Author Topic: Dragon 2 Orbital Module  (Read 18868 times)

Offline moralec

Dragon 2 Orbital Module
« on: 11/05/2014 07:20 pm »
First of all, my apologies if this is something that has been already discussed in other threads.

How reasonable and feasible would it be  for Space X to design and produce an Orbital Module for Dragon 2, in order to allow that manned capsule to perform longer missions, possibly beyond LOE (Moon, Lagrange Points, Etc.)? I'm thinking in a configuration similar to the one that is used by the Soyuz Spacecraft (image attached).

Some relevant questions to kick start the discussion:
- What possible uses can you think of for a configuration like the one described above?
- Are the super dracos powerful enough to provide abort capabilities to the capsule, even if it has another module staked on top?
- Could the NDM (or the equivalent that is being developed by SpaceX) be used to joining both parts together?
- Would it make sense to make this orbital module reusable?


Offline ChrisWilson68

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Re: Dragon 2 Orbital Module
« Reply #1 on: 11/05/2014 07:35 pm »
Who would pay for such missions?

NASA is required to use Orion for such things for political reasons, so until the political landscape changes drastically, NASA isn't paying.

SpaceX hasn't indicated any interest in paying for such missions itself.  It's focused on Mars, which will require substantially more than the small orbital module proposed here.  Any excess funds SpaceX has will go to the Mars path, not this kind of orbital module.

I don't see anyone else with the money and the will to spend it on such an orbital module.

Online butters

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Re: Dragon 2 Orbital Module
« Reply #2 on: 11/05/2014 07:39 pm »
SpaceX won't be interested in an expendable module. Dragon will be sufficient for any cislunar missions (not that they are planning any), and their strategy for Mars is to use a much larger reusable spacecraft (MCT) with accommodations for the whole round trip between the surfaces of Earth and Mars.
« Last Edit: 11/05/2014 07:40 pm by butters »

Offline MattMason

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Re: Dragon 2 Orbital Module
« Reply #3 on: 11/05/2014 08:04 pm »
Dragon takes after the American spacecraft designs.

Soyuz designs are based on separating non-life critical components from critical ones. Thus, the separated modules were made. With the notable exception of Soyuz 1 and 11, this design's worked well for the Russians over 40 years and they see no immediate need to change, even adapting it for a cargo version (Progress).

While the first man in space on a Vostok had a similar single crew compartment module with a service module-like instrument module, the US has always chosen a cockpit orientation, expanded from the Mercury days right into the Space Shuttle Orbiter's flight deck. US spacecraft modules generally kept to a manned habitable module and a single unmanned service/propulsion module (the Orbiter was a notable exception).

So, while I don't think NASA absolutely required this basic design for the Commercial Crew or Cargo programs, the Dragon isn't likely to change its design because it keeps to the one advantage of two modules: simplicity. Why design something that requires two items to jettison than just one? Soyuz cannot return home if either orbital or service module fails to jettison--a bad day. Plus, you can ensure more redundancies to remove one module, versus doubling up for two (and increasing the complexity).

EDIT: Also, Dragon is typically meant to be docked to something that handles some of the functionality of the orbital module.

Others with more engineer/history know-how might be able to correct/clarify my comment.
« Last Edit: 11/05/2014 08:05 pm by MattMason »
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Offline The_Ronin

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Re: Dragon 2 Orbital Module
« Reply #4 on: 11/05/2014 09:47 pm »
Why would they develop an orbital module when they could use BEAM or something similar?

Offline inventodoc

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Re: Dragon 2 Orbital Module
« Reply #5 on: 11/05/2014 11:01 pm »
Moralec asks an interesting question; it doesn't matter if SpaceX won't do it or if it isn't realistic to happen.

As a thought exercise, I think there would be a lot of problems with putting an orbital module on top because of LAS impact and possible aerodynamic issues (needing a fairing).

How about an Apollo style turn around and dock with an LEM approach?  You could have an interstage that serves as an orbital module and then those other issues go away?  A BEAM would be a great orbital module.
« Last Edit: 11/05/2014 11:02 pm by inventodoc »

Offline cdleonard

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Re: Dragon 2 Orbital Module
« Reply #6 on: 11/05/2014 11:58 pm »
The Soyuz is a very old design. Is the orbital module even useful when going to the ISS? Presumably you could use it to load additional cargo.

It's worth noting that proposed russian replacements for the Soyuz look more like an american conical capsule design: https://en.wikipedia.org/wiki/Prospective_Piloted_Transport_System
« Last Edit: 11/05/2014 11:58 pm by cdleonard »

Offline moralec

Re: Dragon 2 Orbital Module
« Reply #7 on: 11/06/2014 12:47 am »
Thanks to all for the valuable replies. I was not aware of that fundamental difference between american and Russian spacecraft design.

The fact that Russians are currently considering moving to a single module design is also very interesting, although surprising: Isn't it the soyuz the most reliable vehicle available? why are they going back to the drawing board instead of building on their existing approach?

I never considered the option of an Expandable Activity Module, but it makes a lot of sense. It has all the advantages of having an extra module, but without all the hassle.  Would that require a Apollo style maneuver to get it from the trunk, or could it be already attached to the hatch, but folded, to be inflated in orbit?

Offline llanitedave

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Re: Dragon 2 Orbital Module
« Reply #8 on: 11/06/2014 12:48 am »
The Soyuz is a very old design. Is the orbital module even useful when going to the ISS? Presumably you could use it to load additional cargo.

It's worth noting that proposed russian replacements for the Soyuz look more like an american conical capsule design: https://en.wikipedia.org/wiki/Prospective_Piloted_Transport_System

Sure has a very similar outline to the dragon capsule.  Seeing the development timeline, though, it may be just as likely that Dragon borrowed from it as vice versa.
« Last Edit: 11/06/2014 12:49 am by llanitedave »
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Offline guckyfan

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Re: Dragon 2 Orbital Module
« Reply #9 on: 11/06/2014 04:18 am »
I never considered the option of an Expandable Activity Module, but it makes a lot of sense. It has all the advantages of having an extra module, but without all the hassle.  Would that require a Apollo style maneuver to get it from the trunk, or could it be already attached to the hatch, but folded, to be inflated in orbit?

I remember Gwynne Shotwell made a remark quite a while back. She said they had considered building an inflatable extension into Dragon. It would be attached at the top where the mating adapter sits and could be inflated once Dragon is on course. Unfortunately I would not know how to find that statement now.

It seems they have moved past that though. Today it would be seen as a distraction from their direct way to the BFR/MCT design.

Offline NaN

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Re: Dragon 2 Orbital Module
« Reply #10 on: 11/06/2014 04:35 am »
I remember Gwynne Shotwell made a remark quite a while back. She said they had considered building an inflatable extension into Dragon. It would be attached at the top where the mating adapter sits and could be inflated once Dragon is on course. Unfortunately I would not know how to find that statement now.

It seems they have moved past that though. Today it would be seen as a distraction from their direct way to the BFR/MCT design.

Heh, I looked it up. More of an "I think this would be cool" comment than a "we considered building this". It would be cool to have a porta-Bigelow with you somehow...

http://www.popularmechanics.com/science/space/news/spacex-president-gwynne-shotwell-the-case-for-commercial-rockets-15608331
Quote from: Gwynne Shotwell
I'd love to go into space. I don't know about going to Mars—I don't like camping. But I would love to go to space for a couple days.

 What I'd love to have is some sort of inflatable structure that comes out of the top of Dragon—a clear inflatable structure. This is a visionary thing, not an engineering thing, but I can imagine popping out of the Dragon hatch into this clear sphere floating around in space.

 I don't know if I'll get the chance to go or not. It's unclear now whether SpaceX astronauts will fly or only NASA astronauts will fly, but I will make sure my employees are taken care of before me.

Offline Lars-J

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Re: Dragon 2 Orbital Module
« Reply #11 on: 11/06/2014 05:25 am »
First of all, my apologies if this is something that has been already discussed in other threads.
...
- Are the super dracos powerful enough to provide abort capabilities to the capsule, even if it has another module staked on top?

No, which makes the idea a non-starter.

Offline vt_hokie

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Re: Dragon 2 Orbital Module
« Reply #12 on: 11/06/2014 07:04 am »

SpaceX hasn't indicated any interest in paying for such missions itself.  It's focused on Mars, which will require substantially more than the small orbital module proposed here.  Any excess funds SpaceX has will go to the Mars path, not this kind of orbital module.

I've often wondered what that path is intended to be though.  I feel like the current SpaceX roadmap is basically this:

1) Crewed transport to Low Earth Orbit for ISS support
2) ?
3) Colonies on Mars!

In all seriousness, is there any architecture being defined for beyond-LEO human flights?  I don't know if SpaceX is hoping for a policy change and inclusion into a post-SLS redefined national exploration strategy.  But I'd be curious to know if there's any serious thought being given to interim milestones including cislunar flights. 

Offline jsgirald

Re: Dragon 2 Orbital Module
« Reply #13 on: 11/06/2014 11:35 am »

SpaceX hasn't indicated any interest in paying for such missions itself.  It's focused on Mars, which will require substantially more than the small orbital module proposed here.  Any excess funds SpaceX has will go to the Mars path, not this kind of orbital module.

I've often wondered what that path is intended to be though.  I feel like the current SpaceX roadmap is basically this:

1) Crewed transport to Low Earth Orbit for ISS support
2) ?
3) Colonies on Mars!

In all seriousness, is there any architecture being defined for beyond-LEO human flights?  I don't know if SpaceX is hoping for a policy change and inclusion into a post-SLS redefined national exploration strategy.  But I'd be curious to know if there's any serious thought being given to interim milestones including cislunar flights.

I find your lack of faith disturbing  ;)

Actually Spacex plans seem to be lacking at point 2 of your list. I'd also like them to be a bit more forthcoming.
I can't see what might be wrong with a bit more openness, clearly they cannot provide detailed blueprints now, but surely they must have a plan, otherwise all their Mars stuff is little more than a PR stunt.


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Offline Ben the Space Brit

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Re: Dragon 2 Orbital Module
« Reply #14 on: 11/06/2014 11:53 am »
First of all, my apologies if this is something that has been already discussed in other threads.
...
- Are the super dracos powerful enough to provide abort capabilities to the capsule, even if it has another module staked on top?

No, which makes the idea a non-starter.

I've mused on this idea myself.

Any orbital module would have to be flown in an extended-length trunk but attached to the upper stage so that the Dragon simply separates, transpositions and docks after reaching orbit. Something vaguely descended from BEAM is an obvious candidate. However, it would be a complex and expensive engineering task to turn a passive module into an operational free-flying orbital module with power, ECLSS and the like. There would have to be a serious customer willing to stump up the development cash.
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Offline hopalong

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Re: Dragon 2 Orbital Module
« Reply #15 on: 11/06/2014 12:20 pm »
The Soyuz is a very old design. Is the orbital module even useful when going to the ISS? Presumably you could use it to load additional cargo.

It's worth noting that proposed russian replacements for the Soyuz look more like an american conical capsule design: https://en.wikipedia.org/wiki/Prospective_Piloted_Transport_System

Sure has a very similar outline to the dragon capsule.  Seeing the development timeline, though, it may be just as likely that Dragon borrowed from it as vice versa.

I am not that surprised that the designs look similar, given that they will have similar specifications and have to work with the same basic environment, the designs will appear to be similar. The details will reflect more of the national styles etc.
I thinking of Shuttle / Buran, DC8 / 707. Concorde / TU-144. All complementaries of each other with similar requirements, so they look similar.

Offline JasonAW3

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Re: Dragon 2 Orbital Module
« Reply #16 on: 11/06/2014 02:13 pm »
Moralec asks an interesting question; it doesn't matter if SpaceX won't do it or if it isn't realistic to happen.

As a thought exercise, I think there would be a lot of problems with putting an orbital module on top because of LAS impact and possible aerodynamic issues (needing a fairing).

How about an Apollo style turn around and dock with an LEM approach?  You could have an interstage that serves as an orbital module and then those other issues go away?  A BEAM would be a great orbital module.

well, if they kept the trunk mostly empty, a larger BEAM might be possible, so long as it is attaced to the 2nd stage, and the Dragon 2 pulls an Apollo LEM extraction maneuver.  Not only doable, but shouldn't cut too much into overall payload.  Gotta see how it works out on the ISS first though.
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Offline guckyfan

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Re: Dragon 2 Orbital Module
« Reply #17 on: 11/06/2014 03:57 pm »
I remember Gwynne Shotwell made a remark quite a while back. She said they had considered building an inflatable extension into Dragon. It would be attached at the top where the mating adapter sits and could be inflated once Dragon is on course. Unfortunately I would not know how to find that statement now.

It seems they have moved past that though. Today it would be seen as a distraction from their direct way to the BFR/MCT design.

Heh, I looked it up. More of an "I think this would be cool" comment than a "we considered building this". It would be cool to have a porta-Bigelow with you somehow...

Thanks. You are right. It sounds like a wish to the space fairy, not like a serious engineering plan. I remembered the sentiment wrong, if not the statement. ;)

Offline solartear

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Re: Dragon 2 Orbital Module
« Reply #18 on: 11/06/2014 04:00 pm »
Soyuz basically 'needs' an orbital module because the entry module is so small. For Russia to add more seats than the three tiny ones in Soyuz, they have to stretch the entry module sideways. This results in more vertical space too, making the orbital module no longer 'necessary'. An orbital module is a nice to have feature, but it adds risk and requires a stronger launch escape system.

If SpaceX were to add an orbital module (ie, paid enough to bother), it would have to connect like the Apollo lunar module to avoid the extra risk during launch abort.

Offline dror

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Re: Dragon 2 Orbital Module
« Reply #19 on: 11/06/2014 04:43 pm »
First of all, my apologies if this is something that has been already discussed in other threads.

 - What possible uses can you think of for a configuration like the one described above?


It could work good as a Crs2 option to solve the volume issue.
If it can lower the number of flights, it could be worth the cost of RnD.
No need for LAS for CRS2.
Space is hard immensely complex and high risk !

Offline Joffan

Re: Dragon 2 Orbital Module
« Reply #20 on: 11/06/2014 05:11 pm »
First of all, my apologies if this is something that has been already discussed in other threads.
...
- Are the super dracos powerful enough to provide abort capabilities to the capsule, even if it has another module staked on top?

No, which makes the idea a non-starter.

I've mused on this idea myself.

Any orbital module would have to be flown in an extended-length trunk but attached to the upper stage so that the Dragon simply separates, transpositions and docks after reaching orbit. Something vaguely descended from BEAM is an obvious candidate. However, it would be a complex and expensive engineering task to turn a passive module into an operational free-flying orbital module with power, ECLSS and the like. There would have to be a serious customer willing to stump up the development cash.

A free-flying "trunk" doesn't need too much except a station-keeping ability for some reasonably short length of time, say an hour, while the recapture docking is taking place. But there are a lot of other issues with applying Apollo-type extraction, one obvious one being that a detached capsule has lost the power feed from the trunk, so unless it's going to re-attach the same way it was before, some other provision has to be made.

Random design speculation time...

It might be worth having a module that occupies the space and some roles of the trunk, but is mostly composed of the additional habitation module. The part immediately adjacent to the dragon, though, would be a simplified unfolding arm-type actuator module that moves the habitation module round onto the docking port. This is complicated, but it does avoid the detach/re-attach complications, since power feeds etc can run along the arm.

Dragon's attitude control already copes with the challenges of trunk-on and trunk-off modes so this should be just another variation once the hab-module is attached.

Your observations concerning cash and commitment stand unaltered ;)
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Offline guckyfan

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Re: Dragon 2 Orbital Module
« Reply #21 on: 11/06/2014 06:45 pm »

It might be worth having a module that occupies the space and some roles of the trunk, but is mostly composed of the additional habitation module. The part immediately adjacent to the dragon, though, would be a simplified unfolding arm-type actuator module that moves the habitation module round onto the docking port. This is complicated, but it does avoid the detach/re-attach complications, since power feeds etc can run along the arm.

Dragon's attitude control already copes with the challenges of trunk-on and trunk-off modes so this should be just another variation once the hab-module is attached.

Your observations concerning cash and commitment stand unaltered ;)

I see it as a major challenge to undock Dragon and trunk and then redock them after extracting the habitat. Electric connections, cooling circuits and others have to disconnect and reconnect. They are really not designed for reconnecting in space.

Maybe some modification of the idea. There was already thought of having a secondary cargo vessel with its own berthing adapter. What if the trunk is the additional habitat volume? They disconnect as Dragon and trunk do before reentry. Dragon then docks to the trunk using the docking adapter at the trunk. Necessary connections can be made manually by the astronauts.

The total weight added to the trunk may be quite low, except for additional supplies and equipment in the trunk.

Not that I believe something like this would actually be done.

Offline RanulfC

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Re: Dragon 2 Orbital Module
« Reply #22 on: 11/06/2014 07:40 pm »
Thanks to all for the valuable replies. I was not aware of that fundamental difference between american and Russian spacecraft design.

Hey there originally wasn't THAT much difference, after all we DID consider the Soyuz setup for Apollo:
http://www.astronautix.com/craft/apollod2.htm

And no those darn Soviets did NOT steal the design like they did the Shuttle :)
http://www.astronautix.com/articles/wastolen.htm

In answer to the OP I don't think that IF SpaceX were to "do" BLEO missions with the Dragon V2 that they would attach any "expansion" module directly to the Dragon. As noted that would probably be too much for the SD's to abort safetly. I very much think they would attach such to the second stage and do an on-orbit docking. Opertionally it makes more sense that way.

Randy
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Offline sdsds

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Re: Dragon 2 Orbital Module
« Reply #23 on: 11/06/2014 08:24 pm »
For a US-based "crew to LEO" system, much depends on the approach NASA takes to LEO after ISS is decommissioned. One strong possibility is that NASA will encourage (and financially support) the establishment of commercial space stations.

If that happens, having a Dragon Orbital Module that remains in orbit after the capsule returns could be a huge win.
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Offline Helodriver

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Re: Dragon 2 Orbital Module
« Reply #24 on: 11/06/2014 08:30 pm »
For a US-based "crew to LEO" system, much depends on the approach NASA takes to LEO after ISS is decommissioned. One strong possibility is that NASA will encourage (and financially support) the establishment of commercial space stations.

If that happens, having a Dragon Orbital Module that remains in orbit after the capsule returns could be a huge win.

The Tiangong solution.

Put a CBM on each end of the orbital module and grow a space station with each mission.

Offline RanulfC

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Re: Dragon 2 Orbital Module
« Reply #25 on: 11/06/2014 08:43 pm »
For a US-based "crew to LEO" system, much depends on the approach NASA takes to LEO after ISS is decommissioned. One strong possibility is that NASA will encourage (and financially support) the establishment of commercial space stations.

If that happens, having a Dragon Orbital Module that remains in orbit after the capsule returns could be a huge win.

The Tiangong solution.

Put a CBM on each end of the orbital module and grow a space station with each mission.

And hang onto the second stage and use the tanks... Wait, we already had that thread.... ;)

Randy
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Offline Bob Shaw

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Re: Dragon 2 Orbital Module
« Reply #26 on: 11/06/2014 08:49 pm »
Here's an actual, practical design for a stretched Dragon:

https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X

I am not being entirely facetious here - imagine a service/landing module with a cylindrical habitat on top, and a standard Dragon 2 above that but with a hatch in the heat shield allowing access to the habitat (you might even reduce the size of the Dragon RV slightly). Abort would be as current, but the preferred landing route would return all three modules to Earth under rocket power, with an abort capability using the capsule alone.

Offline Lars-J

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Re: Dragon 2 Orbital Module
« Reply #27 on: 11/06/2014 10:09 pm »
The simple answer is that there IS NO NEED.

Dragon 2 is just a taxi to get to a space station. Or to the Moon/L1/L2, at the most. That's just 3 days of free flight at most. And while small, it is already quite roomy compared to Soyuz.

Dragon 2 will be the equivalent of an economical small car. Why are you trying to make it into an RV for work commutes?

Offline RanulfC

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Re: Dragon 2 Orbital Module
« Reply #28 on: 11/06/2014 10:25 pm »
The simple answer is that there IS NO NEED.

Dragon 2 is just a taxi to get to a space station. Or to the Moon/L1/L2, at the most. That's just 3 days of free flight at most. And while small, it is already quite roomy compared to Soyuz.

Dragon 2 will be the equivalent of an economical small car. Why are you trying to make it into an RV for work commutes?

SUV but who's counting :)

Seriously I agree. The Dragon V2 is a LEO TAXI and really it needs to "be" nothing more. Everything else is what it's supposed to deliver people TO not in itself be :)

Randy
From The Amazing Catstronaut on the Black Arrow LV:
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Offline manboy

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Re: Dragon 2 Orbital Module
« Reply #29 on: 11/10/2014 10:28 pm »
First of all, my apologies if this is something that has been already discussed in other threads.

How reasonable and feasible would it be  for Space X to design and produce an Orbital Module for Dragon 2, in order to allow that manned capsule to perform longer missions, possibly beyond LOE (Moon, Lagrange Points, Etc.)? I'm thinking in a configuration similar to the one that is used by the Soyuz Spacecraft (image attached).

No, it would prevent the launch escape system from working. You would need to do something similar to Apollo where the Orbital Module gets launched beneath Dragon and then docks after they enter in orbit.

- Could the NDM (or the equivalent that is being developed by SpaceX) be used to joining both parts together?
It's called the NASA Docking System (NDS).
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Offline Comga

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Re: Dragon 2 Orbital Module
« Reply #30 on: 11/24/2014 09:37 pm »
First of all, my apologies if this is something that has been already discussed in other threads.

How reasonable and feasible would it be  for Space X to design and produce an Orbital Module for Dragon 2, in order to allow that manned capsule to perform longer missions, possibly beyond LOE (Moon, Lagrange Points, Etc.)? I'm thinking in a configuration similar to the one that is used by the Soyuz Spacecraft (image attached).

No, it would prevent the launch escape system from working. You would need to do something similar to Apollo where the Orbital Module gets launched beneath Dragon and then docks after they enter in orbit.

- Could the NDM (or the equivalent that is being developed by SpaceX) be used to joining both parts together?
It's called the NASA Docking System (NDS).

The Japanese have a nice solution to this, at least on paper.
The orbital module rides up behind the capsule, but attached by long arms.
In case of an abort the orbital module is left behind.
When they make it to orbit, the arms extend slightly, then swing the OM around to the front of the capsule, before retracting and berthing the OM to the capsule.
No need to control two independent spacecraft and perform a docking.
It was discussed on NSF back in 2009.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline llanitedave

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Re: Dragon 2 Orbital Module
« Reply #31 on: 11/25/2014 01:42 am »
First of all, my apologies if this is something that has been already discussed in other threads.

How reasonable and feasible would it be  for Space X to design and produce an Orbital Module for Dragon 2, in order to allow that manned capsule to perform longer missions, possibly beyond LOE (Moon, Lagrange Points, Etc.)? I'm thinking in a configuration similar to the one that is used by the Soyuz Spacecraft (image attached).

No, it would prevent the launch escape system from working. You would need to do something similar to Apollo where the Orbital Module gets launched beneath Dragon and then docks after they enter in orbit.

- Could the NDM (or the equivalent that is being developed by SpaceX) be used to joining both parts together?
It's called the NASA Docking System (NDS).

The Japanese have a nice solution to this, at least on paper.
The orbital module rides up behind the capsule, but attached by long arms.
In case of an abort the orbital module is left behind.
When they make it to orbit, the arms extend slightly, then swing the OM around to the front of the capsule, before retracting and berthing the OM to the capsule.
No need to control two independent spacecraft and perform a docking.
It was discussed on NSF back in 2009.

Does that really save weight and complexity compared to small thrusters and gyros?
"I've just abducted an alien -- now what?"

Offline Jet Black

Re: Dragon 2 Orbital Module
« Reply #32 on: 11/25/2014 01:00 pm »
Does that really save weight and complexity compared to small thrusters and gyros?

a couple of arms and motors would seem to be less complex, though conversely all the orientation stuff would already be there too, most likely.
For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled. -- Richard Feynman

Offline llanitedave

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Re: Dragon 2 Orbital Module
« Reply #33 on: 11/25/2014 03:33 pm »
Yeah, they have to put maneuvering thrusters on anyway, and all it takes is a few small puffs...
"I've just abducted an alien -- now what?"

Offline starsilk

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Re: Dragon 2 Orbital Module
« Reply #34 on: 11/25/2014 06:06 pm »
First of all, my apologies if this is something that has been already discussed in other threads.

How reasonable and feasible would it be  for Space X to design and produce an Orbital Module for Dragon 2, in order to allow that manned capsule to perform longer missions, possibly beyond LOE (Moon, Lagrange Points, Etc.)? I'm thinking in a configuration similar to the one that is used by the Soyuz Spacecraft (image attached).

No, it would prevent the launch escape system from working. You would need to do something similar to Apollo where the Orbital Module gets launched beneath Dragon and then docks after they enter in orbit.

- Could the NDM (or the equivalent that is being developed by SpaceX) be used to joining both parts together?
It's called the NASA Docking System (NDS).

The Japanese have a nice solution to this, at least on paper.
The orbital module rides up behind the capsule, but attached by long arms.
In case of an abort the orbital module is left behind.
When they make it to orbit, the arms extend slightly, then swing the OM around to the front of the capsule, before retracting and berthing the OM to the capsule.
No need to control two independent spacecraft and perform a docking.
It was discussed on NSF back in 2009.

Does that really save weight and complexity compared to small thrusters and gyros?

the point is the two vehicles are never separated - there's no independent movement and complexity involved with lining up for a docking etc.

Offline the_other_Doug

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Re: Dragon 2 Orbital Module
« Reply #35 on: 12/01/2014 12:34 am »
If you want to add an orbital module to the top of Dragon and still have your Launch Escape System (LES) able to pull the crew off the rocket, why not do it like the Russians have with Soyuz for nearly 50 years?

When a Soyuz does a launch abort, the LES rocket tower pulls the launch shroud, with the orbital module and descent module attached, off the rocket.  When the shroud/OM/DM stack has cleared the rocket's blast area, the DM is separated from the OM/shroud assembly and drops away from it, and then the DM then pops its 'chute and lands "normally."

-Doug  (With my shield, not yet upon it)
-Doug  (With my shield, not yet upon it)

Offline Lars-J

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Re: Dragon 2 Orbital Module
« Reply #36 on: 12/01/2014 05:39 am »
If you want to add an orbital module to the top of Dragon and still have your Launch Escape System (LES) able to pull the crew off the rocket, why not do it like the Russians have with Soyuz for nearly 50 years?

When a Soyuz does a launch abort, the LES rocket tower pulls the launch shroud, with the orbital module and descent module attached, off the rocket.  When the shroud/OM/DM stack has cleared the rocket's blast area, the DM is separated from the OM/shroud assembly and drops away from it, and then the DM then pops its 'chute and lands "normally."

-Doug  (With my shield, not yet upon it)

I think most of us understand how the Soyuz abort system works. And how it doesn't fit with a reusable system with a multi-purpose (abort AND landing) abort system like Dragon has. So why in the world would one weigh down Dragon with such an orbital module?

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