SpaceX Falcon 9 / Dragon 2 : SpX-DM1 : March 2, 2019 : DISCUSSION

[spacebleachers]

Its going vertical now!

[envy887]

I feel like I’m missing something. How does having Dragon mated to F9 help certify F9’s fueling procedures? Unless it’s having the abort system fueled and armed?

It shows confidence that the (human rated) booster won't blow up.

Is the NASA cargo for DM-1 packed in the Crew Dragon already?

If not, then there is no customer payload on the vehicle, and so no point in demating for the static fire.

[jpo234]

I feel like I’m missing something. How does having Dragon mated to F9 help certify F9’s fueling procedures? Unless it’s having the abort system fueled and armed?

It shows confidence that the (human rated) booster won't blow up.

Is the NASA cargo for DM-1 packed in the Crew Dragon already?

If not, then there is no customer payload on the vehicle, and so no point in demating for the static fire.

What is the planned NASA cargo? Just "tang and t-shirts"?

[TGMetsFan98]

I feel like I’m missing something. How does having Dragon mated to F9 help certify F9’s fueling procedures? Unless it’s having the abort system fueled and armed?

It shows confidence that the (human rated) booster won't blow up.

Is the NASA cargo for DM-1 packed in the Crew Dragon already?

If not, then there is no customer payload on the vehicle, and so no point in demating for the static fire.

Except the risk of damaging Dragon itself...

Obviously no one expects F9 to have an issue. But there’s a reason they’ve been conducting static fires without payloads mated. “Showing confidence” by firing with payload on board is no different for Dragon than any other payload.

[Johnnyhinbos]

I feel like I’m missing something. How does having Dragon mated to F9 help certify F9’s fueling procedures? Unless it’s having the abort system fueled and armed?

It shows confidence that the (human rated) booster won't blow up.

Is the NASA cargo for DM-1 packed in the Crew Dragon already?

If not, then there is no customer payload on the vehicle, and so no point in demating for the static fire.

Except the risk of damaging Dragon itself...

Obviously no one expects F9 to have an issue. But there’s a reason they’ve been conducting static fires without payloads mated. “Showing confidence” by firing with payload on board is no different for Dragon than any other payload.

Well - you see, you're putting humans on this thing - during fueling. And SpaceX has fought to establish this protocol. That means that SpaceX is 100% confident that this thing is safe for humans (well, within the NASA human safety requirements). By not having a full stack for a static fire is saying exactly the opposite of that. Now - I would add the one caveat that there is an abort system to save the crew during a catastrophic failure. I'd be curious to know if they arm this system during a static fire to save the capsule. Chris G - perhaps you could slip in that question during the NASA press conference I can only assume there will be around the launch date...?   

[kdhilliard]

afety requirements). ... there is an abort system to save the crew during a catastrophic failure.  I'd be curious to know if they arm this system during a static fire to save the capsule.

If the abort system is to be armed, are there additional range restrictions ensuring boat traffic is clear of potential landing areas?

[envy887]

I feel like I’m missing something. How does having Dragon mated to F9 help certify F9’s fueling procedures? Unless it’s having the abort system fueled and armed?

It shows confidence that the (human rated) booster won't blow up.

Is the NASA cargo for DM-1 packed in the Crew Dragon already?

If not, then there is no customer payload on the vehicle, and so no point in demating for the static fire.

Except the risk of damaging Dragon itself...

Obviously no one expects F9 to have an issue. But there’s a reason they’ve been conducting static fires without payloads mated. “Showing confidence” by firing with payload on board is no different for Dragon than any other payload.

Yes, and that reason is that those payloads are not SpaceX's to risk unnecessarily during a SF. This Dragon and everything in it belongs to SpaceX (assuming it hasn't been loaded), so if they have a need to keep it on top for a SF then they can do that.

If the F9 has a problem, losing the Dragon would be a minor worry compared to RTF for Falcon and rebuilding 39A. The next Dragon in line will be ready in a couple months, long before the pad would be ready and probably well before Falcon could RTF on 40.

[mjcrsmith]

It will be interesting to watch the access arm movements if any for the SF. 

[Joffan]

It will be interesting to watch the access arm movements if any for the SF. 

It would be seriously impressive to extend this static fire to include a full-up launch rehearsal. Board the astronauts, arm the Dragon abort, run the fuel loading and stop at T-zero (that is, after ignition). Then disembark the astronauts, recycle the countdown and run the full static fire - that's the only part of the process that would never have a crew present.

There might well be technical reasons why this is difficult or impossible as simply stated, so take this as a concept to vary for as much experience gathering as possible.

[CorvusCorax]

It will be interesting to watch the access arm movements if any for the SF. 

It would be seriously impressive to extend this static fire to include a full-up launch rehearsal. Board the astronauts, arm the Dragon abort, run the fuel loading and stop at T-zero (that is, after ignition). Then disembark the astronauts, recycle the countdown and run the full static fire - that's the only part of the process that would never have a crew present.

There might well be technical reasons why this is difficult or impossible as simply stated, so take this as a concept to vary for as much experience gathering as possible.

I think you are under a slight misconception regarding what a static fire is

With SpaceX, a static fire always is a full mission dress rehearsal -- up to (but not including) the point of launch clamp release.

Fit check:   <-- you only put stuff on the pad and see if everything fits. No countdown
Dry dress rehearsal: <-- you put stuff on the pad in a countdown sequence and pretend to launch, but you do not add propellant. Sometimes includes mock scrubs/countdown delays
Wet dress rehearsal: <-- You go through a complete countdown until (but not including) ignition. Then you abort the countdown and detank. Sometimes includes mock scrubs/countdown delays.
SpaceX Static fire: <-- Like wet dress rehearsal including ignition of engines and ramping up to full thrust. Abort just before launch clamp release.

Mission dress rehearsal: <-- You do a countdown (usually dry), "pretend to launch" and continue the rehearsal as if, with simulated or mock data (and malfunctions). Important for getting the team routine for complex missions. I think the GPSIII launch did that. You don't necessarily need more than a paper rocket for that one though.


As such whenever SpaceX has done a static fire, they have gone through the full launch procedure. To have that fully realistic, this would include fluids for Dragon and armed abort system, unless they deliberately decide to not include that. Cause even in the worst case scenario, they'd get a free full realism test of the abort system with very valuable data.
Whether or not they can refurbish the dragon after an abort+splash plays a minor role. Its the data which is much more valuable should such a thing happen, and the increased confidence in the abort system it would give everyone.

Edit: Also arming the abort system would include the abort systems self checks and arming procedure in the dress rehearsal, which, if something goes wrong, you don't want to find out on launch day.

Edit of Edit: I missed the part where you suggested putting crew on. This is an uncrewed launch, so not this time, but they could put dummies on to pretend to have a crew. And yes, it would make sense to have that part of the dress rehearsal too. Might actually be.

[Joffan]

(...nice description of various rehearsal levels...)

Edit of Edit: I missed the part where you suggested putting crew on. This is an uncrewed launch, so not this time, but they could put dummies on to pretend to have a crew. And yes, it would make sense to have that part of the dress rehearsal too. Might actually be.

Yes... the main point of my comment - if this wasn't sufficiently clear - was to include crew.

Although this isn't a crewed mission, it is a rehearsal for a crewed mission. They presumably won't rehearse crew boarding for the actual launch of DM-1, so this seemed like a good opportunity. A possible objection from the NASA side could be their aversion to insufficiently demonstrated COPV loading.

[kdhilliard]

It would be seriously impressive to extend this static fire to include a full-up launch rehearsal. Board the astronauts, arm the Dragon abort, run the fuel loading and stop at T-zero (that is, after ignition). Then disembark the astronauts, recycle the countdown and run the full static fire - that's the only part of the process that would never have a crew present.

Did you mean before ignition?

Your proposal seems to combine the worst aspects of load-and-go and early-fueling.

* Crew onboard during fueling, though protected to some degree by an armed capsule abort system.
* Abort system then disarmed allowing support personnel to arrive, disembark crew, and clear pad, working next to a fully fueled vehicle.
* A long pause to allow sub-cooled propellants time to warm up.

What's not to hate?

[Alexphysics]

Worth noting something that a few people are forgetting about the discussion, RP-1 and LOX loading is the same for every Falcon 9 mission now however helium loading changes for crewed missions. The COPV's are loaded 2 hours before launch, then the crew will board inside the capsule and then at T-35minutes the normal propellant loading sequence will begin

[AbuSimbel]

Not to mention that the pad egress system isn't functional as of today. (Or at least I still don't see the wires for the baskets installed in today's photos)

[russianhalo117]

Not to mention that the pad egress system isn't functional as of today. (Or at least I still don't see the wires for the baskets installed in today's photos)

Wires are on site but not installed. It doesn't take long to install them. They are not needed for DM-1.

[Comga]

Worth noting something that a few people are forgetting about the discussion, RP-1 and LOX loading is the same for every Falcon 9 mission now however helium loading changes for crewed missions. The COPV's are loaded 2 hours before launch, then the crew will board inside the capsule and then at T-35minutes the normal propellant loading sequence will begin

That does not seem possible.
The He COPV's are inside the LOX tank so that they can load more He as it gets to cryogenic temperatures. 
They can only put in a fraction of the flight He load at ambient temperature.
We can assume that SpaceX will bring the He COPVs to full pressure before the astronauts board.
Then, as the LOX is loaded, the He pressure will drop, and they will continue to add He to maintain the flight pressure.
That should avoid the stretching that contributed to the AMOS-6 static fire failure.

[Alexphysics]

Worth noting something that a few people are forgetting about the discussion, RP-1 and LOX loading is the same for every Falcon 9 mission now however helium loading changes for crewed missions. The COPV's are loaded 2 hours before launch, then the crew will board inside the capsule and then at T-35minutes the normal propellant loading sequence will begin

That does not seem possible.
The He COPV's are inside the LOX tank so that they can load more He as it gets to cryogenic temperatures. 
They can only put in a fraction of the flight He load at ambient temperature.
We can assume that SpaceX will bring the He COPVs to full pressure before the astronauts board.
Then, as the LOX is loaded, the He pressure will drop, and they will continue to add He to maintain the flight pressure.
That should avoid the stretching that contributed to the AMOS-6 static fire failure.

What you said does not invalidate my comment just extends it further to add the obvious effect that the cold temperatures of the LOX will have. NASA has already explained why there's an initial loading and it's precisely for the reasons you say. Anyways, I would expect the ones on the RP-1 tanks to be almost at flight levels before astronauts board the capsule. Those remain at practically room temperature all the time (yeah, I know, RP-1 is also cooled down too but the temperature difference is not really that high as compared to the LOX).

[whitelancer64]

It will be interesting to watch the access arm movements if any for the SF.

Cross post:

https://forum.nasaspaceflight.com/index.php?topic=47095.msg1904177#msg1904177

Crew access arm has been extended to the Dragon.

[Joffan]

It would be seriously impressive to extend this static fire to include a full-up launch rehearsal. Board the astronauts, arm the Dragon abort, run the fuel loading and stop at T-zero (that is, after ignition). Then disembark the astronauts, recycle the countdown and run the full static fire - that's the only part of the process that would never have a crew present.

There might well be technical reasons why this is difficult or impossible as simply stated, so take this as a concept to vary for as much experience gathering as possible.

Did you mean before ignition?

Your proposal seems to combine the worst aspects of load-and-go and early-fueling.

* Crew onboard during fueling, though protected to some degree by an armed capsule abort system.
* Abort system then disarmed allowing support personnel to arrive, disembark crew, and clear pad, working next to a fully fueled vehicle.
* A long pause to allow sub-cooled propellants time to warm up.

No, T-zero is after ignition, which occurs 2-3 seconds earlier. We have seen countdown aborts after ignition before.

Crew onboard during fueling is how the mission will go. And yes, the capsule abort system is their protection from serious incidents in that phase.

I did not propose - in this scenario - that support personnel should approach a fully-fueled vehicle. There are other, lower-risk ways to handle that - probably the safest is detanking, but SpaceX will have to have acceptably safe processes for handling a T-0 abort.

Recycling countdown with propellants needing re-cooling is definitely one of the processes that SpaceX supports. However this may not even be necessary for a static fire.

No doubt some people would see such a rehearsal as a needless extra risk to expose the crew to. But my thought is that the experience gained is likely to be of sufficient benefit to justify both that and the extra expense, at a point in the schedule where some minor changes are still possible before the real crewed mission.

[kdhilliard]

No, T-zero is after ignition, which occurs 2-3 seconds earlier. We have seen countdown aborts after ignition before. ...

I understand that. I was just assuming that with your proposal you intended them to stop before ignition.  So if not, then you are proposing they conduct a crewed, truncated static fire of only 2-3 seconds, then detank, disembark crew, clear pad, and conduct a follow-up full duration static fire.  I don't understand the benefit of having crew onboard during a static fire, no matter how long, but in any case we are drifting off topic.