Author Topic: Dragon trunk reuse/stockpile  (Read 36758 times)

Offline Ludus

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Dragon trunk reuse/stockpile
« on: 07/13/2012 06:19 pm »
I've been searching for existing discussion of this but sofar no luck. Are there proposals to keep the Dragon trunk and PV arrays on station at the ISS or future commercial stations? Are there technical issues that cause problems with this?

Just noting that Spacex will be doing a lot of missions in the very near future where the trunk and it's impressive power generation capacity are apparently going to be thrown away each time. 10 resupply missions would be 40 kw or so of power that somebody would likely pay for even if the ISS doesn't formally need it.

If spacex built the trunks to daisychain easily the one element of their launch system so far with no potential reusability would be covered. What are the issues with this?
« Last Edit: 07/13/2012 07:25 pm by Ludus »

Offline RocketmanUS

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Re: Dragon trunk reuse/stockpile
« Reply #1 on: 07/13/2012 06:32 pm »
Yes the solar panels would make for a great commodity.

If the made the solar panels to be able to be disconnected by a robotic arm and reconnected else were then that would be good.

The Dragon capsule batteries would have to have enough power then to bring it's self back to Earth without the solar panels.

Reusing the trunk, maybe, maybe not. It is to be used also to dispose of unpressurized waste. If on a given mission it is not then it might be able to be used as an unpressurized storage area for a station.

Being able to reuse the radiators would be nice too. Don't know how long Dragon can go without the radiators. Or how hard it would be to reconnect then to a station.

Offline Ludus

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Re: Dragon trunk reuse/stockpile
« Reply #2 on: 07/13/2012 06:45 pm »
I think the trunk is now jettisoned before reentry anyway. No need to remove the PV wings if the trunks can be coupled together as is in series ready to use as a solar power system with x segments. I think the other resupply systems from the Russians, ESA, Japanese provide ample trash disposal from non-reusable craft.

Offline spectre9

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Re: Dragon trunk reuse/stockpile
« Reply #3 on: 07/13/2012 07:36 pm »
Too much work required.

Astronauts are very busy.

If more power is needed it's the Russians that have the problem. They would launch the SPP not try to recycle Dragon solar panels.

Offline Ludus

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Re: Dragon trunk reuse/stockpile
« Reply #4 on: 07/13/2012 07:42 pm »
...but if the trunk was engineered to couple in a daisy chain and provide power in series the effort might be quite limited.

Offline Ludus

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Re: Dragon trunk reuse/stockpile
« Reply #5 on: 07/13/2012 07:51 pm »
Picture a caterpillar like daisy chain of trunks coupled together with pre-made physical, electrical and data links. They wouldn't add very much weight but would allow simple lego style coupling of the trunks. Considering the current cost per kg tothe ISS, astronaut labor would be pretty well compensated to save a very valuable resource.

Offline Lars_J

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Re: Dragon trunk reuse/stockpile
« Reply #6 on: 07/13/2012 07:52 pm »
But... why? The amount of changes needed alone should make this a non-starter. The hardware is not rated for extended operations (over a regular 210 day mission span).

If ISS needs more power, build some purpose-built arrays and launch them.

Offline dcporter

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Re: Dragon trunk reuse/stockpile
« Reply #7 on: 07/13/2012 07:54 pm »
Cue Jim from offstage left - "ROOOOCKETS ARRREN'T LEGOOOOS!"

This isn't going to happen in the next few iterations of anything, but a good solid total-engineering-speculation thread never hurt anybody... as long as it's properly disclaimed. =)

Offline Ludus

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Re: Dragon trunk reuse/stockpile
« Reply #8 on: 07/13/2012 08:00 pm »
Becuz it's an almost free resource vs. a project costing 10k $ per kg otherwise.

Besides, it isnot just about the ISS requirements. 210 days is jist an arbitrary spec. PV cells and systems are not likely to degrade over useful time spans..years. Other space stations might be very willing to pay for the resource.

Offline Lars_J

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Re: Dragon trunk reuse/stockpile
« Reply #9 on: 07/13/2012 08:05 pm »
Even if it was "almost free" it is still... not smart at all.

While Dragon can operate for a few hours without its trunk, it would not be prudent. If a problem develops after leaving ISS that prevents deorbit, the trunk will be needed to A) allow time to work around the issue or B) allow time get back to the ISS.

It just is a bad idea. Period. Let it go.

Offline RocketmanUS

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Re: Dragon trunk reuse/stockpile
« Reply #10 on: 07/13/2012 08:14 pm »
I'm figuring on all robotic Arm(s) to handle the job of moving the panels and or the trunk into a permanent in space use. It could be done , reuse of the radiators could need a space walk.

It does not have to be ISS.
1 ) new LEO station ( gov. or commercial )
2 ) EML1/2
3 ) SEP
4 ) Mars One transhab concept
5 ) panels sent to Lunar or Mars surface

Solar panels could be made to do both jobs if there is an order for them.
There could even be an order for a new trunk that would be designed for long in space use. There would have to be a customer for it and willing to pay for it.

If ISS panel(s) we damaged and need replacing this could be an option for the ISS team to look at.

One possible configuration could be to stake each trunk one on top of the other. A side hatch for added unpressurized storage. Mounts at top and bottom of each trunk. The whole assemble would rotate as one unit as needed.

Best to use panels from a cargo Dragon for safety and not a crew Dragon ( at least both panels and trunk ).

Offline Ludus

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Re: Dragon trunk reuse/stockpile
« Reply #11 on: 07/13/2012 08:16 pm »
That sounds like an informed objection. If Dragon needs the trunk after departure and therefore has to jettison it rather than leaving it as a resource I defer.

Offline Ludus

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Re: Dragon trunk reuse/stockpile
« Reply #12 on: 07/13/2012 08:39 pm »
i  cerrtainly accept that if the PV arrays are necessary for reasonable scenarios right up to reentry that they just have to be sacrificed. I still am curious if this has been explored or just summarily rejected on that basis. How much battery/fuel cell back-up is needed given that US spacecraft never had PV capacity at all historically?

I'm not advocating any reduction in man-rated safety, just reduction in waste where it doesn't serve any real purpose. On resupply missions for example it's reasonable to balance the probability of mission failure for return of experiments and such vs. the value of retaining the power capacity.

Offline go4mars

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Re: Dragon trunk reuse/stockpile
« Reply #13 on: 07/13/2012 08:50 pm »
Might the dragon wings be clipped short for re-entry, with only some panels stockpiled?  Or tug one off, leaving the other for re-entry?

Then again, I suppose if SpaceX sees reusability as imminent, then just sending more hardware up later would be cheaper than all that fooling around (which is currently costly). 
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline ChefPat

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Re: Dragon trunk reuse/stockpile
« Reply #14 on: 07/13/2012 08:54 pm »
In a previous thread it was asked if the Trunk could be saved for the basis of an SEP tug & IIRC, the Dragon needs it for the Radiators & electric power for maneuvering for reentry.
Playing Politics with Commercial Crew is Un-American!!!

Offline edkyle99

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Re: Dragon trunk reuse/stockpile
« Reply #15 on: 07/13/2012 08:58 pm »
This is an interesting idea, but it would require a lot of work on electrical standardization to make it work.  Something like this might help if ISS suffered an array failure, but only if it could be adapted to the ISS system to act like an "emergency generator".  (I have generators on my mind after suffering a storm-caused four-day power outage last week during the 100-105 F Midwest heat wave.  Our governor asked us yesterday, apparently having exhausted all of his executive power, to pray for rain!)

But only SpaceX could make this work, if it wanted to make this work.  The trunks are useless without a controlled spacecraft bus attached, and Dragon probably needs it until the last hour.  So there would have to be a plan and a business case for reuse, for some sensible purpose (a commercial station, a cheap satellite, etc.)  that probably also would require Dragon changes.

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Offline dwightlooi

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Re: Dragon trunk reuse/stockpile
« Reply #16 on: 07/13/2012 09:06 pm »
Forget about the ISS using the robotic arm to attach the trunk or its array in a daisy chain. Just have the Dragon (which has its own RCS) depart the station with the trunk attached, fly over to the column of previously flown trunks and docket the trunk with the chain on its own. The dragon then separates and re-enters the atmosphere on its own leaving a stack of trunks and solar arrays in space to serve as a power station for future projects.

Who cares if shit and other waste products from the ISS is burned up in a re-entry or kept on a nearby station in space? It doesn't cost anything to keep it there. Also, who cares if the solar array assembly also happens to carry feces in its trunks? Just attach a Hall Effect thruster to one end for station keeping and keep stacking them like a caterpillar. The next time the Dragonlab flies or if somebody wants to do another station or telescope, the caterpillar can then serve as a ready to use 20-solar array power farm.

Offline LegendCJS

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Re: Dragon trunk reuse/stockpile
« Reply #17 on: 07/13/2012 09:15 pm »
Forget about the ISS using the robotic arm to attach the trunk or its array in a daisy chain. Just have the Dragon (which has its own RCS) depart the station with the trunk attached, fly over to the column of previously flown trunks and docket the trunk with the chain on its own. The dragon then separates and re-enters the atmosphere on its own leaving a stack of trunks and solar arrays in space to serve as a power station for future projects.

Who cares if crap and other waste products from the ISS is burned up in a re-entry or kept on a nearby station in space? It doesn't cost anything to keep it there. Also, who cares if the solar array assembly also happens to carry feces in its trunks? Just attach a Hall Effect thruster to one end for station keeping and keep stacking them like a caterpillar. The next time the Dragonlab flies or if somebody wants to do another station or telescope, the caterpillar can then serve as a ready to use 20-solar array power farm.

You will not have waste moving from pressure to no pressure for the purpose of disposal in any vehicle, even the trunk.  So no worries about having gross kinds of stuff building up in this power farm stack of yours, only cast off unpressurized station components.
Remember: if we want this whole space thing to work out we have to optimize for cost!

Offline douglas100

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Re: Dragon trunk reuse/stockpile
« Reply #18 on: 07/13/2012 10:31 pm »
Just about all the suggestions made so far are probably doable technically and discussing them can be fun. But my first thought is always why do it?

It's natural to want to reuse equipment, but this desire shouldn't override common sense. The ISS doesn't need more solar panels. It doesn't need lots of left over Dragon trunks attached to it. (They would have to be extensively redesigned to be used like that anyway). Compared with the capsule, the trunk is designed to be comparatively cheap and expendable.

I agree with what Lars_J said. There is no reason to do this.
Douglas Clark

Offline dwightlooi

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Re: Dragon trunk reuse/stockpile
« Reply #19 on: 07/13/2012 10:32 pm »
Forget about the ISS using the robotic arm to attach the trunk or its array in a daisy chain. Just have the Dragon (which has its own RCS) depart the station with the trunk attached, fly over to the column of previously flown trunks and docket the trunk with the chain on its own. The dragon then separates and re-enters the atmosphere on its own leaving a stack of trunks and solar arrays in space to serve as a power station for future projects.

Who cares if crap and other waste products from the ISS is burned up in a re-entry or kept on a nearby station in space? It doesn't cost anything to keep it there. Also, who cares if the solar array assembly also happens to carry feces in its trunks? Just attach a Hall Effect thruster to one end for station keeping and keep stacking them like a caterpillar. The next time the Dragonlab flies or if somebody wants to do another station or telescope, the caterpillar can then serve as a ready to use 20-solar array power farm.

You will not have waste moving from pressure to no pressure for the purpose of disposal in any vehicle, even the trunk.  So no worries about having gross kinds of stuff building up in this power farm stack of yours, only cast off unpressurized station components.

The point is that it really doesn't matter if station waste is de-orbited or not. The only reason they are taken off station is so they don't take up space in the station. And, the only reason they are not simply set adrift is because you don't want hundreds of pieces of free floating junk near the station forming a navigational hazard.

Putting them all in trunks and stacking the trunks into a single, larger, manageable, station keeping object is for all intents and purposes as good as de-orbiting them. Each Dragon trunk has 5kW of solar arrays... with 12 missions, that is a total of 60 kW of arrays... that's almost twice that produced by each of the ISS's 32.8 kW solar collector "wings" or about half the ISS's power generation capacity.


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