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

[IntoTheVoid]

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.

They won't do this for the reasons discussed months ago. NASA wants the loading sequence performed in the Crew manner with the new COPVs, 5 times before allowing crew on board for fueling operations. These 5 times are understood to be static fire (1), and launch of DM-1 (2), static file (3) and launch of In-Flight Abort (4), and static fire (5) of DM-2, before allowing crew to board for launch of DM-2.

This doesn't preclude the dry 'mission dress rehersals',as CorvusCorax described, which will certainly be done. But NASA won't be risking the Astros prior to the DM-2 launch.

[Roy_H]

I was under the impression that NASA required 5 practice crew loadings before flight mission. This would be the first opportunity. Also I understood that the crew would board, strap in, then get out and leave before fuel loading.

[jpo234]

I was under the impression that NASA required 5 practice crew loadings before flight mission. This would be the first opportunity. Also I understood that the crew would board, strap in, then get out and leave before fuel loading.

Are there even seats inside to strap in? It's supposed to carry cargo on this mission, after all.

[CorvusCorax]

I was under the impression that NASA required 5 practice crew loadings before flight mission. This would be the first opportunity. Also I understood that the crew would board, strap in, then get out and leave before fuel loading.

The crew can practice loading procedures with one of the practice dragon mockups they have safely. They can also do final "real ones" during one or more dry dress rehearsals before DM-2. with vehicle safe and no propellants on board.

In a real abort scenario, assume the engines ignite, sensors sense something wrong and the engines turn off again.

In the past, SpaceX has recycled within relatively short time after such an abort, if the cause was trivial, maybe not even requiring detanking, but that's not relevant for commercial crew as all launch windows are instantaneous. abort at t=0 automatically means scrub and try again a day later as there's no time for recycle.

But one can easily argue:

If the issue is really serious, (fire on the pad?) then the astronauts are safest in the dragon, if necessary utilising the superdracos for a pad abort

if the issue is not so serious, then the safest approach would be to detank, safe the rocket, then get the astronauts out.

there are scenarios thinkable where the crew needs to get out quick and use the escape baskets, but most of those would involve problems with dragon itself, or the crew (medical emergency of some sort) so they really need to get out quick.

if the rocket is the problem, it should be safer to leave the crew safely in dragon (and pad crew at minimum safe distance) until the vehicle is safe

[IntoTheVoid]

Dug up the reference, which was the July 2018 GAO Report (on pages 13 & 14), which was subsequently discussed in the 'General Falcon and Dragon discussion (Thread 14)'. Note the the bulletted item is "Propellant Loading Procedures", not Crew Loading Procedures.

Propellant Loading Procedures: Both the program and a NASA advisory group have raised SpaceX’s plan to fuel the launch vehicle after the astronauts are on board the spacecraft to be a potential safety risk. ...
To better understand the propellant loading procedures, the program and SpaceX agreed to demonstrate the loading process five times from the launch site in the final crew configuration prior to the crewed flight test. The five events include the uncrewed flight test and the in-flight abort test.

https://www.gao.gov/assets/700/693035.pdf

This is 4th party documentation of an agreement between the Commercial Crew program, SpaceX and ASAP to not have Astros on board during fueling until the above is complete. I don't imagine this changing.
And, any testing not involving fueling, is better performed during a time when they're not intending to be fueling.

[BunkerTheHusky]

Have we forgotten that this is an uncrewed test of the vehicle? There's plenty of time to practice boarding procedures yet before DM-2. Meanwhile, with complete respect to the brave people who will be riding and trusting their lives to this rocket, what would having meat cargo on board do for a static fire? It seems an unnecessary risk for systems that can be tested without human beings on board.

[Norm38]

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).

Space Camp 2.0?  Just keep the droids away from the launch computers.

[Norm38]

Propellant Loading Procedures: Both the program and a NASA advisory group have raised SpaceX’s plan to fuel the launch vehicle after the astronauts are on board the spacecraft to be a potential safety risk. ...
To better understand the propellant loading procedures, the program and SpaceX agreed to demonstrate the loading process five times from the launch site in the final crew configuration prior to the crewed flight test. The five events include the uncrewed flight test and the in-flight abort test.

https://www.gao.gov/assets/700/693035.pdf

I'm not following this logic.  The Dragon can pad abort on a hair trigger.  If the astros are strapped in before fueling and the tower crew evacuated, then at any time during fueling (or after), Dragon can abort.

If F9 is fueled before crew board, then there is a large amount of time where unprotected crew and personnel are standing right next to a fueled rocket.  Crew inside Dragon not yet strapped in will probably not survive an abort.

What this is saying is that fueling itself is orders of magnitude more dangerous.  But once the tanks are full and into topping off, the danger drops down to the point everyone can approach the vehicle.

But that is how Shuttle did it, so I guess that's what NASA is comfortable with.

[gongora]

This thread is drifting a bit.  DM-1 does not involve crew.  DM-1 is not going to have any wacky abort tests with people on board.  The reason NASA is requiring testing before putting people onboard during fueling is because they want to gather data and review procedures before putting people onboard during the fueling, I don't know what's so hard to understand about that.  Please get this conversation back to the actual DM-1 mission.

[MostlyHarmless]

If I recall, the original point of the immediate discussion was why SpaceX would have the spacecraft on the booster during static firing. 

Unlike satellite payloads, the Dragon 2 is (or at least could be) an active participant in the launch (it at least certainly monitors the progress of the launch, and must be as prepared as the booster, itself).  Thus, for the launch team to conduct a full "dress rehearsal" of the countdown and prep for launch, the Dragon 2 must be included in these static fire tests.

If you look at Omar Izquierdo's Tweet at:

https://twitter.com/izqomar/status/1088167736004562945

The image shows the spacecraft being serviced by the strongback.  That tells me that the prepping the Dragon 2 for launch needs to be part of the dress rehearsal.

At least that's my take on things.

[freddo411]

What is the purpose of the oddly shaped, cantilevered structure sticking out of the strongback opposite the dragon capsule?   Why all the odd angles?

[whitelancer64]

What is the purpose of the oddly shaped, cantilevered structure sticking out of the strongback opposite the dragon capsule?   Why all the odd angles?

I believe they are retraction aids for the Dragon's umbilicals. It's kind of hard to see in the picture, but there are wire cables going to yellow straps on the umbilicals.

Easier to see in attached picture.

[Lars-J]

What is the purpose of the oddly shaped, cantilevered structure sticking out of the strongback opposite the dragon capsule?   Why all the odd angles?

I believe they are retraction aids for the Dragon's umbilicals. It's kind of hard to see in the picture, but there are wire cables going to yellow straps on the umbilicals.

Easier to see in attached picture.

Ah, that makes sense. So when the strong back leans back, those arms will come forward and allow Dragon to be connected until liftoff.

[Johnnyhinbos]

It’s a magnificent looking stack. So happy to once again be launching humans to space (even if it’s just our own backyard) on American engineered spacecraft in the near future.

Question - beyond umbilical differences to the Dragon Crew capsule, what else is different in any way to a regular Block 5 static fire?

[pospa]

What is the purpose of the oddly shaped, cantilevered structure sticking out of the strongback opposite the dragon capsule?   Why all the odd angles?

I believe they are retraction aids for the Dragon's umbilicals. It's kind of hard to see in the picture, but there are wire cables going to yellow straps on the umbilicals.

Easier to see in attached picture.

I agree. Its even better visible on this latest picture.

[woods170]

What is the purpose of the oddly shaped, cantilevered structure sticking out of the strongback opposite the dragon capsule?   Why all the odd angles?

I believe they are retraction aids for the Dragon's umbilicals. It's kind of hard to see in the picture, but there are wire cables going to yellow straps on the umbilicals.

Easier to see in attached picture.

I agree. Its even better visible on this latest picture.

They are linear pullers.
There are two T-0 umbilicals on Crew Dragon. One on the Trunk and one on the Crew Module. Those linear pullers activate on T-0 and yank the umbilical connectors away from Crew Dragon, in conjunction with the TE rapidly falling away from the launching F9.
The linear pullers are angled the way they are because they are a compromise between two aspects of the design:

- To pull away the umbilical connectors under a certain angle.
- Ground clearance of this set-up when the TE is horizontal.

Once this thing finally launches you will all witness why this set-up is positioned the way it is.

[woods170]

What is the purpose of the oddly shaped, cantilevered structure sticking out of the strongback opposite the dragon capsule?   Why all the odd angles?

I believe they are retraction aids for the Dragon's umbilicals. It's kind of hard to see in the picture, but there are wire cables going to yellow straps on the umbilicals.

Easier to see in attached picture.

Ah, that makes sense. So when the strong back leans back, those arms will come forward and allow Dragon to be connected until liftoff.

No, the arms will not come forward. When the strong back leans back slightly, a few minutes before liftoff, additional lengths of wire cable will be unreeled from the retraction aids (also known as linear pullers). At T-0 the linear pullers will very rapidly reel in the wire cables to yank the umbilical connectors away from Crew Dragon.

They can be extremely rapid in their action as they will also perform the exact same function (pulling the umbilicals away from Crew Dragon) during a pad abort.

[Comga]

What is the purpose of the oddly shaped, cantilevered structure sticking out of the strongback opposite the dragon capsule?   Why all the odd angles?

I believe they are retraction aids for the Dragon's umbilicals. It's kind of hard to see in the picture, but there are wire cables going to yellow straps on the umbilicals.

Easier to see in attached picture.

Ah, that makes sense. So when the strong back leans back, those arms will come forward and allow Dragon to be connected until liftoff.

It does, thank you, but that makes the angle of these long objects (one on either side as seen in the second photo) all that harder to understand.
I can visualize these devices hauling in the connectors on the ends of the umbilicals as the strongback falls away after the instant of launch, but it looks like they will be pulling at odd angles, rather than straight down their length.
By what angle does the TE retract in the minutes before ignition, and by what distance will that separate it from the Dragon capsule?
Will those umbilicals be close to their length limit?
 

[Comga]

Separate question:
From memory, for all recent Falcon launches, the strongback is retracted at T-4:00.

For Crew Dragon, including DM-1, will the strongback be retracted before fueling, at T-35:00 so that the capsule has a clear escape path?
Particularly if the umbilical retractors are designed to work from the retracted position, it seems logical that it be retracted any time the LAS is primed to pull the capsule away from a dangerous situation.
"Dangerous situations" includes failures during fueling.

[dlapine]

So, would a static fire require that the strongback + crew accessway be pulled back from the stack before the fire?