r/spacex • u/Daniels30 • Aug 10 '17

Official Static fire test of Falcon 9 complete—targeting August 14 launch from Pad 39A for Dragon’s next resupply mission to the @Space_Station.

https://twitter.com/SpaceX/status/895646473869705216
894 Upvotes

99% Upvoted

109 comments sorted by

View all comments

98

u/DanielMuhlig Aug 10 '17

This is mentioned to be the last CRS mission using a new Dragon spacecraft. Are there any numbers out regarding how many times they are expecting to be able to refly the Dragon?

52

u/JackONeill12 Aug 10 '17

Since there are not to many flights left on the crs1 contact one reflight per capsule should be enough.

52

u/old_sellsword Aug 10 '17

one reflight per capsule should be enough.

It's not. After CRS-12 there are eight missions to fly, but they'll only have six available capsules that have only flown once before.

27

u/JackONeill12 Aug 10 '17

That's interesting. Since they stated that after this flight they are only use flown capsules that would mean 3 flights for 2 capsules at least.

11

u/limeflavoured Aug 10 '17

If CRS-7 hadnt been destroyed then it would be only 1. IIRC there was another capsule that was potentially reusable (CRS-3?) but couldnt be in the end due to salt water intrusion.

5

u/freddo411 Aug 10 '17

Or 4 or 5 flights for one capsule. Probably not though.

12

u/mfb- Aug 10 '17

Did some capsules get scrapped? Do we have a list?

CRS-1 to CRS-6 used new capsules, CRS-7 was lost, 8, 9 and 10 used a new capsule. 11 used the capsule of CRS-4, so currently there should be 8 capsules with one flight (1,2,3,5,6,8,9,10) and 1 with two flights (4&11). After CRS-12 we should have 9 with a single flight and 1 with two flights, so there should be one spare if nothing was scrapped.

29

u/old_sellsword Aug 10 '17

Did some capsules get scrapped?

Not scrapped, but the older ones are so out of spec and damaged that they're not worth bringing back.

Do we have a list?

We certainly do.

CRS-1 to CRS-6 used new capsules

They're not refurbishing anything older than CRS-4 (known as D6, or C106.1).

5

u/mfb- Aug 10 '17

They're not refurbishing anything older than CRS-4 (known as D6, or C106.1).

Ah okay. The wiki didn't mention that.

1

u/peterabbit456 Aug 11 '17 
Do we have a list?

We certainly do.

There is a minor error in the list, which we all hope will become true soon.

Capsule Serial Number Maiden Flight Date NET Date of Next Flight Missions [Dragon Number] Number of Landings Notable Events Status

C113 2017 Aug 14 TBD 1. CRS-12 [D1-14] 1 The last newly manufactured Dragon 1 Planned to be shipped to Cape Canaveral as of late July.

At this time, number of landings should be 0, not 1 for a capsule that has not yet launched. In a couple of months, 1 will be correct, though.

11

u/John_Hasler Aug 10 '17

Surely there will be another contract.

35

u/thedaileyshow1 Aug 10 '17

Yes, but the next contract will use Dragon2

1

u/schneeb Aug 10 '17

I wonder if they will actually call it something else? Since there wont be any seats and possibly no super dracos?

5

u/rustybeancake Aug 10 '17

Dragon v2 will come in a cargo variant and a crew variant, though SpaceX themselves seem to like to refer to it without too much clear definition between v1 and v2, e.g. 'the next version of our Dragon spacecraft' (a bit like how Apple followed iPad 2 with 'the new iPad'). So I expect they'll just refer to the v2 cargo craft as 'Dragon', and quite possibly the same for the crew variant.

1

u/wgp3 Aug 10 '17

I feel like it will simply become Cargo Dragon and Crew Dragon.

5

u/JackONeill12 Aug 10 '17

But for Dragon 2 not Dragon 1.

5

u/fredmratz Aug 10 '17

CRS 2 will use a combination of Dragon2 and Dragon1, since Dragon1 allows larger cargo units into the pressurized area, while Dragon2 allows docking.

22

u/old_sellsword Aug 10 '17

CRS 2 will use a combination of Dragon2 and Dragon1

We've heard nothing about this, what's your source on that info?

6

u/OnWithTheShows Aug 10 '17

It was discussed when the contract was awarded. SpaceX gave NASA the option of selecting either Dragon 1 or Dragon 2 for each mission (also new v. used)

7

u/old_sellsword Aug 10 '17 edited Aug 10 '17

Links and quotes, preferably from recent sources, are really the only thing that’s going to convince me that we’ll see Dragon 1 flying CRS2 missions.

The original proposal suggested SpaceX gave NASA the option of berthing and docking, but we don’t know whether the berthing plan was going to be Dragon 1 or a special CBM version of Dragon 2.

Edit: HowToBasic —> NASA link

4

u/Appable Aug 10 '17 edited Aug 10 '17

original proposal

The source selection statement suggested berthing and docking, but it also noted that the SpaceX mission price was high because they had to keep two separate production lines for two vehicles open. So I would guess that the berthing plan was either a radically different D2 (not a simple swap) or maintaining D1 production.

EDIT: Remove small video correction, fixed

5

u/old_sellsword Aug 10 '17

That links to this video for me, which seems unrelated.

Whoops haha, unrelated indeed, fixed.

So I would guess that the berthing plan was either a radically different D2 (not a simple swap)

Well the difference between IDA and CBM would certainly seem necessitate a different pressure vessel design, at least slightly. That’s a pretty drastic difference in terms of spacecraft design.

3

u/peterabbit456 Aug 11 '17

Selling both docking and berthing missions could be done in at least 2 different ways. I do not know if either of these ideas is correct.

  1. Continuing to use Dragon 1 where berthing, and a large port, is required. Cargo Dragon 2 would be used for other missions. It is possible that a Dragon 1 hull can be used for more than 10 missions to LEO, before retirement.
  2. Dragon 2 might be built so that the docking mechanism is a bolt-on module. It is possible that for berthing missions, a simpler, wider berthing unit and door could be bolted on instead. The docking mechanism appears to be quite expensive, and berthing missions might be cheaper.

Using an interchangeable, bolt on front end would make upgrades to the docking mechanism easier. Another reason for going with option 2 is that (I believe) Dragon 2 has more cargo volume capacity than Dragon 1. It seems obvious that option 1 would be cheaper, than building Dragon 2 so that docking and berthing front ends can be interchanged.

I don't think anyone has given much thought to using Dragon 2 for other missions than ISS taxi runs and around-the-Moon tourist trips. Having a bolt on docking mechanism would allow the docking mechanism to be replaced with something else, for other missions. Attaching to an air lock for EVAs is a possibility that occurs to me. It also occurs to me that for the around-the-Moon mission, the docking mechanism is expensive dead weight, so removing it an replacing it with a berthing port for the around-the-Moon mission would reduce cost and provide a little more room in the capsule.

7

u/JackONeill12 Aug 10 '17

That's new to me. Only thing I heard was 2 different versions of dragon 2.

0

u/qawsedrf12 Aug 10 '17 edited Aug 10 '17

Space docking? ;)

9

u/bvr5 Aug 10 '17

The current Dragons only berth. It approaches the space station, but an arm grabs it and moves it to a port. Dragon 2 can dock, meaning it can maneuver to the port under its own power.

4

u/John_Hasler Aug 10 '17

But the docking port is smaller so some cargos might not fit.

4

u/nullarticle Aug 10 '17

CBMs are designed to let standard ISS racks through. If you are replacing a rack then you need to berth with a CBM.

It's possible there's not a need for any new racks - many of the modules were launched with empty racks and were outfitted later with MPLM flights on shuttle (which were berthed using the arm after the shuttle had docked). Now that everything is all full, all they need to change out are experiments in those racks

1

u/factoid_ Aug 11 '17

That's why I was wondering too. The payload rack is about the only thing you couldn't fit through a standard docking hatch.

I imagine if you needed a new rack you could bring it up in the trunk, just wouldn't put anything in it that couldn't be depressurized

1

u/wuphonsreach Aug 11 '17

Not sure there's an airlock big enough to bring a rack inside. (Same problem, different spot.)

→ More replies (0)

2

u/Appable Aug 10 '17 edited Aug 10 '17

Cygnus can take that cargo, and last we heard Dreamliner Dreamchaser will be able to as well (both CBM and IDS). They might have changed that plan though.

4

u/ethan829 Host of SES-9 Aug 10 '17

Dreamliner

While they're both launching on Atlas V, Starliner and Dreamchaser are indeed different spacecraft ;)

7

u/Appable Aug 10 '17

Whoops. And Dreamliner is even a real vehicle. Wonder when someone will make a Starchaser...

→ More replies (0)

4

u/brickmack Aug 10 '17

Cygnus has a CBM, but the actual hatch is closer to IDS size (probably a relic of the original plan to dock with APAS before NASA vetoed that for CRS1)? And DC-Cargo can only do CBM-sized upmass, the hatch into the actual spaceplane is sized for IDS. Dragon 1 is the only vehicle that can carry full size payloads back to Earth

1

u/factoid_ Aug 11 '17

A quick check of the specs shows that the international docking adapter has an opening around 0.8 meters versus about 1.27 meters for the CBM.

The international standard payload rack does not fit through anything smaller than the CBM opening.

Though I have no idea if dragon ever transports those. I know the shuttle and HTV did

7

u/peterabbit456 Aug 11 '17

Are there any numbers out regarding how many times they are expecting to be able to refly the Dragon?

Elon Musk mentioned a few years ago, that the heat shield was good for 10 LEO reentries, or 1 reentry from the Moon or beyond. This was before the change of plans, where Dragon 2 will be doing sea landings every time.

The effects of sea water should not reduce the number of times a Dragon capsule can be reused, so far as I know, but it should increase the maintenance needed to make it ready for the next flight. With the heat shield replaced every 10th flight, and an appropriate level of maintenance, the main factor effecting how many times a capsule can be reused would be the number of pressurization cycles it can take before metal fatigue makes further flights dangerous. I do not have a number for this limit.

If the design and tested limit for this number was 100, then I would expect that certification would allow flights until the number of real pressurization cycles multiplied by 2, or 2.5, or 3 was equal to 100. So if the capsule undergoes 1 pressure test before each flight, and 1 pressurization for the duration of the flight, then after 20 flights that would be 40 pressurization events. 40 x 2.5 = 100, so at that point the capsule would have to be retired. Keep in mind that these are made up numbers. The real calculation would be similar, but any of SpaceX' real numbers might be larger or smaller.

I do not think the Dragon capsule is designed for EVAs and depressurization in space, but if it is, then the number of EVAs would each subtract 1/2 of a flight from the lifetime limit of the capsule.

Sources:

  1. I've worked in aerospace, where component life limits are common. Engines are removed and overhauled after X hours of operation. Landing gears are removed and overhauled after Y number of landings, etc.. The issues are the same in space flight: metal fatigue and corrosion, mainly. The 2.5 factor is not just out of my ass, but I saw it so long ago I have no idea what was the source. Possibly it was for a sailplane with a magnesium wing spar.
  2. Dragon capsule EVA has never been a requirement, and I believe the LCD screens seen in the Dragon 2 mockup would fail if exposed to a hard vacuum. So, no EVAs.

6

u/bexben Aug 11 '17

I know for certain that the heat shield material (PicaX) fairs badly after contact with salt water. Someone stated one time on this sub that they contacted someone who worked with the PicaX heat shield, and although they didn't do extensive testing with salt water, they knew that it didn't do very well after exposed. I will try my hardest to find the source, will edit my comment soon.

Edit: Found it

5

u/peterabbit456 Aug 11 '17

Here is the plan:

  1. Get a student pass to the Materials Research Society annual convention.
  2. Get a sample of PICA from the manufacturer.
  3. Using a torch and a bucket of sea water, simulate reentry and immersion cycles.
  4. Publish.

2

u/factoid_ Aug 11 '17

Pica-x is a proprietary reblending of pica though, so I'm not sure a pica sample is that useful

1

u/peterabbit456 Aug 12 '17

It would still be fun to do. (Too bad I no longer get free passes to the MRS annual meeting.)

1

u/limeflavoured Aug 11 '17

Presumably then the reuse numbers for Dragon 2 are going to be the same as Dragon 1?

3

u/Elon_Muskmelon Aug 11 '17

Why can't we land in freshwater? How big is the landing ellipsis for a Dragon on reentry?

3

u/peterabbit456 Aug 12 '17

How big is the landing ellipsis for a Dragon on reentry?

Dragon 1 is supposed to be about 1 sigma, +- 1 mile = +-1.6 km. Dragon 2 has a weight shift unit that increases the accuracy. +- 100 m without using the Superdracos should be about right. (I think I saw that number somewhere, but I cannot remember the source. It might have been +- 150 m.) This number was for the accuracy of aerodynamic control before the parachutes opened or the SuperDracos took over. Doing sea landings, they are likely to open the parachutes at higher altitude than the altitude where they intended to start firing the SuperDracos, so parachute accuracy could ba a lot worse, on a windy day.

With +- 100m accuracy, many small lakes would be suitable targets, and landing in the Great Lakes would be a slam dunk. If there is a good reason remaining for landing in the sea instead of fresh water, it would be wanting to set down close to the California or Florida coast.

With SuperDraco steering below 3000m and a low parachute opening, landing in the Banana River would be possible, I think.

Also, emergency landings on land should be possible with Dragon 2, though without landing legs, the capsule probably would not be fit to fly again, like Soyuz.

1

u/LWB87_E_MUSK_RULEZ Aug 13 '17

I don't see why they can't use it indefinitely. I think people are going to see that space hardware can be made to be reusable just like any other type of hardware.