Author Topic: Raising ISS orbit with (super) Draco thrust  (Read 9304 times)

Online Silmfeanor

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #20 on: 05/28/2012 04:47 am »
Why couldn't Dragon be modified to attach where Progress does, to do the same kind of boosting using SuperDracos?

There is literally no reason to do this. Dragon is designed for use with the U.S. segment modifying it for use with the Russian segment would be totally unnecessary and expensive.

Well, then there should be universal docking point where anything can attach to do a station boost. Then the station can always get boosted in a pinch, if Progress or whatever else has been delayed/suspended/etc.

Is the price of that module ( think a few hundred million ) worth the expense of " it should be there" for the small, small chance that progress fails, Zvezda is empty / disabled but the space station still intact, and no ATV is docked?

Where do you place it?
Who builds it?
Who launches it?
Who pays for it?

These are not trivial questions. Reality supersedes " it should be there" or " it would be nice to have"
Spacecraft are not legos or a computergame where you can just add a part and it'll magically work. There's physics, economics and politics involved.

There should be a Sea Dragon with a VASIMR mars cycler. That way we can get to mars, if other things don't work out. And ponies.

Offline Jorge

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #21 on: 05/28/2012 04:52 am »
Why couldn't Dragon be modified to attach where Progress does, to do the same kind of boosting using SuperDracos?

There is literally no reason to do this. Dragon is designed for use with the U.S. segment modifying it for use with the Russian segment would be totally unnecessary and expensive.

Well, then there should be universal docking point where anything can attach to do a station boost. Then the station can always get boosted in a pinch, if Progress or whatever else has been delayed/suspended/etc.

The thing is, you would need to define "in a pinch" and justify why the station can't just wait for Progress. This has already been discussed at length in this thread, but I will summarize one more time.

If there is a Progress stand-down, ISS is at an orbit altitude that can survive over a year. Given that Progress launches without a crew, you'd have to have a serious non-launch issue with Progress for it to stand down that long. Soyuz stand-downs, even with the risk to the crew, have lasted less long. Any issue with Progress that also affects Soyuz for that long (launch issue, Kurs issue) would doom ISS anyway since there is currently no other crew vehicle.

If there is a lengthy Progress stand-down, Zvezda can perform reboost. Zvezda can draw propellant from Zarya, and there is enough to boost ISS well above necessary (well above the capability for any current visiting vehicle to even reach it, actually). Zvezda has two engines, so ISS could still be reboosted if one fails. And if there is a serious enough Zvezda failure to affect both engines, ISS is doomed anyway due to loss of attitude control.

So you really need to define the probability of the kind of failure scenario you're proposing here, to determine if the expense of a "universal docking joint" is worth it. The way I see it, the "window" of a failure scenario that takes out all existing reboost capability without completely dooming ISS anyway is so narrow that there's no point spending a lot of money to protect against it.
« Last Edit: 05/28/2012 04:53 am by Jorge »
JRF

Online FinalFrontier

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #22 on: 05/28/2012 05:02 am »
Why couldn't Dragon be modified to attach where Progress does, to do the same kind of boosting using SuperDracos?

There is literally no reason to do this. Dragon is designed for use with the U.S. segment modifying it for use with the Russian segment would be totally unnecessary and expensive.

Well, then there should be universal docking point where anything can attach to do a station boost. Then the station can always get boosted in a pinch, if Progress or whatever else has been delayed/suspended/etc.

Not needed never going to happen. Crew dragon will be able to conduct re-boost's (potentially) from PMA2. No need or ability to do so with cargo dragon.
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Online FinalFrontier

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #23 on: 05/28/2012 05:04 am »
Why couldn't Dragon be modified to attach where Progress does, to do the same kind of boosting using SuperDracos?

There is literally no reason to do this. Dragon is designed for use with the U.S. segment modifying it for use with the Russian segment would be totally unnecessary and expensive.

Well, then there should be universal docking point where anything can attach to do a station boost. Then the station can always get boosted in a pinch, if Progress or whatever else has been delayed/suspended/etc.

Is the price of that module ( think a few hundred million ) worth the expense of " it should be there" for the small, small chance that progress fails, Zvezda is empty / disabled but the space station still intact, and no ATV is docked?

Where do you place it?
Who builds it?
Who launches it?
Who pays for it?

These are not trivial questions. Reality supersedes " it should be there" or " it would be nice to have"
Spacecraft are not legos or a computergame where you can just add a part and it'll magically work. There's physics, economics and politics involved.

There should be a Sea Dragon with a VASIMR mars cycler. That way we can get to mars, if other things don't work out. And ponies.


You had me at Sea Dragon  ;D
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"Live Long and Prosper"

Online OneSpeed

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #24 on: 09/11/2015 11:06 pm »
first congratulation for NASA and Spacex for the nicest present
to all the space follower folk. We all dream about moon and mars ...

OK, around 2014  the last ATV mission will fly to the station.
The only orbit raising possibility for ISS stays the good old Zwezda with refueling via Progress flights.
Can the dragon with some extra fueling modifications use the draco thrusters to raise ISS orbit ?
If it makes sense  , NASA can leave maybe  a dedicated dragon ( a used one ) on nadir 2 to be used as backup  for Orbit raising.

Node 2 nadir is a crappy location for reboost, due to the large moment arm.

What's wrong with Zvezda/Progress?

Assuming there was an issue with Zvezda/Progress, another alternative would be to carry a Super Draco and fuel as an external cargo pack inside the Dragon trunk. The booster pack would then need to be moved (by the Canadarm) to a suitable location on the ISS for firing.

Offline Darren_Hensley

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #25 on: 09/11/2015 11:53 pm »
Why couldn't Dragon be modified to attach where Progress does, to do the same kind of boosting using SuperDracos?

There is literally no reason to do this. Dragon is designed for use with the U.S. segment modifying it for use with the Russian segment would be totally unnecessary and expensive.

Well, then there should be universal docking point where anything can attach to do a station boost. Then the station can always get boosted in a pinch, if Progress or whatever else has been delayed/suspended/etc.

Is the price of that module ( think a few hundred million ) worth the expense of " it should be there" for the small, small chance that progress fails, Zvezda is empty / disabled but the space station still intact, and no ATV is docked?

Where do you place it?
Who builds it?
Who launches it?
Who pays for it?

These are not trivial questions. Reality supersedes " it should be there" or " it would be nice to have"
Spacecraft are not legos or a computergame where you can just add a part and it'll magically work. There's physics, economics and politics involved.

There should be a Sea Dragon with a VASIMR mars cycler. That way we can get to mars, if other things don't work out. And ponies.

The ICM is already built, mothballed. I don't think it will ever be needed now. Too late in the game to bother.
https://books.google.com/books?id=plzgglHCV10C&pg=PA116&hl=en#v=onepage&q&f=false
« Last Edit: 09/12/2015 12:00 am by Darren_Hensley »
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Offline Jim

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #26 on: 09/12/2015 12:30 am »

Assuming there was an issue with Zvezda/Progress, another alternative would be to carry a Super Draco and fuel as an external cargo pack inside the Dragon trunk. The booster pack would then need to be moved (by the Canadarm) to a suitable location on the ISS for firing.

not really.

A.  Why does it have to be a Super Dacro or on a Dragon?
B.  How is it controlled?
c.  The only suitable locations are Zvezda aft end and Canadarm can't get there.  Or the other end, but that is only for docking.

Offline Burninate

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #27 on: 09/12/2015 06:44 am »
A single Super Draco at its lowest throttle setting would likely tear the ISS apart.  ISS reboost doesn't use anywhere near that amount of thrust, and the load paths of the fully built structure are not sufficiently resilient to take it.

The low end on thrust for ISS reboost, the amount of drag it has to fight, is in the vicinity of 250milliNewtons;  The low end on thrust from the smallest maneuvering thrusters is 500x higher IIRC.  The smallest thrusters are still more than sufficient.

  from 2010 gives 0.0185m/s^2 acceleration over a 2.7m/s burn.  At the time the station weighed about 370 metric tons;  This represents ~6845N in total.  Not sure on the specifics of which thrusters were used.

Here's another burn from the ATV in 2008 at 0.0034m/s^2 acceleration over a 4.05m/s burn: http://www.spaceref.com/news/viewpr.html?pid=25725 .  At the time the station weighed about 300 metric tons;  This represents  ~1014N thrust.
« Last Edit: 09/12/2015 07:32 am by Burninate »

Offline litton4

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #28 on: 09/12/2015 10:19 am »
I believe the Shuttle RCS which was used for reboosts produce about 3800N (The verniers were about 100N)

Min thrust on a SD is apparently about 14,000 N
« Last Edit: 09/12/2015 10:22 am by litton4 »
Dave Condliffe

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #29 on: 09/12/2015 12:08 pm »

Assuming there was an issue with Zvezda/Progress, another alternative would be to carry a Super Draco and fuel as an external cargo pack inside the Dragon trunk. The booster pack would then need to be moved (by the Canadarm) to a suitable location on the ISS for firing.

not really.

A.  Why does it have to be a Super Dacro or on a Dragon?
B.  How is it controlled?
c.  The only suitable locations are Zvezda aft end and Canadarm can't get there.  Or the other end, but that is only for docking.

Thanks for your reply.

A. It doesn't have to be a Super Draco (from other replies a standard Draco or two would be sufficient for the task), but it does have to be one or the other because that's the thread topic.

B and C. My understanding is that the thrust needs to be aimed at the centre of gravity of the ISS, otherwise  rotation of the ISS will be induced. Are there existing nadir hardware mounting points near the ISS centre of gravity (in the US segment?). e.g. could existing handrail or shield attachment points and power connectors not be repurposed? Could the thruster not be controlled remotely with a suitable wireless device from the cupola?

An advantage I see with this approach is that a permanent reboost / debris avoidance capability could be made permanently available to the ISS.

Offline Jim

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Re: Raising ISS orbit with (super) Draco thrust
« Reply #30 on: 09/12/2015 01:37 pm »

1.  Are there existing nadir hardware mounting points near the ISS centre of gravity (in the US segment?).

2.   e.g. could existing handrail or shield attachment points and power connectors not be repurposed?

3. Could the thruster not be controlled remotely with a suitable wireless device from the cupola?


1.  No, and still the wrong direction.

2.  Needs to be more robust than these would provide.  What power connectors?

3.  No, not reliable enough.  And the thruster pod would have to be continuously powered to receive signals at any time.

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