Author Topic: Prompt Rendezvous - Gemini, Soyuz, and Beyond  (Read 7344 times)

Offline sdsds

  • Senior Member
  • *****
  • Posts: 5479
  • "With peace and hope for all mankind."
  • Seattle
  • Liked: 580
  • Likes Given: 677
Prompt Rendezvous - Gemini, Soyuz, and Beyond
« on: 06/29/2010 02:28 AM »
There were Gemini and Soyuz missions (and possibly others) that involved direct (i.e. first orbit) rendezvous, but no vehicle flying to ISS attempts this.  Is this because a launch anomaly would put ISS at too much risk?  It was not attempted for the Apollo/Soyuz Test Project either.

Crew taxis will benefit in several ways if prompt station rendezvouses can be part of the baseline design.  For short duration flights crew members can be more tightly packed and won't need elaborate hygiene facilities or other amenities.  The mass of batteries to provide electrical power can also be reduced if rendezvous will occur promptly.  Ditto for ECLSS consumables (oxygen, CO2 scrubbers, etc).

BEO missions that involve EOR will also benefit, as cryogenic boil-off of the Earth-departure propellant can be easily mitigated or even eliminated for shorter loiter times.

So:  are there issues with orbital mechanics that make prompt rendezvous particularly difficult?
-- sdsds --

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6180
  • Liked: 32
  • Likes Given: 0
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #1 on: 06/29/2010 02:58 AM »
There were Gemini and Soyuz missions (and possibly others) that involved direct (i.e. first orbit) rendezvous,

There was only one Gemini first-orbit rendezvous (Gemini 11, in LEO) and four Apollo first-orbit rendezvous (14-17, in LLO). I am not aware of any successful first-orbit rendezvous by Soyuz.

Quote
but no vehicle flying to ISS attempts this.  Is this because a launch anomaly would put ISS at too much risk?  It was not attempted for the Apollo/Soyuz Test Project either.

So:  are there issues with orbital mechanics that make prompt rendezvous particularly difficult?

Short and infrequent launch windows, especially when the launch site is much lower latitude than the inclination of the space station, as is the case with KSC/CCAFS launches to ISS.
JRF

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32428
  • Cape Canaveral Spaceport
  • Liked: 11171
  • Likes Given: 331
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #2 on: 06/29/2010 08:19 AM »
Gemini and Apollo had high T/W which could take out dispersions quickly.  Also the target vehicles were not sensitive to thruster blast.  Additionally, the vehicle had greater amount of dV available, making them less sensitive to errors.

Not being able to launch everyday has a impact on vehicle consumables too.  Sitting on the pad uses them up too, just as the shuttle has to replenish fuel cell reactants every so often.  The EELV pads are not going been as spacecraft friendly as the Apollo pads were and not have the same services.

« Last Edit: 06/29/2010 08:19 AM by Jim »

Offline sdsds

  • Senior Member
  • *****
  • Posts: 5479
  • "With peace and hope for all mankind."
  • Seattle
  • Liked: 580
  • Likes Given: 677
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #3 on: 06/29/2010 10:03 PM »
Thanks for the answers!

So hypothetically if there were a "seven crew to ISS" taxi vehicle it could rotate three ISS crew and also deliver a four member crew to a pre-positioned BLEO Orion.  Atlas V 551 could carry a Delta IV-H upper stage converted for use as an EDS.  Managing a "prompt" rendezvous of the ISS-departing Orion and the Cape-launched EDS would be tricky, but not impossible, i.e. the crew could take harbor at ISS if the EDS missed one or more launch windows?
-- sdsds --

Offline CitabriaFlyer

  • Full Member
  • ***
  • Posts: 308
  • Liked: 14
  • Likes Given: 0
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #4 on: 07/09/2010 04:52 AM »
I had wondered about this very question.  Although there are significant problems flying a KSC to ISS docking profile in a day or less, there is a great potential to have a vehicle that is lighter, less complex, and less costly.  It would be interesting to get a detailed analysis of the pro's and con's.

Offline brihath

  • Member
  • Full Member
  • ****
  • Posts: 877
  • Liked: 18
  • Likes Given: 20
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #5 on: 07/09/2010 11:57 AM »
As I recall, Gemini 11 performed a first orbit rendezvous to test the capability for a first orbit lunar rendevous with the LM.  The reasons that existed for that situation may be quite different than an EOR first orbit attempt, such as limited consumables in the LM, battery life, etc.

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?

Offline Lars_J

  • Senior Member
  • *****
  • Posts: 6161
  • California
  • Liked: 665
  • Likes Given: 195
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #6 on: 07/09/2010 05:51 PM »
I had wondered about this very question.  Although there are significant problems flying a KSC to ISS docking profile in a day or less, there is a great potential to have a vehicle that is lighter, less complex, and less costly.  It would be interesting to get a detailed analysis of the pro's and con's.

But you are also cutting safety margins significantly. If you design a spacecraft that has to make a 1st orbit rendezvous or abort, it ain't much of a spacecraft. I would suggest that you then have cut back margins too far.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32428
  • Cape Canaveral Spaceport
  • Liked: 11171
  • Likes Given: 331
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #7 on: 07/09/2010 06:05 PM »
I had wondered about this very question.  Although there are significant problems flying a KSC to ISS docking profile in a day or less, there is a great potential to have a vehicle that is lighter, less complex, and less costly.  It would be interesting to get a detailed analysis of the pro's and con's.

It would be heavier since it would require more propellant and larger thrusters.  And it still will have the plume issues with the target.

It is not going to be less complex, all the same systems have to be there, just less consumables and storage.
« Last Edit: 07/09/2010 06:07 PM by Jim »

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6180
  • Liked: 32
  • Likes Given: 0
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #8 on: 07/10/2010 03:41 AM »
I had wondered about this very question.  Although there are significant problems flying a KSC to ISS docking profile in a day or less, there is a great potential to have a vehicle that is lighter, less complex, and less costly.  It would be interesting to get a detailed analysis of the pro's and con's.

It would be heavier since it would require more propellant and larger thrusters.  And it still will have the plume issues with the target.

For that reason, it's probably worth pointing out that while first-orbit *rendezvous* with ISS is possible, first-orbit *docking* or *berthing* is not.

ISS requires that visiting vehicles receive a "go" to proceed inside both the Approach Ellipsoid (2x1x1 km semi-axes) and the Keep Out Sphere (200 m radius). Prior to the "go", the no-burn trajectories must be "free-drift safe" for 24 hours for the AE, and some shorter period (sorry don't have my references handy) for the KOS. This precludes a visiting vehicle targeting a direct intercept trajectory on the first orbit, as was done on Gemini 11 and Apollo 14-17. It would *not* preclude, say, a first-orbit *rendezvous* where the TPI burn targets a point just outside the AE, such that a no-burn trajectory with 3-sigma dispersions would not intersect the AE within 24 hours. But such a trajectory could not support a first-orbit docking or berthing unless the subsequent closing rates were high, and as Jim points out, that will result in plume impingement (among other issues).
JRF

Offline butters

  • Full Member
  • ****
  • Posts: 1771
  • Liked: 390
  • Likes Given: 141
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #9 on: 07/10/2010 06:51 AM »
This is where it's handy to have an orbital tug and hab module.

Then the launch/reentry vehicle could target a launch day rendezvous with the tug, which would maneuver the capsule and hab to the ISS over the next two days.  The hab would provide extended power, ECLSS and hygiene.

Like Soyuz, but with a reusable hab that stays on orbit.

Offline douglas100

  • Senior Member
  • *****
  • Posts: 2177
  • Liked: 226
  • Likes Given: 104
Douglas Clark

Offline simonbp

Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #11 on: 07/25/2010 09:25 PM »
It's not really "first-orbit rendezvous" if you use a tug. That's like saying shuttle is an SSTO with boosters; if it weren't for the boosters, it wouldn't get to orbit. Likewise, the whole point of first-orbit rendezvous is get to the station before using many consumables. If the tug has enough power & life-support that you can turn the ascent vehicle off, it's not a tug, it's a mini space station...

Offline sdsds

  • Senior Member
  • *****
  • Posts: 5479
  • "With peace and hope for all mankind."
  • Seattle
  • Liked: 580
  • Likes Given: 677
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #12 on: 07/25/2010 11:55 PM »
It's not really "first-orbit rendezvous" if you use a tug. [...] the whole point of first-orbit rendezvous is get to the station before using many consumables.

Maybe.  Or is the point of first-orbit rendezvous to not launch with many consumables?

Quote
If the tug has enough power & life-support [...], it's a mini space station...

They can call it a tug; they can call it a mini space station.  If it's a good idea then it doesn't matter too much what they call it.
-- sdsds --

Offline Danderman

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 9634
  • Liked: 364
  • Likes Given: 464
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #13 on: 07/26/2010 12:06 AM »

For that reason, it's probably worth pointing out that while first-orbit *rendezvous* with ISS is possible, first-orbit *docking* or *berthing* is not.

ISS requires that visiting vehicles receive a "go" to proceed inside both the Approach Ellipsoid (2x1x1 km semi-axes) and the Keep Out Sphere (200 m radius). Prior to the "go", the no-burn trajectories must be "free-drift safe" for 24 hours for the AE, and some shorter period (sorry don't have my references handy) for the KOS. This precludes a visiting vehicle targeting a direct intercept trajectory on the first orbit, as was done on Gemini 11 and Apollo 14-17. It would *not* preclude, say, a first-orbit *rendezvous* where the TPI burn targets a point just outside the AE, such that a no-burn trajectory with 3-sigma dispersions would not intersect the AE within 24 hours. But such a trajectory could not support a first-orbit docking or berthing unless the subsequent closing rates were high, and as Jim points out, that will result in plume impingement (among other issues).

Soyuz and Progress would seem to violate these flight rules. 

As a thought experiment, a Soyuz or Progress could perform its nominal rendezvous and dock under conditions where its ballistic targeting point was plotted out as being part of the first orbit (of course, an appropriate trajectory could only be feasible every few months, and there is no requirement for single orbit rendezvous in the ISS program).

There is a built in "go-no" decision point for Russian rendezvous, some 200 km or so out from ISS, which is turning on the Kurs box. I can't see why such a decision could not be theoretically incorporated into a single orbit rendezvous architecture. Of course, YMMV, there may be some factors I don't know about.

Offline Danderman

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 9634
  • Liked: 364
  • Likes Given: 464
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #14 on: 07/26/2010 12:07 AM »
This is where it's handy to have an orbital tug and hab module.

Then the launch/reentry vehicle could target a launch day rendezvous with the tug, which would maneuver the capsule and hab to the ISS over the next two days.  The hab would provide extended power, ECLSS and hygiene.

Like Soyuz, but with a reusable hab that stays on orbit.

This is very unlikely. The docking conditions for the assembly orbit rendezvous and the docking conditions for the final rendezvous with ISS would have to meet the flight rules, and there are much fewer launch opportunities using a dual rendezvous architecture than is usually considered.

The killer is that if there are any significant delays in the first docking, the two vehicles (tug plus cargo vehicle) are drifting away from ISS all the time. After some time, simple precession will change their orbital planes, which is not pleasant.
« Last Edit: 07/26/2010 12:10 AM by Danderman »

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6180
  • Liked: 32
  • Likes Given: 0
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #15 on: 07/26/2010 12:14 AM »

For that reason, it's probably worth pointing out that while first-orbit *rendezvous* with ISS is possible, first-orbit *docking* or *berthing* is not.

ISS requires that visiting vehicles receive a "go" to proceed inside both the Approach Ellipsoid (2x1x1 km semi-axes) and the Keep Out Sphere (200 m radius). Prior to the "go", the no-burn trajectories must be "free-drift safe" for 24 hours for the AE, and some shorter period (sorry don't have my references handy) for the KOS. This precludes a visiting vehicle targeting a direct intercept trajectory on the first orbit, as was done on Gemini 11 and Apollo 14-17. It would *not* preclude, say, a first-orbit *rendezvous* where the TPI burn targets a point just outside the AE, such that a no-burn trajectory with 3-sigma dispersions would not intersect the AE within 24 hours. But such a trajectory could not support a first-orbit docking or berthing unless the subsequent closing rates were high, and as Jim points out, that will result in plume impingement (among other issues).

Soyuz and Progress would seem to violate these flight rules.

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, including Orion.
« Last Edit: 07/26/2010 12:47 AM by Jorge »
JRF

Online mmeijeri

  • Senior Member
  • *****
  • Posts: 7454
  • Martijn Meijering
  • NL
  • Liked: 76
  • Likes Given: 169
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #16 on: 07/26/2010 12:17 AM »
All other visiting vehicles must conform to them, even Orion.

What do you mean by "even" Orion?
We will be vic-toooooo-ri-ous!!!

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6180
  • Liked: 32
  • Likes Given: 0
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #17 on: 07/26/2010 12:21 AM »
All other visiting vehicles must conform to them, even Orion.

What do you mean by "even" Orion?

It is not grandfathered despite being a NASA vehicle.
JRF

Online mmeijeri

  • Senior Member
  • *****
  • Posts: 7454
  • Martijn Meijering
  • NL
  • Liked: 76
  • Likes Given: 169
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #18 on: 07/26/2010 12:26 AM »
But why should NASA vehicles be given special treatment?
We will be vic-toooooo-ri-ous!!!

Offline Namechange User

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 7301
  • Liked: 0
  • Likes Given: 0
Re: Prompt Rendezvous - Gemini, Soyuz, and Beyond
« Reply #19 on: 07/26/2010 12:34 AM »
But why should NASA vehicles be given special treatment?

If you paid attention to what Jorge was saying, they are not. 
Enjoying viewing the forum a little better now by filtering certain users.

Tags: