Orbiting utility vehicle

"Jeff Findley" wrote in
:


"Q Leap" wrote in message
...
The vehicle must do all of the following:

Normally be fully supplied and operational immediately when needed.
Can be operated by one crew member or remotely from earth.
Match the orbit of any known object in earth orbit and return to the
space station.
Rescue by EVA the maximum projected crew that could be on a space
shuttle and the space station. (Just to cover the possibility of a
very disastrous docking maneuver.)
Serve as a backup to the current emergency crew safety measures for
the space station.

It will NOT have any capability for reentering the earth's
atmosphere. Think of it as a utility vehicle on a construction site
used to help solve unexpected problems.

If what you want is a vehicle that is based at ISS and would be
capable of changing its orbit to match Hubble, then change its orbit
to match ISS, what you're proposing is science fiction. Orbital
dynamics and the state of the art of high thrust, high efficiency
rocket engines puts such a vehicle well beyond the current state of
the art.

Agreed. The two main requirements above:

Match the orbit of any known object in earth orbit and return to the
space station.

and

Rescue by EVA the maximum projected crew that could be on a space
shuttle and the space station. (Just to cover the possibility of a
very disastrous docking maneuver.)
Serve as a backup to the current emergency crew safety measures for
the space station.

are mutually exclusive. The former requires low-thrust, high-efficiency
propulsion such as ion. The latter requires quick transfer time, which
requires high thrust.

--
JRF

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On 29 Jul 2004 00:33:42 GMT, "Jorge R. Frank"
wrote:

"Q Leap" wrote in message
...
The vehicle must do all of the following:

Normally be fully supplied and operational immediately when needed.
Can be operated by one crew member or remotely from earth.
Match the orbit of any known object in earth orbit and return to the
space station.
Rescue by EVA the maximum projected crew that could be on a space
shuttle and the space station. (Just to cover the possibility of a
very disastrous docking maneuver.)
Serve as a backup to the current emergency crew safety measures for
the space station.

It will NOT have any capability for reentering the earth's
atmosphere. Think of it as a utility vehicle on a construction site
used to help solve unexpected problems.

If what you want is a vehicle that is based at ISS and would be
capable of changing its orbit to match Hubble, then change its orbit
to match ISS, what you're proposing is science fiction. Orbital
dynamics and the state of the art of high thrust, high efficiency
rocket engines puts such a vehicle well beyond the current state of
the art.

Agreed. The two main requirements above:

Match the orbit of any known object in earth orbit and return to the
space station.

and

Rescue by EVA the maximum projected crew that could be on a space
shuttle and the space station. (Just to cover the possibility of a
very disastrous docking maneuver.)
Serve as a backup to the current emergency crew safety measures for
the space station.

are mutually exclusive. The former requires low-thrust, high-efficiency
propulsion such as ion. The latter requires quick transfer time, which
requires high thrust.

This vehicle will have high thrust and low thrust propulsion systems
on it. It must quickly reach a orbiting vehicle in trouble. The goal
is to save lives, not to use fuel in the most economical way.

Q Leap wrote in
:

On 29 Jul 2004 00:33:42 GMT, "Jorge R. Frank"
wrote:

"Q Leap" wrote in message
...
The vehicle must do all of the following:

Normally be fully supplied and operational immediately when needed.
Can be operated by one crew member or remotely from earth.
Match the orbit of any known object in earth orbit and return to the
space station.
Rescue by EVA the maximum projected crew that could be on a space
shuttle and the space station. (Just to cover the possibility of a
very disastrous docking maneuver.)
Serve as a backup to the current emergency crew safety measures for
the space station.

It will NOT have any capability for reentering the earth's
atmosphere. Think of it as a utility vehicle on a construction site
used to help solve unexpected problems.

If what you want is a vehicle that is based at ISS and would be
capable of changing its orbit to match Hubble, then change its orbit
to match ISS, what you're proposing is science fiction. Orbital
dynamics and the state of the art of high thrust, high efficiency
rocket engines puts such a vehicle well beyond the current state of
the art.

Agreed. The two main requirements above:

Match the orbit of any known object in earth orbit and return to the
space station.

and

Rescue by EVA the maximum projected crew that could be on a space
shuttle and the space station. (Just to cover the possibility of a
very disastrous docking maneuver.)
Serve as a backup to the current emergency crew safety measures for
the space station.

are mutually exclusive. The former requires low-thrust, high-efficiency
propulsion such as ion. The latter requires quick transfer time, which
requires high thrust.

This vehicle will have high thrust and low thrust propulsion systems
on it. It must quickly reach a orbiting vehicle in trouble. The goal
is to save lives, not to use fuel in the most economical way.

You did not understand what I said at all. Let me rephrase it.

You are proposing a spacecraft that can "match the orbit of any known
object in earth orbit and return to the space station." The only known
technology that can do that is low-thrust (e.g. ion) propulsion, but that
can take months. That is unacceptable for a rescue.

It is simply not practical to "match the orbit of any known object in earth
orbit and return to the space station" within the time constraints of a
rescue with *any* available propulsion technology. It is not a matter of
"us[ing] fuel in the most economical way" - the delta-V requirements to
transfer between two arbitrary orbit planes in LEO are on the order of what
it takes to get from the ground to escape velocity. So if your actual
orbiting utility vehicle is the size of, say, a Gemini capsule, your
propulsion package would have to be the same size as a rocket that could
get a Gemini from the ground to Earth escape velocity. That's a Titan III
class rocket you'd have to assemble in orbit to support your vehicle. That
is simply not practical. In order to get the propulsion package for your
vehicle down to reasonable size, you must have propulsion that is both
high-thrust *and* efficient, such as nuclear fusion or antimatter.

A slightly more realistic alternative would be to abandon your requirement
for no "capability for reentering the earth's atmosphere", and station your
utility vehicles on the *ground* with a network of launch-on-demand sites
scattered along the equator. They would launch and return the stranded crew
to the ground rather than the space station. That would be expensive but
would at least be achievable with current technology. Your current proposal
is not.

--
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 Wed, 28 Jul 2004 21:05:12 -0700, Q Leap wrote:

This vehicle will have high thrust and low thrust propulsion systems
on it. It must quickly reach a orbiting vehicle in trouble. The goal
is to save lives, not to use fuel in the most economical way.

.... and this makes it impossible.

Any current system you could define as "high-thrust" is, perforce,
incapable of reaching "any manned vehicle in orbit"...specifically
bridging the gap in inclinations between ISS and Hubble.

Those are the only two places you _might_ find a manned vehicle in the
foreseeable future.

--
Chuck Stewart
"Anime-style catgirls: Threat? Menace? Or just studying algebra?"

"Chuck Stewart" wrote in message
news
On Wed, 28 Jul 2004 21:05:12 -0700, Q Leap wrote:

This vehicle will have high thrust and low thrust propulsion systems
on it. It must quickly reach a orbiting vehicle in trouble. The goal
is to save lives, not to use fuel in the most economical way.

... and this makes it impossible.

Any current system you could define as "high-thrust" is, perforce,
incapable of reaching "any manned vehicle in orbit"...specifically
bridging the gap in inclinations between ISS and Hubble.

Those are the only two places you _might_ find a manned vehicle in the
foreseeable future.

It's good to see others agree with me. You can't match orbits with anything
in earth orbit then return to ISS *and* do this in a hurry, at least not
with today's technology. As Jorge pointed out, you can pick low thrust,
high efficiency engines (ion thrusters) or you can pick high thrust, low
efficiency engines (chemical combustion), but neither will satisfy the
requirements that QLeap wants to meet.

The only near term technology that might be able to do this would be some
form of nuclear engine. However, I don't think you'd want to spew anymore
radioactive particles into earth orbit. There's enough radiation in the Van
Allen belts already...

Jeff
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