mon, 12 Feb 2007 14:50:48, Alex Terrell
posted:
On 12 Feb, 13:57, John Schilling wrote:

Any manned spacecraft that *doesn't* suffer a critical failure during
launch, is going to require additional propulsion for e.g. circularization
and eventual deorbit. The delta-V requirements for these are comparable
to the delta-V requirements for launch escape, and there's no reason you
can't use the same propulsion system for both.

That's true, though the requirements are very different. An escape
system needs to pull quite a few g, which may not be desirable in an
Orbital Maneuvering Engine.

Two obvious classes of solution for that :

(1) [expressed in Apollo terms] Put the rockets on the capsule. For
escape, they give the capsule several gee; for propulsion to orbit. they
give (capsule + service module) a substantially lower acceleration.

(2) Use a dozen or more rocket units. For propulsion, fire in opposite
pairs; for escape, fire them all at once. Choose number and rating
accordingly.

--
(c) John Stockton, Surrey, UK. Turnpike v6.05 MIME.
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

On 13 Feb, 15:52, Dr J R Stockton
wrote:
In sci.space.policy message
roups.com, Mon, 12 Feb 2007 14:50:48, Alex Terrell
posted:

On 12 Feb, 13:57, John Schilling wrote:
Any manned spacecraft that *doesn't* suffer a critical failure during
launch, is going to require additional propulsion for e.g. circularization
and eventual deorbit. The delta-V requirements for these are comparable
to the delta-V requirements for launch escape, and there's no reason you
can't use the same propulsion system for both.

That's true, though the requirements are very different. An escape
system needs to pull quite a few g, which may not be desirable in an
Orbital Maneuvering Engine.

Two obvious classes of solution for that :

(1) [expressed in Apollo terms] Put the rockets on the capsule. For
escape, they give the capsule several gee; for propulsion to orbit. they
give (capsule + service module) a substantially lower acceleration.

(2) Use a dozen or more rocket units. For propulsion, fire in opposite
pairs; for escape, fire them all at once. Choose number and rating
accordingly.

Thanks. I see this is covered under the topic "Space Shuttle
Replacement". Taking the liberty of posting Henry's quote:

HS: Yep, one propulsion system for launch escape, maneuvering, and
landing.
HS: The engineering of that looks a little challenging to me -- those
engines
HS: have to cover quite a range of requirements -- but it's a good
idea if you
HS: can make the numbers work.

For an almost blank sheet design like Dragon or Orion, this would seem
a sensible approach. I doubt in these case it would make sense to land
the engine, but certainly escape and maneuver.