Author Topic: Prompt Rendezvous - Gemini, Soyuz, and Beyond  (Read 7402 times)

Offline mmeijeri

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #20 on: 07/26/2010 12:39 AM »
I did in fact pay attention and asked why Jorge used the word 'even'. He replied by stating he meant not even for NASA vehicles. The use of that word suggests that there might be reason to believe (counterfactually) that NASA vehicles should get special treatment. I was inquiring into the reasons for such a counterfactual belief when you so helpfully butted in.
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Offline Danderman

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #21 on: 07/26/2010 12:40 AM »
Soyuz, Progress, and the space shuttle are grandfathered, since they have their own flight rules that predate the existence of ISS. All other visiting vehicles must conform to them, even Orion.

I understand that Progress and Soyuz are grandfathered from the VVIDD flight rules, but I am trying to figure out what in the standard Russian approach architecture actually violates the flight rules, in regards to single orbit rendezvous.  In other words, if the Russian were not able to grandfather Parom as "son of Progress", what part of their approach architecture would be rejected?

Offline Danderman

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #22 on: 07/26/2010 12:44 AM »
For a first orbit EOR, is there a strong case for it?  Given that multiple orbit rendevous to ISS seems to work well, why should it be changed?


There is only one real case to be made for single orbit rendezvous (not counting sci-fi), and that is for a launch vehicle with a robust, maneuverable upper stage mated to an ISS cargo vehicle with limited maneuver capability. In that particular configuration, the upper stage could dump the cargo vehicle somewhere "near" ISS  shortly after launch, and the cargo vehicle would perform the actual rendezvous and docking.

An example of this would be a cargo vehicle launched by Falcon 9, which would use a 2 burn maneuver to dump its payload near ISS, again pursuant to ISS flight rules.

Offline Jorge

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #23 on: 07/26/2010 12:46 AM »
Soyuz, Progress, and the space shuttle are grandfathered, since they have their own flight rules that predate the existence of ISS. All other visiting vehicles must conform to them, even Orion.

I understand that Progress and Soyuz are grandfathered from the VVIDD flight rules, but I am trying to figure out what in the standard Russian approach architecture actually violates the flight rules, in regards to single orbit rendezvous.  In other words, if the Russian were not able to grandfather Parom as "son of Progress", what part of their approach architecture would be rejected?


I think they're actually pretty close to being in compliance. The pre-DV5 trajectory conforms to the Approach Ellipsoid rule (and I think this was demonstrated on the last Progress approach abort). There is also a hold point outside 200 m that corresponds to the Keep-Out Sphere. The only catch is that the KOS rule requires that the pre-KOS trajectory be free-drift safe for a certain period (don't have my references handy but I think it's 4 hours) and I don't think the Soyuz/Progress trajectory always meets that, depending on which docking port they are aiming for.
JRF

Offline Jorge

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #24 on: 07/26/2010 12:47 AM »
I did in fact pay attention and asked why Jorge used the word 'even'. He replied by stating he meant not even for NASA vehicles. The use of that word suggests that there might be reason to believe (counterfactually) that NASA vehicles should get special treatment. I was inquiring into the reasons for such a counterfactual belief when you so helpfully butted in.

There is no such counterfactual belief. I reworded my original approach accordingly.
JRF

Offline mmeijeri

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #25 on: 07/26/2010 12:49 AM »
Thanks for the clarification.
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Offline Danderman

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #26 on: 07/26/2010 01:12 AM »
The only catch is that the KOS rule requires that the pre-KOS trajectory be free-drift safe for a certain period (don't have my references handy but I think it's 4 hours) and I don't think the Soyuz/Progress trajectory always meets that, depending on which docking port they are aiming for.

Is that 4 hours of free drift outside the KOS to make sure that the trajectory won't intercept ISS, or is it to allow Mission Control additional time to get ready for prox ops?

Offline Jorge

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #27 on: 07/26/2010 01:36 AM »
The only catch is that the KOS rule requires that the pre-KOS trajectory be free-drift safe for a certain period (don't have my references handy but I think it's 4 hours) and I don't think the Soyuz/Progress trajectory always meets that, depending on which docking port they are aiming for.

Is that 4 hours of free drift outside the KOS to make sure that the trajectory won't intercept ISS, or is it to allow Mission Control additional time to get ready for prox ops?


The former. Basically, the pre-KOS trajectory should be designed not to intersect the KOS without an active burn, such that if control over the vehicle is lost prior to being given the "go", it will drift away and not intersect the KOS for the required period.
JRF

Offline Robotbeat

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #28 on: 07/26/2010 07:24 PM »
About the plume impingement issue: Does this depend on the propellant? What about cold-gas thrusters?
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Offline Jim

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #29 on: 07/26/2010 07:27 PM »
About the plume impingement issue: Does this depend on the propellant? What about cold-gas thrusters?

No, it is not the chemical makeup of the exhaust but the high thrust that is needed.

Offline nooneofconsequence

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Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #30 on: 07/27/2010 03:09 AM »
About the plume impingement issue: Does this depend on the propellant? What about cold-gas thrusters?

No, it is not the chemical makeup of the exhaust but the high thrust that is needed.
Wow - it can carry that much momentum without dispersal in a vacuum?
What kind of plume mass/distribution scales are being considered here?
km range with newton force FOM?

add:
Conceivably, one could accurately model plume patterns and come up with a momentum distribution model that would limit/blackout certain gimbal angles or fixed thrusters for no impingement, while allowing other vector combinations to be used for maneuvering.

So you could keep to flight rules w/o the same time limits that way. Software would guarantee no impingement. 
« Last Edit: 07/27/2010 03:44 AM by nooneofconsequence »
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