Author Topic: US Segment Propulsion and Control Module Technology  (Read 28821 times)

Offline Jim

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Re: US Segment Propulsion and Control Module Technology
« Reply #60 on: 07/04/2014 07:20 pm »
If you tripled the order for the 650kg European Robotic Arm, and launched a pair of the (somewhere between 100 and 500kg) phase 1 prototype 20kw ROSA solar array winglets that NASA has already funded construction of, and sent up an extra ton of nickel-hydrogen batteries, and a pair of 7kw NEXT ion thrusters (100kg) that have already been extensively tested & flight-qualified, and 2 tons of xenon propellant, you could reboost the ISS for around 10 years at the present altitude, for 5400kg of payload.  Add on 1T of storeable propellant for the ~1 emergency debris avoidance burn per year and you've got yourself a solution in two Dragon Cargo launches.

Huh?

What the heck are the arms for?
And what says the ISS can control more than 1?
What nickel-hydrogen batteries?  the ISS is moving away from them.
No CMG desat.
Hence this is no solution.

Also, constant thrust is not a viable solution.
« Last Edit: 07/04/2014 07:22 pm by Jim »

Offline baldusi

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Re: US Segment Propulsion and Control Module Technology
« Reply #61 on: 07/04/2014 07:48 pm »
Also, constant thrust is not a viable solution.
I won't mean an absolute solution for everything. You'd wan to do desats and DAMs. But I've been wondering if you could use SEP to exactly counteract the aero drag. Wouldn't that actually improve microgravity and solve the altitude loss problem?

Offline RonM

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Re: US Segment Propulsion and Control Module Technology
« Reply #62 on: 07/04/2014 07:56 pm »
Also, constant thrust is not a viable solution.
I won't mean an absolute solution for everything. You'd wan to do desats and DAMs. But I've been wondering if you could use SEP to exactly counteract the aero drag. Wouldn't that actually improve microgravity and solve the altitude loss problem?

But how steady is the thrust from SEP? It could easily add small vibrations and degrade the microgravity environment. Better off coasting and use the occasional burn to raise the station.

Offline baldusi

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Re: US Segment Propulsion and Control Module Technology
« Reply #63 on: 07/04/2014 08:04 pm »
Also, constant thrust is not a viable solution.
I won't mean an absolute solution for everything. You'd wan to do desats and DAMs. But I've been wondering if you could use SEP to exactly counteract the aero drag. Wouldn't that actually improve microgravity and solve the altitude loss problem?

But how steady is the thrust from SEP? It could easily add small vibrations and degrade the microgravity environment. Better off coasting and use the occasional burn to raise the station.
Are you aware that we are talking about >1N thrust for a 400 tonne station?

Offline hop

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Re: US Segment Propulsion and Control Module Technology
« Reply #64 on: 07/04/2014 08:07 pm »
But how steady is the thrust from SEP? It could easily add small vibrations and degrade the microgravity environment.
In principle, it can be extremely good, GOCE for example. However, that doesn't mean such an approach is viable for the ISS.

Offline Sean Lynch

Re: US Segment Propulsion and Control Module Technology
« Reply #65 on: 07/05/2014 03:20 am »
An even better example of ISS oscillations than the Tacoma Narrows Bridge, is video of resonance affecting the ISS itself.
The resonance was caused by a programming error according to the article below.
Here's the story:
http://www.nbcnews.com/id/28998876/#story
edit
Attached the video
Here's an old but good CBS article on extending the life of the station perhaps beyond 2028.

Here are some links to papers on ISS dynamics and modal analysis that illustrate some of the challenges ISS faces. Not specific to resonance necessarily, but these papers give good food for thought regarding the complexities one has to deal with in space. Space is hard.

ISS STAGE 12A POST-FLIGHT MODAL ANALYSIS, MODEL VALIDATION AND CORRELATION
See Chapter One in this Journal:
International Space Station 2A Array Modal Analysis
I recall reading some really good documents from Boeing about ISS structural considerations that I'll try to provide links to.
« Last Edit: 07/07/2014 05:43 am by Sean Lynch »
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Offline Sean Lynch

Re: US Segment Propulsion and Control Module Technology
« Reply #66 on: 07/05/2014 06:13 am »
Attached is an interesting concept: ISS Electrodynamic Tether Reboost Study.
It's good to use our imaginations in thinking of ways to keep ISS flying. SEP, VASIMIR, Solar Sails, or even political solutions such as PFOP (pork fueled oars and paddles).
 
Having said that, it would be better in my opinion to keep things as simple as possible because time is not our friend.
CST-100 offers a huge advantage over Dragon V2 if CST-100 can provide ISS reboost:
http://forum.nasaspaceflight.com/index.php?topic=22125.msg928528#msg928528

We need a near term fix, but let's encourage bright minds to imagine long term solutions that may be deployed in the future.

Even if we can use visiting vehicles for reboost, ISS still requires independent means of reboost and collision avoidance in case of launch disasters, etc.

Quote
-As long as we are imagining, I would imagine the best way to keep ISS flying past 2020 is to invite China to participate in the ISS, but perhaps it's too late if Russia and China are already making plans.
-angst
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Offline Prober

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Re: US Segment Propulsion and Control Module Technology
« Reply #67 on: 07/05/2014 06:37 pm »
If you tripled the order for the 650kg European Robotic Arm, and launched a pair of the (somewhere between 100 and 500kg) phase 1 prototype 20kw ROSA solar array winglets that NASA has already funded construction of, and sent up an extra ton of nickel-hydrogen batteries, and a pair of 7kw NEXT ion thrusters (100kg) that have already been extensively tested & flight-qualified, and 2 tons of xenon propellant, you could reboost the ISS for around 10 years at the present altitude, for 5400kg of payload.  Add on 1T of storeable propellant for the ~1 emergency debris avoidance burn per year and you've got yourself a solution in two Dragon Cargo launches.
Appreciate your solution oriented comment Burninate. I love the idea of using solar electric propulsion.
I assume by "storable propellant" for collision avoidance you mean Xenon?
We need to know today if the Russians are really planning on quitting the ISS and if they are planning on taking Zvezda with them, because the dynamics and harmonics of the ISS are complicated.

Would the propulsion systems be attached to the Z-truss? Can Dextre climb "up" there?
Perhaps someone reading this has a friend at Boeing familiar with ISS dynamics that could help us out.
1 ton of hypergolic propellant at 235s Isp (this is from SuperDraco, we don't have numbers for the Draco) provides only ~5.5m/s boost, and I'm not counting on the lifetime of the thruster to be very long - just be there for an extra 1-2m/s in an emergency.  2 tons of xenon at 4100s Isp provide 191m/s, which would fight aerodynamic drag to maintain altitude.

sounds expensive....what does 2 tons of xenon cost?
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Offline RonM

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Re: US Segment Propulsion and Control Module Technology
« Reply #68 on: 07/05/2014 06:56 pm »
Also, constant thrust is not a viable solution.
I won't mean an absolute solution for everything. You'd wan to do desats and DAMs. But I've been wondering if you could use SEP to exactly counteract the aero drag. Wouldn't that actually improve microgravity and solve the altitude loss problem?

But how steady is the thrust from SEP? It could easily add small vibrations and degrade the microgravity environment. Better off coasting and use the occasional burn to raise the station.
Are you aware that we are talking about >1N thrust for a 400 tonne station?

No, you didn't mention that. Nor did you answer my question.

Offline RonM

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Re: US Segment Propulsion and Control Module Technology
« Reply #69 on: 07/05/2014 06:57 pm »
But how steady is the thrust from SEP? It could easily add small vibrations and degrade the microgravity environment.
In principle, it can be extremely good, GOCE for example. However, that doesn't mean such an approach is viable for the ISS.

Now that is a good answer.

Offline Danderman

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Re: US Segment Propulsion and Control Module Technology
« Reply #70 on: 07/06/2014 12:31 am »
The cheapest approach would be to have US cargo vehicles provide reboost and roll control, much as Progress does today.

Please advise why Progress can perform these functions, but Dragon or Cygnus cannot.
« Last Edit: 07/06/2014 12:31 am by Danderman »

Offline Jim

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Re: US Segment Propulsion and Control Module Technology
« Reply #71 on: 07/06/2014 03:14 am »
The cheapest approach would be to have US cargo vehicles provide reboost and roll control, much as Progress does today.

Please advise why Progress can perform these functions, but Dragon or Cygnus cannot.


There are many reasons that Dragon or Cygnus cannot perform the function and they are intuitively obvious to the most causal of observers. 

Offline Lar

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Re: US Segment Propulsion and Control Module Technology
« Reply #72 on: 07/06/2014 03:53 am »
Take pity on us with a brief recounting, if you would, Jim...
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Burninate

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Re: US Segment Propulsion and Control Module Technology
« Reply #73 on: 07/06/2014 08:08 am »
Attached is an interesting concept: ISS Electrodynamic Tether Reboost Study.
It's good to use our imaginations in thinking of ways to keep ISS flying. SEP, VASIMIR, Solar Sails, or even political solutions such as PFOP (pork fueled oars and paddles).
 
Having said that, it would be better in my opinion to keep things as simple as possible because time is not our friend.
CST-100 offers a huge advantage over Dragon V2 if CST-100 can provide ISS reboost:
http://forum.nasaspaceflight.com/index.php?topic=22125.msg928528#msg928528

We need a near term fix, but let's encourage bright minds to imagine long term solutions that may be deployed in the future.

Even if we can use visiting vehicles for reboost, ISS still requires independent means of reboost and collision avoidance in case of launch disasters, etc.

Quote
-As long as we are imagining, I would imagine the best way to keep ISS flying past 2020 is to invite China to participate in the ISS, but perhaps it's too late if Russia and China are already making plans.
-angst
I don't think this requires much imagination, just piecing together the available parts.  SEP is *here*.  Ion thrusters are *already used* for stationkeeping, frequently, in the commercial sector, with COTS parts.  NASA has developed its high-performance parts in parallel to high TRL, has flown several SEP missions, and is itching for demonstrator missions for the next generation (or, really, this generation) of hardware.

ED tethers are poorly demonstrated despite several attempts, and the most promising ones are not gravity-gradient stabilized, but spin stabilized.

If you tripled the order for the 650kg European Robotic Arm, and launched a pair of the (somewhere between 100 and 500kg) phase 1 prototype 20kw ROSA solar array winglets that NASA has already funded construction of, and sent up an extra ton of nickel-hydrogen batteries, and a pair of 7kw NEXT ion thrusters (100kg) that have already been extensively tested & flight-qualified, and 2 tons of xenon propellant, you could reboost the ISS for around 10 years at the present altitude, for 5400kg of payload.  Add on 1T of storeable propellant for the ~1 emergency debris avoidance burn per year and you've got yourself a solution in two Dragon Cargo launches.

Huh?

What the heck are the arms for?
And what says the ISS can control more than 1?
What nickel-hydrogen batteries?  the ISS is moving away from them.
No CMG desat.
Hence this is no solution.

Also, constant thrust is not a viable solution.

Answer in new thread.  Arms are overkill gimbals with translation.  NiH batts because I assumed that was the default.  CMG desat via off-axis gimballing.  Arm control is a matter of software.  Constant thrust seems a perfectly viable solution.

« Last Edit: 07/06/2014 08:21 am by Burninate »

Offline Jim

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Re: US Segment Propulsion and Control Module Technology
« Reply #74 on: 07/06/2014 04:29 pm »

Answer in new thread.  Arms are overkill gimbals with translation.  NiH batts because I assumed that was the default.  CMG desat via off-axis gimballing.  Arm control is a matter of software.  Constant thrust seems a perfectly viable solution.


Just handwaving.  You did not adequately  defend your position.

Offline Remes

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Re: US Segment Propulsion and Control Module Technology
« Reply #75 on: 07/07/2014 01:18 am »
The ATV had 4 thrusters with 490N. Dumb latching valves, nothing fancy. I don't think there are any issues with harmonics et al. Progress also didn't have anything fancy, which couldn't be provided with couple centuries old technology (not that ATV is much newer). If you start with solar propulsion or other fancy things you are adding tremendous costs and risk.

Yes, I agree that you don't just put a few fuel tanks in a dragon and let it fly (with few standard dracos in the trunk). There are costs, there is qualification, etc. Most likely the Dracos are not designed to work over month in space (don't know the life time of a dragon anyway, so even more qualification costs). The four main thrusters of ATV are Aerojet intellectual property, so easily available to SpaceX. The Dragon could be stripped down (no heatshield, if it saves money and does not add requalification cost).

Cost and effort are there and must be judged against loosing 4 or 8 years of ISS life. Most likely beeing a fact, that after ISS for some time there will be nothing comparable to it.

Reboost could be also provided over CBMs, if the ISS is oriented in the right way (180 degrees around y e.g., if the front port ist used). The CBMs were carrying anyway the reboost force of ATV/PROGRESS, .., furthermore 4*490N is really not that much compared to a few hundred tons (and compared against thermal stresses, bending moments, etc).

Anyway, hope relations become normal in one or two years time and everything is only a thought experiment.

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