SpaceX Dragon 2 Updates and Discussion - Thread 3

[whitelancer64]

Can the Super Dracos still throttle, now that there are burst disks instead of valves?

[EspenU]

Can the Super Dracos still throttle, now that there are burst disks instead of valves?

Yes. The replaced valve was not for throttle control.

[Alexphysics]

Can the Super Dracos still throttle, now that there are burst disks instead of valves?

The burst disks are on the pressurization system not propellant system. They obviously can and they must be able to throttle them up and down, otherwise they wouldn't be able to steer the Crew Dragon away from the rocket

[FattyLumpkin]

Can anyone one tell me what the total mass for a Crew Dragon parachute is?   thnx  FL

[Norm38]

Have we seen a Cargo Dragon2 yet?  Flight for CRS-21 is coming up in 3 months.
Does it have windows?

Also very cool to hear that Capsule Endeavor will fly again so soon on Crew-2.  I wonder how big the Nasa Dragon roost will be?  Maybe only 4 capsules, same as the 4 shuttles.  That would be an interesting parallel.

[whitelancer64]

Can anyone one tell me what the total mass for a Crew Dragon parachute is?   thnx  FL

I suppose that would be SpaceX proprietary information, but the main parachutes for Orion are the same size - 116 ft in diameter - and are 310 lb each. Orion's drogue chutes are 23 ft in diameter and 80 lb each.

https://www.nasa.gov/sites/default/files/atoms/files/orion_parachutes.pdf

[kdhilliard]

Have we seen a Cargo Dragon2 yet?  Flight for CRS-21 is coming up in 3 months.
...

Do we even know if Cargo Dragon flights will RTLS?  Might they land ASDS due to either increased mass or the desire to fly the same profile as crew flights for some strange reason such as maintaining proficiency and gathering data?

[AndrewRG10]

Regarding the discussion of trunk separation timing in the DM-2 thread.

We know the trunk separates before de-orbit burn. I know some are saying thruster failure is LOC anyway, but I can't help but think back to Soyuz TM-5. When they used to jettison the orbital module before deorbit burn. The de-orbit burn failed so thus they waited 24 hours in the descent module with no toilet. And also remember CRS-2 where they had thruster failure but did fix it.

What if something like CRS-2 and TM-5 combined happens where they jettison the trunk but encounter thruster issues and they have to wait 24 hours for the next opportunity but they do fix the issue. Yes, they still have the toilet and living space unlike TM-5, but does Dragon have enough power for 24 hours for the next opportunity and can it stay cool enough without radiators for 24 hours?

[niwax]

Regarding the discussion of trunk separation timing in the DM-2 thread.

We know the trunk separates before de-orbit burn. I know some are saying thruster failure is LOC anyway, but I can't help but think back to Soyuz TM-5. When they used to jettison the orbital module before deorbit burn. The de-orbit burn failed so thus they waited 24 hours in the descent module with no toilet. And also remember CRS-2 where they had thruster failure but did fix it.

What if something like CRS-2 and TM-5 combined happens where they jettison the trunk but encounter thruster issues and they have to wait 24 hours for the next opportunity but they do fix the issue. Yes, they still have the toilet and living space unlike TM-5, but does Dragon have enough power for 24 hours for the next opportunity and can it stay cool enough without radiators for 24 hours?

Could they use one of their abort sites for an emergency landing so they don't have to wait the full day? For example, they can support a crewed abort near Ireland. The procedure for recovery shouldn't be too different from a (somewhat) nominal landing, although they might sacrifice the capsule if they can't put it on a ship.

[Alexphysics]

Regarding the discussion of trunk separation timing in the DM-2 thread.

We know the trunk separates before de-orbit burn. I know some are saying thruster failure is LOC anyway, but I can't help but think back to Soyuz TM-5. When they used to jettison the orbital module before deorbit burn. The de-orbit burn failed so thus they waited 24 hours in the descent module with no toilet. And also remember CRS-2 where they had thruster failure but did fix it.

What if something like CRS-2 and TM-5 combined happens where they jettison the trunk but encounter thruster issues and they have to wait 24 hours for the next opportunity but they do fix the issue. Yes, they still have the toilet and living space unlike TM-5, but does Dragon have enough power for 24 hours for the next opportunity and can it stay cool enough without radiators for 24 hours?

If I'm not mistake wrt power, woods once said Dragon wouldn't even need the solar panels for the way to the ISS because its own batteries can last well over two days or something like that (don't remember exactly sorry) so my worry would be more on the radiator side. It would still be survivable I think, just not comfortable for sure

[Lars-J]

We know the trunk separates before de-orbit burn.

Do we actually know that? I may be wrong, but I had assumed that the trunk would be separated after the de-orbit burn.

[ShSch]

We know the trunk separates before de-orbit burn.

Do we actually know that? I may be wrong, but I had assumed that the trunk would be separated after the de-orbit burn.

The capsule jettisoned its rear trunk at 7:48 a.m. EST (1248 GMT), leaving the power module behind in orbit as the crew return craft ignited its Draco thrusters again at 7:52 a.m. EST (1252 GMT) for a 15-minute, 25-second braking burn.

From here: https://spaceflightnow.com/2019/03/08/spacex-crew-capsule-returns-to-earth-paving-the-way-for-human-launches/

[Alexphysics]

We know the trunk separates before de-orbit burn.

Do we actually know that? I may be wrong, but I had assumed that the trunk would be separated after the de-orbit burn.

We saw it during Demo-1, the trunk from that mission is still up there and plans haven't changed since then per the timeline put out by NASA for Demo-2. We knew it even before Demo-1 from some of the FAA permits or studies or whatever it was, but I remember knowing about it sometime in 2018 in an FAA file saying that the trunk would separate before deorbit burn.

[Tulse]

What is the reason for not separating the trunk after de-orbit? I would have thought disposing of the trunk would be good practice, rather than leaving it as debris.

[whitelancer64]

What is the reason for not separating the trunk after de-orbit? I would have thought disposing of the trunk would be good practice, rather than leaving it as debris.

I presume it would be to eliminate the risk of re-contact of the capsule and the trunk.

[Lars-J]

We know the trunk separates before de-orbit burn.

Do we actually know that? I may be wrong, but I had assumed that the trunk would be separated after the de-orbit burn.

We saw it during Demo-1, the trunk from that mission is still up there and plans haven't changed since then per the timeline put out by NASA for Demo-2. We knew it even before Demo-1 from some of the FAA permits or studies or whatever it was, but I remember knowing about it sometime in 2018 in an FAA file saying that the trunk would separate before deorbit burn.

D'oh! Of course, I stand corrected.

[rsdavis9]

Lower fuel usage to deorbit just the reentry capsule?
The trunk ways something.

[Mandella]

Also if there is an issue with detaching the trunk it allows time to troubleshoot, as opposed to only being minutes from atmosphere.

[Comga]

What is the reason for not separating the trunk after de-orbit? I would have thought disposing of the trunk would be good practice, rather than leaving it as debris.

This has been EXTENSIVELY discussed, up-thread and elsewhere, in many posts. If you read thru you will understand the issues without repeating the question.
As to the trunk being orbital debris, the ISS is flown low, around 400 km altitude, partly so that the exosphere scrubs debris out of orbit.  The ISS requires frequent boosting to keep it from being dragged down.  (Check out the ISS altitude vs time graph on Heavens Above.)  The trunk is low density, quite hollow , so will have a relatively short lifetime at an altitude with few satellites.

[Alexphysics]

What is the reason for not separating the trunk after de-orbit? I would have thought disposing of the trunk would be good practice, rather than leaving it as debris.

This has been EXTENSIVELY discussed, up-thread and elsewhere, in many posts. If you read thru you will understand the issues without repeating the question.
As to the trunk being orbital debris, the ISS is flown low, around 400 km altitude, partly so that the exosphere scrubs debris out of orbit.  The ISS requires frequent boosting to keep it from being dragged down.  (Check out the ISS altitude vs time graph on Heavens Above.)  The trunk is low density, quite hollow , so will have a relatively short lifetime at an altitude with few satellites.

Well not that I would call "more than a year and a half" a "short lifetime" in orbit. The trunk from Demo-1 is still up there and hasn't really gone down too much. It may still take another year until it decays and reenters