SpaceX Falcon 9 / Dragon 2 : SpX-DM2 : May 27, 2020 : DISCUSSION

[Lars-J]

The meteorologists in Jacksonville FL love to insert SpaceX launches into their weather reports, and today one reported that almost the entire abort corridor was compromised, starting with a tropical storm off the coast of Charleston SC, and other disturbances going all the way to Ireland.

That told me early on the launch wasn't going to happen today, except as the SpaceX/NASA coverage went on, the abort zones were barely mentioned. Either the abort zone conditions have no bearing on go or no go, and only serve to prepare recovery crews without stopping them, or everyone knew the whole time they would have to scrub, but didn't want to toss the build up and the extensively prepared pre-launch coverage.

Well despite the Jacksonville meteorologists, the reason for the scrub was *local* weather, not down-range weather. The abort zones do matter, but perhaps the criteria are not what conventional wisdom suggests.

Also, it appears that Dragon can be programmed to hit certain abort areas, if weather is bad where an alternate spot is available. The SDs are used to adjust the impact point forward and backwards.

[Orbiter]

The meteorologists in Jacksonville FL love to insert SpaceX launches into their weather reports, and this morning one reported that almost the entire abort corridor was compromised, starting with a tropical storm off the coast of Charleston SC, and other disturbances going all the way to Ireland.

That told me early on the launch wasn't going to happen today, except as the SpaceX/NASA coverage went on, the abort zones were barely mentioned. Either the abort zone conditions have no bearing on go or no go, and only serve to prepare recovery crews without stopping them, or everyone knew the whole time they would have to scrub, but didn't want to toss the build up and the extensively prepared pre-launch coverage.

The local meteorologists were operating off conjecture, however well reasoned, as they do not have access to the abort zone constraints (I don't think anyone does). They wouldn't have begun to fuel the rocket if any of the abort zones were problematic, and like you mentioned, they didn't even mention it to the crew over the net as a concern.

[DigitalMan]

Also, they want to limit the amount of time before the Dragon catches up to the ISS. Some days will always make no sense to launch on, because they would enter the ISS orbital plane so far behind the ISS that they'd spend a day in orbit just catching up to where they'd be if they launched the next day. But also I suspect that they have a limit on how long Bob & Doug spend in the Dragon before rendezvous on this test flight in particular, so they're choosing days where that time limit can be met.

This was brought up in the press conference that was re-broadcast today, and actually just the opposite is true for this mission. It was said they could reach the station as quickly as Soyuz, but being a test mission, there are things the astronauts will need extra time to test in flight.

Plus they wanted to test sleeping.

[Joffan]

Also, they want to limit the amount of time before the Dragon catches up to the ISS. Some days will always make no sense to launch on, because they would enter the ISS orbital plane so far behind the ISS that they'd spend a day in orbit just catching up to where they'd be if they launched the next day. But also I suspect that they have a limit on how long Bob & Doug spend in the Dragon before rendezvous on this test flight in particular, so they're choosing days where that time limit can be met.

This was brought up in the press conference that was re-broadcast today, and actually just the opposite is true for this mission. It was said they could reach the station as quickly as Soyuz, but being a test mission, there are things the astronauts will need extra time to test in flight.

Technically, I guess it's true that Dragon can reach the station as fast as Soyuz, but that's a matter of orbital mechanics, not vehicle capability. It will always depend - for both vehicles - on where the ISS is in its orbit. The visiting vehicle can slow things down, but there are sharp limits on how much it can speed them up.

The quickest possible rendezvous probably does depend on vehicle ability to rapidly make the orbit raising burns in a controlled manner to a well-phased ISS, but the basic controlling factor is where the ISS is in its orbit.

[Jarnis]

Main limitation for fast timeline to docking is ISS phasing. Do they take the time to adjust ISS orbit to hit a specific date. For the first test launch, that seems optimistic.

Also Soyuz being the tank it is has far less tendency to scrub out a launch. Would suck to take the time and the propellant to phase ISS for a fast trip, then have Florida weather to mess it all up.

I'm sure they'll do faster ones eventually and there are no technical reasons why Crew Dragon or Starliner could not do them. Just that a very short trip requires pre-planning well in advance in the form of slightly adjusting ISS orbit to match a targeted launch date.

[Brunberg]

When they scrubbed, did they have time to safe the vehicle or was is still loaded when Dragon's hatch was opened?

[Jarnis]

All prop was offloaded and then launch abort system disabled before the crew access arm was brought back out. This was all nominal procedure with no rush.

Would have to be an odd emergency where they would resort to offloading the crew from a still-fueled rocket. Only obvious case I can think of is that launch is no-go but propellant offload is somehow not working but the vehicle is otherwise in a stable state. True emergencies would "offload" the whole capsule (go Superdracos) and if there is no emergency, they'll just sit tight with the LAS armed until rocket is safed.

[geza]

What are the function of the iPads, additional to the huge screens? They contain the manuals? Or, they are part of the system, and can be used to command the spacecraft, when the screens are difficult to reach under g-load?

Why are there mirrors on the astros' arm? I know that Mercury astronauts had the same, because they could not see some of the indicators without it. However, in a Dragon 2?

[kevinof]

Both astros handed over their name tags to their assigned Ninja. Must be part of the ritual/process they have in place.

I picked up on this..it looked like Behnken handed ninja #6 back a Spacex name tag he had aboard Dragon...maybe he offered to fly it to space for her ?

[woods170]

Finally, my goodness... the procedure to re-open the capsule manually. Almost looked like an escape room from the outside. Many tools, different people and I am not sure whether they had practiced this before. Can imagine a loaded Falcon triggers different/extra safety mechanisms for the locks.

Multiple incorrect assumptions in your post.

1. The team has practiced this procedure several times. It is supposed to go slow. No need to hurry when your dealing with an explosive charge.
2. Several different tools required because several things need to be done to open that hatch from the outside, including removing the TPS insert, removing thermal barrier, removing pressure equalization plug, disarming EEC, and finally unlocking the hatch.
3. Loading the Falcon with propellants does NOT trigger extra safety mechanisms for the Crew Dragon hatch.

You may have noticed that, when the countdown was proceeding and the close out crew had left the pad, that Doug and Bob were informed that : from this point forward emergency egress would be unassisted".

That unassisted egress includes opening the hatch from the inside. Bob en Doug can open the hatch from the inside in a matter of 5 seconds: open the guard to a certain physical button. Press that button. Then press the confirm button within a few seconds. That triggers a small explosive charge which releases the crew hatch.

The crew also has controls to rotate their seats on their own. Getting out of their five-point harnesses is a matter of pressing a single physical button.

The astronauts can get themselves out of Crew Dragon in less than 20 seconds if they really have to.

[MATTBLAK]

During a scrub; do they de-tank the kerosene after the LOX? Is the Kerosene ever left in the vehicle for next time?

[kevinof]

From what I could hear on the scrub yesterday, it sounded like they empty both. It is chilled so keeping it in the tanks on the F9 would not work - off load it, chill and re-cycle.

During a scrub; do they de-tank the kerosene after the LOX? Is the Kerosene ever left in the vehicle for next time?

[trebloc]

Backup dates are this Sat and Sun but weather is not looking great at the moment. Has anyone any idea what dates and time are available after Sunday?

[woods170]

From what I could hear on the scrub yesterday, it sounded like they empty both. It is chilled so keeping it in the tanks on the F9 would not work - off load it, chill and re-cycle.

During a scrub; do they de-tank the kerosene after the LOX? Is the Kerosene ever left in the vehicle for next time?

Correct. LOX and RP-1 are off-loaded simultaneously.

[dgates]

Will the Falcon9 stay vertical, or will it roll back to the HIF?

[darkenfast]

Will the Falcon9 stay vertical, or will it roll back to the HIF?

I can't remember who said it during the broadcast, but the statement was that the Falcon would remain vertical unless they needed to work on something.

[darkenfast]

Finally, my goodness... the procedure to re-open the capsule manually. Almost looked like an escape room from the outside. Many tools, different people and I am not sure whether they had practiced this before. Can imagine a loaded Falcon triggers different/extra safety mechanisms for the locks.

Multiple incorrect assumptions in your post.

1. The team has practiced this procedure several times. It is supposed to go slow. No need to hurry when your dealing with an explosive charge.
2. Several different tools required because several things need to be done to open that hatch from the outside, including removing the TPS insert, removing thermal barrier, removing pressure equalization plug, disarming EEC, and finally unlocking the hatch.
3. Loading the Falcon with propellants does NOT trigger extra safety mechanisms for the Crew Dragon hatch.

You may have noticed that, when the countdown was proceeding and the close out crew had left the pad, that Doug and Bob were informed that : from this point forward emergency egress would be unassisted".

That unassisted egress includes opening the hatch from the inside. Bob en Doug can open the hatch from the inside in a matter of 5 seconds: open the guard to a certain physical button. Press that button. Then press the confirm button within a few seconds. That triggers a small explosive charge which releases the crew hatch.

The crew also has controls to rotate their seats on their own. Getting out of their five-point harnesses is a matter of pressing a single physical button.

The astronauts can get themselves out of Crew Dragon in less than 20 seconds if they really have to.

Thank you for that explanation.  Would I be correct in assuming that there is also a method for rescue personnel to get into the capsule in a hurry (either on pad or after a landing, in an emergency)?
 

[rdale]

The meteorologists in Jacksonville FL love to insert SpaceX launches into their weather reports, and this morning one reported that almost the entire abort corridor was compromised, starting with a tropical storm off the coast of Charleston SC, and other disturbances going all the way to Ireland.

Speaking as a former TV meteorologist, and current NSF Assistant to the Chief Meteorologist, I'll chime in to note that sometimes TV meteorologists are asked to speak on areas they aren't experts in. They have two options - deflect and find out later, or make stuff up on the fly.

Sounds like they chose option two

The tropical storm was onshore by launch time with wave heights quite reasonable near the recovery zone. There were some disturbances in the Atlantic, but nothing out of the ordinary. And there was a call that to the crew that the abort settings would be modified probably due to some areas of unsettled weather.

That told me early on the launch wasn't going to happen today

They were wrong to have said that. Monitor the USAF 45th Weather Squadron forecasts for the official ones and the NSF forecasts for the play-by--play next time.

everyone knew the whole time they would have to scrub, but didn't want to toss the build up and the extensively prepared pre-launch coverage.

I hope they didn't really say that...

As you can tell by my summary - it was local weather. There was too much electricity in the air as result of storms south of the launch site. That happens sometimes - it wasn't even listed as a factor in the official forecasts because it's not really possible to forecast electric fields.

I did talk to the National Weather Service Spaceflight Meteorology Group yesterday asking about more weather data going online. For now you have to catch it when it's on the low-res snapshot stream. He said that most everything was taken offline a few years ago and there are some plans to get it back on the world wide web but no estimate.

[Herb Schaltegger]

... (SNIP) ...

Just wanted to say I’m glad to see your extensive launch weather support posts yesterday! I used to really appreciate them during Shuttle days!

[ZachS09]

What I don’t understand is why they’re targeting Saturday and Sunday when both have 60% POVs.

I feel they should wait longer and choose a date that has at most 25%.