What advances have been made since Apollo?

(Henry Spencer) writes:

It would be silly to build docking and maneuvering equipment into each
module, or to include a removable tug on each launch. Far more sensible
is to have a single tug based in orbit, which goes and gets each module
and brings it back. (This also lets you launch the modules into an orbit
lower than the assembly orbit, increasing launcher payload. Yes, it's a
net increase even after allowing for the need to ship up tug fuel.)

Others should note that you can leave the tug in orbit and that such a
tug could feature an RMS (or two) which would enable the use of
berthing mechanisms instead of (usually heavier) docking mechanisms.
There is no need to bring your tug back to earth on each flight (as is
done with the shuttle).

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

(Derek Lyons) writes:

Hopefully NASA has learned something from MIR as well. Docking
modules together carries a large hidden cost in the deadweight and
non-reusability of the docking and maneuvering systems.

As I said in another post (which added to Henry's discussion of a
space tug to take payloads from a low parking orbit to a higher
assembly orbit):

You can leave a tug in orbit and such a tug could feature an RMS (or
two) which would enable the use of berthing mechanisms instead of
(usually heavier) docking mechanisms. There is no need to bring your
tug back to earth on each flight (as is done with the shuttle).

If you do assembly this way, you don't *have* to have docking or
maneuvering equipment on each and every payload you launch.

Doing things in space for the lowest reasonable cost requires analysis
and design, not knee-jerk rejection of something because 'NASA did it
that way'.

Agreed.

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.

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

(Henry Spencer) wrote in message ...
[snip-o-rama]
It would be silly to build docking and maneuvering equipment into each
module, or to include a removable tug on each launch. Far more sensible
is to have a single tug based in orbit, which goes and gets each module
and brings it back. (This also lets you launch the modules into an orbit
lower than the assembly orbit, increasing launcher payload. Yes, it's a
net increase even after allowing for the need to ship up tug fuel.)

I can think of about a gazillion ways that this could be
done well. An idea I like particularly is a mixture
between the Russian rendezvous plus docking techniques
and the US delivery then berthing techniques. You have
a tug which can fly to and rendezvous with various objects
and attach to particular fixtures which are different from
the docking or berthing fixtures. Berthing / assembly
is then performed using some sort of RMS located at
either the point of assembly or on the tug.

For example, each payload would have a berthing or docking
point as well as an attachment point (which might merely
be an adaptor added to the berthing point). The tug would
rendezvous with the payload and attach to it, then take
the payload to the assembly and rendezvous and attach to
it, then the payload can be manipulated and berthed to the
assembly. The main advantage of this is that your berthing
fixtures don't necessarily need to serve as docking
fixtures, which comes with quite a few disadvantages.
The Shuttle does something similar now in that it attaches
to grapple points on payloads (which it usually takes along
rather than having to rendezvous with, though it has the
ability to do that) and it has a station attachment and
docking point (APAS). All this allows the payload to use
whatever is most convenient and most suitable for assembly
or berthing (CBM, truss joint, etc.) Mir used something
similar as well, new modules would dock at the central port
and would later be moved to radial ports.

I kinda like the idea of a modular propulsion system too,
but more just 'cause I think it's neat.


Anywho, the amazing thing about space tugs is that we
have all the technology to do them on the shelf right now.
Pretty much all we have to do is put the technologies
together in the right way and we're there. The fact
that we have yet to do this sort of thing is probably on
the short list of facts proving how limited and
uninnovative our space activities have become.



P.S. Tugs are one of the ways you can match just about
all of the capabilities of the Shuttle without the
huge disadvantages of the Shuttle system (like the $10k
per kg payload cost). The key is eliminating unnecessary
hardware/mass and maximizing the usefulness and
efficiency of orbital hardware. For example, are wings
or SSMEs useful on orbit? Nope. Is an SRMS or the
radiators or even the SSMEs useful on landing and reentry?
Nope. Yet the Shuttle drags them to and fro regardless.
Think of how many times an SRMS has been launched into
orbit and then landed back on Earth. Even at the ~$4k
per kg launch costs of the orbiter plus payload this is
rediculous. You could fairly easily build an orbital
equivalent Shuttle in pieces using ELVs, at much less
cost. 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. Since it could be lighter than a Shuttle
(no wings, no SSMEs, no airframe, no rudder, no landing
gear, no cargo bay) and since the propellant could be
launched separately it could have tremendous on orbit
delta V. A moderate WAG based on some simple BOTE
calcs give an on orbit mass around 20 tonnes, and a
potential delta V per propellant delivery up to around
3-ish km/s, which is enough to go lots of places in
orbit, and back.

"Dr. O" dr.o@xxxxx wrote in message
...

http://www.space.com/businesstechnol..._040303-2.html

This article claims that most of the infrastructure of the Apollo era is
still and place and 'enormous advances have been made' since. But except
for
some faster computers, the required technology is still very similar, if
not
identical. Besides, the large moon rockets have been scrapped, so this
time
most likely we'll need to do it by assembling the lunar craft in orbit
(designing a 'new' Saturn V-like vehicle would be way too expensive).

Just because a new lunar capsule will have a newer, snazzy computer
doesn't
make it fundamentally better, IMHO. What breakthrough advances have there
been since Apollo that will enable us to do it better (and hopefully
cheaper) this time?

The real advantage of newer snazzy computers and some other items is mass.

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

Simply by using modern electronics one can most likely eliminate large
amounts of mass used for the computer itself and the associated cooling and
power.

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.

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

(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. 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.

Ken Arromdee wrote:
I just read this article, and I've been wondering. Like just about everyone
else, I've been rather cynical about the chances of a moon/Mars mission being
anything but an excuse to cut everything else now. But the way this article
reads--Boeing and Lockheed-Martin providing hardware, talks about what NASA
(rather than Bush) wants to do with a moon mission, etc.--suggests it's a
real possibility. *Is* there a chance the moon plan could amount to something
more than a budget cut?

Yes - it can be another set of flags and footprints. It could even be a set of
good science missions to Moon. But forget the moonbase.

--
Sander

+++ Out of cheese error +++

On Sat, 6 Mar 2004 20:13:28 +0000 (UTC), in a place far, far away,
Sander Vesik made the phosphor on my
monitor glow in such a way as to indicate that:

Yes - it can be another set of flags and footprints. It could even be a set of
good science missions to Moon. But forget the moonbase.

Why?

(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.

Nuclear propulsion changes things greatly, of course. Even something as
simple as a restartable, refulable version of NERVA would open up a lot of
possibilities in the area of orbit-only reusable vehicles. Pie in the sky
options, like NSWR or open-cycle gas core fission would blow the doors off
if only they could be made, and made not to do it literally...


--
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

Christopher M. Jones wrote:
[...]
It would be silly to build docking and maneuvering equipment into each
module, or to include a removable tug on each launch. Far more
sensible is to have a single tug based in orbit, which goes and gets
each module
and brings it back. (This also lets you launch the modules into an
orbit
lower than the assembly orbit, increasing launcher payload. Yes, it's
a net increase even after allowing for the need to ship up tug fuel.)

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.

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

Robert Kitzmueller