|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
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 Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
#22
|
|||
|
|||
Orbiting utility vehicle
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. |
#23
|
|||
|
|||
Orbiting utility vehicle
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. |
#24
|
|||
|
|||
Orbiting utility vehicle
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?" |
#25
|
|||
|
|||
Orbiting utility vehicle
"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 -- Remove icky phrase from email address to get a valid address. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Launch of transport cargo vehicle Progress M-49 | Jacques van Oene | Space Station | 0 | May 26th 04 03:20 PM |
Landing of Soyuz TMA-3 descent vehicle | Jacques van Oene | Space Station | 0 | May 5th 04 11:23 PM |
Launch vehicle books for sale | Martin Bayer | Space Shuttle | 1 | May 2nd 04 09:32 AM |
Spirit has a mind of its own? | Jon Berndt | Space Shuttle | 33 | January 28th 04 04:48 AM |
Sad turn | Charleston | Space Shuttle | 93 | August 12th 03 02:31 AM |