What advances have been made since Apollo?

On Sun, 07 Mar 2004 09:11:49 +0100, in a place far, far away, Robert
Kitzmüller made the phosphor on my
monitor glow in such a way as to indicate that:

I can also think of a lot of ways how to implement docking in orbit.
This does not mean that any of them are easy to implement, or cheap
either.
However you do it, it involves a huge number of components, which must
work together perfectly.

Well, they have to work well enough. I'm not sure that's the same as
"perfectly." You make it sound much more difficult than it is.

BTW: How are you going to do maintenence on the space tug? NASA has a
hard time to maintain the shuttles engines, on earth...

Shuttle engines are intrinsically hard to maintain, due to their
extremely high performance. There's no reason a space tug engine
would have to be such a finicky beast.

In article ,
Robert =?ISO-8859-1?Q?Kitzm=FCller?= wrote:
I can also think of a lot of ways how to implement docking in orbit.
This does not mean that any of them are easy to implement, or cheap
either.
However you do it, it involves a huge number of components, which must
work together perfectly.

No, just well enough. Apollo's docking system did not work perfectly, but
no mission was ever compromised by its foibles.

BTW: How are you going to do maintenence on the space tug? NASA has a
hard time to maintain the shuttles engines, on earth...

Rocket Science Fallacy #101 is the belief that the shuttle engines are
typical of rocket engines. They're not. DC-X's RL10s didn't need a
hundredth of that amount of maintenance to do a dozen flights and maybe
twice that many static tests.

How best to do maintenance, when the tug needs it -- which shouldn't be
all that often -- depends on the nature of the problem and also on the
size of the tug. Typically, the best thing to do would be to swap out the
affected module -- you'd build the tug modularized, to make this easy --
for a new one, and take the old one down to be fixed.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Robert Kitzmüller wrote in message ...
Christopher M. Jones wrote:
I can think of about a gazillion ways that this could be
done well.
[...]
Anywho, the amazing thing about space tugs is that we
have all the technology to do them on the shelf right now.
[...]

I can also think of a lot of ways how to implement docking in orbit.
This does not mean that any of them are easy to implement, or cheap
either.
However you do it, it involves a huge number of components, which must
work together perfectly.

Sure, but we've already done all the work, all that
we need to do is put it into practice. Look, this is
not speculation at all, Russia has built plenty of
space tugs, it's just never really used them as such.


BTW: How are you going to do maintenence on the space tug? NASA has a
hard time to maintain the shuttles engines, on earth...

This is actually really easy. You make the engines
replaceable and/or modular. Even so, since these
aren't massive, first stage engines, they should have
a long service life. The reboost engines on Mir or
ISS are not replaceable, for example, though they
have successfully gone through a large number of
firings and refuelings.

As I said, this is actually pretty straightforward
stuff. We could do it now to a limited degree with
what's on the shelf, we could do it in the near future
well with a little bit more engineering and scaling up
of certain components and aspects.

Coridon Henshaw (chenshawREMOVE@(T H+ESE)sympatico.ca) wrote:
(Christopher M. Jones) wrote in
om:

Start off with a propulsion system capable of
being refueled, rendezvous capabilities (RADAR, Lidar,
GPS, video, TDRS link, RMS, beefy / finely tuned
thrusters, etc.), add a habitable compartment (MPLM cum
Hab, or a mini-TransHab, for examples) and/or a landable
capsule (CEV) and you've duplicated just about
everything the Shuttle can do except for downmass, which
is never really used anyway. It could even do HST
servicing.

Orbit-only vehicles are obviously the way to go but unless the tug is
equipped with a fairly advanced nuclear drive, it's going to be
constrained largely to the orbital plane they were launched into. While
this would be fine for tasks that either are or can be confined to a
single orbital plane--such as the assembly of lunar or martian expedition
craft--shuttle-like vehicles will win out for one-off or rare jobs in
oddball orbits. In this context, the prime example of a rare job in an
oddball orbit is HST servicing.

Huh? Since when is the shuttle equiped with a fairly advanced nuclear drive?

There is no need to assemble - and keep re-assembling a lunar mission with
a reusable orbit-only vehicle. You can simply use it to get to moon and
back to earth orbit where it will rendezvous with a "return to earth" capsule.

--
Sander

+++ Out of cheese error +++

Sander Vesik wrote in
:

Huh? Since when is the shuttle equiped with a fairly advanced nuclear
drive?

The shuttle does gross orbital changes by landing and re-launching into a
different orbit. An orbit-only workstation/tug that is incapable of
landing does not have this option and must make all orbital maneuvers using
fuel it either already has or can be economically launched to it from the
ground.

Given the delta-v requirements for moving between, for instance, the ISS
orbit and the orbit of the Hubble, the only practical way an orbital tug
could service a large varity of orbits would be to use highly advanced
propulsion systems.

--
Coridon Henshaw - http://www3.telus.net/csbh - "I have sadly come to the
conclusion that the Bush administration will go to any lengths to deny
reality." -- Charley Reese

On Fri, 05 Mar 2004 01:55:48 GMT, "Greg D. Moore \(Strider\)"
wrote:

You can do a lot more with a handheld HP than you could do with the Apollo
computers.

Actually, you can't. The HP has more compute power but it doesn't
have the input capability the Apollo computers did. The Apollo
computers used pilot inputs and instrumentation that the HP couldn't
handle.

Mary

--
Mary Shafer Retired aerospace research engineer

(Christopher M. Jones) wrote:

(Derek Lyons) wrote in message ...
jeff findley wrote:

(Derek Lyons) writes:
The flaws in the Shuttle-ISS system are in the
implementation, not the concept.

I do not agree. The concept of the shuttle combines too many
functions into one vehicle that must return to earth after every
mission. Splitting this out into a crewed re-entry vehicle, an
orbital "space tug" (refuelled in orbit), and other vehicles is a far
better than the "one size fits all" solution that the shuttle gives
us.

So instead of returning things to earth, one tosses things not needed
at the moment overboard, and replaces them in their entirety for each
mission. I am not convinced that this is a better solution.

It is *not* a given that a re-useable has to be a "one size fits all".
You once again confuse implementation with eternal reality.

Uhhh, Derek, hate to be a kill joy but the concept
of a space tug kinda sorta implies that you have the
ability to leave stuff in orbit (including a space
tug) where you can go get it later.

Yes, it does. But Uhhh, in the system you outline above, the space
tug isn't the only vehicle.

It's not exactly like you or anyone else "tosses" their
car away when they leave it in the driveway or in
a parking space and go to work or watch a movie
or eat dinner or go to sleep. It's still there
when they get back. Think of it as a roving
space station.

Which has nothing to do with the discussion of expendables vs
reuseables.

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

(Derek Lyons) writes:

(Christopher M. Jones) wrote:
It's not exactly like you or anyone else "tosses" their
car away when they leave it in the driveway or in
a parking space and go to work or watch a movie
or eat dinner or go to sleep. It's still there
when they get back. Think of it as a roving
space station.

Which has nothing to do with the discussion of expendables vs
reuseables.

I'm currently reading "Spaceflight Revolution" by David Ashford. In
the very beginning of the book he recalls his first job interview (as
an aerospace engineer). Here is a quote from the book:

The conversation went something like this:
"How did you come to this interview, my boy?"
"I cycled sir".
"I see. How much cycling would you do if your bike were
scrapped each ride?"
"Er, not much sir".
"Quite right, my boy. Well, that is how it is with launching
satellites. They are carried on converted ballistic missiles
that can fly only once. Very expensive..."

I'm sure you'll dismiss this as well, but it's interesting to note
that this conversation took place in 1960. Isn't it nice to see that
things haven't changed much in over 40 years?

Jeff
--
Remove "no" and "spam" from email address to reply.
If it says "This is not spam!", it's surely a lie.

"jeff findley" wrote ...
(Derek Lyons) writes:
(Christopher M. Jones) wrote:
It's not exactly like you or anyone else "tosses" their
car away when they leave it in the driveway or in
a parking space and go to work or watch a movie
or eat dinner or go to sleep.

Which has nothing to do with the discussion of expendables vs
reuseables.

I'm currently reading "Spaceflight Revolution" by David Ashford. In
the very beginning of the book he recalls his first job interview (as
an aerospace engineer). Here is a quote from the book:

The conversation went something like this:
"How did you come to this interview, my boy?"
"I cycled sir".
"I see. How much cycling would you do if your bike were
scrapped each ride?"
"Er, not much sir".
"Quite right, my boy. Well, that is how it is with launching
satellites. They are carried on converted ballistic missiles
that can fly only once. Very expensive..."

I'm sure you'll dismiss this as well, but it's interesting to note
that this conversation took place in 1960. Isn't it nice to see that
things haven't changed much in over 40 years?

You mean people are still trotting out the same old tired analogies?

It's all in the numbers.

How often are payloads how large need to be launched to orbits of
what type/height?

Now if you were to tell me that (expendables/reusables)* are
_always_ going to be the 'right' solution regardless of the answer
to the previous question then I'll laugh in your face.

* pick one.

jeff findley wrote:

I'm sure you'll dismiss this as well,

Yes. Because it's another attempt by you to redefine what you are
talking about rather than adress the issues I raise.

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