SpaceX Dragon 2 Updates and Discussion - Thread 3

[gongora]

From what I recall from past press conferences, the first 2 crewed Dragon2 flights will be new. After that, it hasn't yet been determined.

The contract calls for all new vehicles.  They could possibly negotiate a change later.

[garcianc]

My fifteen minutes of searching are up with no links to share, but I recall seeing something about Bigelow reserving four crew launches from SpaceX sometime within the last six months.  My memory might be off on the details so all stop there.  What is really important here is that NASA isn't necessarily the only customer for crew Dragon.

Although it sounds like it is not necessarily critical to your point, here is the link to a story regarding the Bigelow-SpaceX launches: https://www.space.com/bigelow-spacex-tourist-flights-space-station.html

[yg1968]

From what I recall from past press conferences, the first 2 crewed Dragon2 flights will be new. After that, it hasn't yet been determined.

The contract calls for all new vehicles.  They could possibly negotiate a change later.

Yes I know but I believe that NASA is open to reuse but it would require further work for certification of the reused crewed Dragon2.

[Joseph Peterson]

My fifteen minutes of searching are up with no links to share, but I recall seeing something about Bigelow reserving four crew launches from SpaceX sometime within the last six months.  My memory might be off on the details so all stop there.  What is really important here is that NASA isn't necessarily the only customer for crew Dragon.

Although it sounds like it is not necessarily critical to your point, here is the link to a story regarding the Bigelow-SpaceX launches: https://www.space.com/bigelow-spacex-tourist-flights-space-station.html

Finding the link that states Bigelow has reserved up to four(not definitely four though) flights supports my point.  Thank you for tracking that down.

[First Mate Rummey]

SpaceX launches Dragon as it prepares for next cargo contract
https://spacenews.com/spacex-launches-dragon-as-it-prepares-for-next-cargo-contract/

The next two missions will mark the end of SpaceX’s original Commercial Resupply Services (CRS) contract with NASA to transport cargo to and from the ISS, awarded in 2008. SpaceX will then transition to a follow-on contract, CRS2, with the first mission under that contract planned for the third quarter of 2020, Jensen said.
The change in contract will also mark a shift in vehicles, with SpaceX retiring the original Dragon in favor of Dragon 2, a version of the Crew Dragon spacecraft the company has been developing for NASA’s commercial crew program...

[theonlyspace]

So this means Cargo Dragon 2 will dock using a  ISS docking port  and not be berthed using the Canadarm2.  This will result in smaller size payloads  only will be able to be offloaded into the station . The docking ports are considerable smaller diameter than the berthing ports now used

[woods170]

So this means Cargo Dragon 2 will dock using a  ISS docking port  and not be berthed using the Canadarm2.  This will result in smaller size payloads  only will be able to be offloaded into the station . The docking ports are considerable smaller diameter than the berthing ports now used

In practice the average size of pressurized payload won't be smaller. Almost no cargo brought up - to date - to ISS on cargo Dragon required the CBM-sized passage way.

[Hog]

[Mike_1179]

In practice the average size of pressurized payload won't be smaller. Almost no cargo brought up - to date - to ISS on cargo Dragon required the CBM-sized passage way.

CBMs are sized to allow ISS racks (International Standard Payload Rack) to fit through. Made a lot of sense during construction / fit out of ISS when you could park a MPLM on one and get a crew quarters or other full-size rack in one shot.

Do we know if Dragon has carried any ISPRs up to ISS? i don't remember reading about any on a manifest

[eeergo]

In practice the average size of pressurized payload won't be smaller. Almost no cargo brought up - to date - to ISS on cargo Dragon required the CBM-sized passage way.

CBMs are sized to allow ISS racks (International Standard Payload Rack) to fit through. Made a lot of sense during construction / fit out of ISS when you could park a MPLM on one and get a crew quarters or other full-size rack in one shot.

Do we know if Dragon has carried any ISPRs up to ISS? i don't remember reading about any on a manifest

Dragon cannot carry ISPRs because of lack of internal space, even though the hatch would allow one to pass:
https://forum.nasaspaceflight.com/index.php?topic=28006.msg894330#msg894330
Same goes for Cygnus: https://www.nasaspaceflight.com/2015/08/htv-5-iss-berthing/

On the other hand, HTV has (most recently in HTV-7 - in fact, if I'm not mistaken, it was the first time new full-fledged ISPRs were transferred to the Station by a VV since STS times).

[woods170]

In practice the average size of pressurized payload won't be smaller. Almost no cargo brought up - to date - to ISS on cargo Dragon required the CBM-sized passage way.

CBMs are sized to allow ISS racks (International Standard Payload Rack) to fit through. Made a lot of sense during construction / fit out of ISS when you could park a MPLM on one and get a crew quarters or other full-size rack in one shot.

Do we know if Dragon has carried any ISPRs up to ISS? i don't remember reading about any on a manifest

Dragon cannot carry ISPRs because of lack of internal space, even though the hatch would allow one to pass:
https://forum.nasaspaceflight.com/index.php?topic=28006.msg894330#msg894330
Same goes for Cygnus: https://www.nasaspaceflight.com/2015/08/htv-5-iss-berthing/

On the other hand, HTV has (most recently in HTV-7 - in fact, if I'm not mistaken, it was the first time new full-fledged ISPRs were transferred to the Station by a VV since STS times).

Minor nit: although Cygnus is berthed on a CBM the hatch in Cygnus is not a full-size CBM hatch. It is smaller and does not allow for transfer of ISPRs.

[First Mate Rummey]

SpaceX to begin flights under new cargo resupply contract next year
https://spaceflightnow.com/2019/08/02/spacex-to-begin-flights-under-new-cargo-resupply-contract-next-year/

The Dragon 2 spacecraft will be capable of delivering up to 7,290 pounds (3,307 kilograms) of cargo to the space station, including pressurized and unpressurized equipment, according to the NASA inspector general.

But the Dragon 2’s primary arrival mode, using docking rather than capture and berthing with the robotic arm, comes with a limitation.

The hatches through the space station’s docking ports are narrower than the passageways through the berthing ports currently used by Dragon cargo vehicles.

“The docking configuration for Dragon 2 has limitations regarding the size of the hatch such that larger items including spacesuits and large cargo bags cannot fit,” the NASA inspector general said.

[Joffan]

SpaceX to begin flights under new cargo resupply contract next year
https://spaceflightnow.com/2019/08/02/spacex-to-begin-flights-under-new-cargo-resupply-contract-next-year/

The Dragon 2 spacecraft will be capable of delivering up to 7,290 pounds (3,307 kilograms) of cargo to the space station, including pressurized and unpressurized equipment, according to the NASA inspector general.

But the Dragon 2’s primary arrival mode, using docking rather than capture and berthing with the robotic arm, comes with a limitation.

The hatches through the space station’s docking ports are narrower than the passageways through the berthing ports currently used by Dragon cargo vehicles.

“The docking configuration for Dragon 2 has limitations regarding the size of the hatch such that larger items including spacesuits and large cargo bags cannot fit,” the NASA inspector general said.

The NASA IG has the shoe on the wrong foot. The docking hatch for the ISS has the limitations he refers to; the Dragon 2 merely conforms to those.

I wouldn't be surprised if SpaceX could develop the capability to dock to the port they have previously berthed to with the existing cargo Dragon, if they were asked to do so. It's mostly a precision control issue.

[First Mate Rummey]

So, what are the improvements of Cargo Dragon 2 vs. Dragon 1?
- Reusable 5 times rather than 3.
- Better water isolation (still implied in the higher reusability)?
- Commonality with Crew Dragon (but I fail to see this as an advantage since D1 is a mature product by now).

And the disadvantages?
- Higher risk due to a new vehicle.
- Can transfer smaller cargo objects.
- Only 3.300 kg of Cargo to ISS, vs. 6.000 of D1 (according to https://www.spacex.com/dragon ).


Other?

[gongora]

Slightly larger pressurized volume.
Nominally lands a little closer to shore and close to KSC.

[gongora]

The 6000kg theoretical cargo upmass for Dragon 1 would never be reached with a real CRS payload.  I have doubts about the accuracy of the 3300kg number but even if it's accurate it would probably be fine.

[soltasto]

- Only 3.300 kg of Cargo to ISS, vs. 6.000 of D1 (according to https://www.spacex.com/dragon ).

I assume you have taken the 3300kg figure from the OIG report and that seems a like a valid source, but the numbers on https://www.spacex.com/dragon seems also to be about Dragon 2. Don't really know who of the two is right. Maybe someone can ask SpaceX directly?

[DistantTemple]

So, what are the improvements of Cargo Dragon 2 vs. Dragon 1?
- Reusable 5 times rather than 3.
- Better water isolation (still implied in the higher reusability)?
- Commonality with Crew Dragon (but I fail to see this as an advantage since D1 is a mature product by now).

And the disadvantages?
- Higher risk due to a new vehicle.
- Can transfer smaller cargo objects.
- Only 3.300 kg of Cargo to ISS, vs. 6.000 of D1 (according to https://www.spacex.com/dragon ).


Other?

Commonality between crew and cargo D2s mean the pressure vessel and many other systems use the same production line. That saves space, keeps frequency up and production staff memories good!

[First Mate Rummey]

But for the 6 planned CRS-2 missions, they should already have enough reused D1 available, so no actual need for using a new craft.

[abaddon]

Automated docking versus manual berthing is an advantage.