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

[DigitalMan]

I don't recall whether this capsule has windows or perhaps they are covered.  Hopefully, one of the camera views will be looking past 'Starman' out a window.

[Mark K]

EDIT: I listened to the recorded version, and the "velocity vector" issue was the Russian concern about what would happen if the single (redundant) C&C box for Dragon-2 died during its approach to ISS.

Single redundant ...... sounds interesting. Anyway it is a legitimate question, but I think with good answers.
This multiple dissimilar approach has drawbacks as well which have been shown in some testing. I looked back to see if I could find the papers but couldn't find them. I think some go back a couple decades actually.

[Vasiliy]

Hi
I didn't understand what Bill Gerstenmaier said about warm propellant during Post FRR Press Conference.

On the thrusters, there's a portion of the thruster that can actually break free, and liberate, and come out of the thruster. I think we understand why that occurs. We can control that by operating the thrusters in a certain manner, keeping temperatures at a certain temperature, keeping the propellant conditions exactly the right way. In the future, we'd like to understand, to maybe make a change to that. To either keep the thermal system, keep the propellant warm in the vehicle without having to do attitude control to keep the propellant warm. So that'll be another change that's coming in the propulsion system.

Could someone explain?

[eeergo]

EDIT: I listened to the recorded version, and the "velocity vector" issue was the Russian concern about what would happen if the single (redundant) C&C box for Dragon-2 died during its approach to ISS.

Single redundant ...... sounds interesting. Anyway it is a legitimate question, but I think with good answers.
This multiple dissimilar approach has drawbacks as well which have been shown in some testing. I looked back to see if I could find the papers but couldn't find them. I think some go back a couple decades actually.

I should maybe have worded this better: it is a single box, but its systems are redundant inside. Russian concern was about: "what if the box seizes up and even while having redundant internal systems it cannot command Dragon and can't be swapped out by a spare? Answer will probably show it's not likely, or even possible, for the redundant systems to affect each other even if in the same box.

[eeergo]

Hi
I didn't understand what Bill Gerstenmaier said about warm propellant during Post FRR Press Conference.

On the thrusters, there's a portion of the thruster that can actually break free, and liberate, and come out of the thruster. I think we understand why that occurs. We can control that by operating the thrusters in a certain manner, keeping temperatures at a certain temperature, keeping the propellant conditions exactly the right way. In the future, we'd like to understand, to maybe make a change to that. To either keep the thermal system, keep the propellant warm in the vehicle without having to do attitude control to keep the propellant warm. So that'll be another change that's coming in the propulsion system.

Could someone explain?

My take is that the Dracos, as currently designed, have the potential to shed some components which can break free, likely due to temperature issues (propellant feed temps, exhaust expansion...?).

While redesigning the offending thruster piece would be ideal, they wouldn't want to delay the schedule for that, so an operational mitigation would be to avoid those cold temperatures, without obviously impacting other operations too much (hence the note about attitude control).

[kemen]

From the transcripted they seemed to be talking about making changes to fix the problem in the future. Does anyone with more inside info know, have more detail about that? Sounds like a long lead item, if they are going to force it to be change before certification.

[rsnellenberger]

Gerstenmaier mentioned a need/desire for a 24 hour docking time due to thermal constraints (presumably on Dragon). Since this is the first use of an IDA on-orbit, I’m curious what the contingency plans are for dealing with any issues that arise - how many attempts are possible, amount of “loiter time” available to diagnose/work issues, etc.

[eeergo]

Gerstenmaier mentioned a need/desire for a 24 hour docking time due to thermal constraints (presumably on Dragon). Since this is the first use of an IDA on-orbit, I’m curious what the contingency plans are for dealing with any issues that arise - how many attempts are possible, amount of “loiter time” available to diagnose/work issues, etc.

Sure, I meant redesign wasn't deemed as necessary for DM-1 to avoid messing with the schedule for that minor issue that can be mitigated procedurally - but they did mention it will be redesigned, possibly for DM-2.

However my info comes just from the briefing, so if insiders can share more, it will be more valuable than what I can gather from Gerst's comments.

[cuddihy]

I wonder if the thermal issue mentioned is related to the Draco low temp issue mentioned at the FRR debrief as a concern?

[ugordan]

I wonder if the thermal issue mentioned is related to the Draco low temp issue mentioned at the FRR debrief as a concern?

That was the impression I got.

[Yeknom-Ecaps]

Is there a list of tracking facilities that participate in the tracking of DM-1 at launch and in orbit? Does SpaceX use NASA, USAF and/or commercial tracking facilities to get data to Hawthorne mission control?

Thanks in advance for any information.

[joek]

I wonder if the thermal issue mentioned is related to the Draco low temp issue mentioned at the FRR debrief as a concern?

Likely.  I don't recall another thermal issue mentioned?  Also unclear if this is related to Draco or propellant thermals, or a combination.  Expect that they have been working on a fix as it may also be relevant to current cargo missions--do not see how issues with Super Draco would factor in given the implied context.

[joek]

Gerstenmaier mentioned a need/desire for a 24 hour docking time due to thermal constraints (presumably on Dragon). Since this is the first use of an IDA on-orbit, I’m curious what the contingency plans are for dealing with any issues that arise - how many attempts are possible, amount of “loiter time” available to diagnose/work issues, etc.

Original requirement was for docking up to 24hr after launch, with one retry within one orbit after that (see CCT-REQ-1130-146207-DRAFT-001-001 here).

No idea if that has changed since original requirements were issued.  If not, Gerst was likely reiterating the requirement.  Whether Dragon-2 can provide additional loiter time or docking retries is anyone's guess.

[marsbase]

Is there a list of tracking facilities that participate in the tracking of DM-1 at launch and in orbit? Does SpaceX use NASA, USAF and/or commercial tracking facilities to get data to Hawthorne mission control?

Thanks in advance for any information.

I understand that SpaceX is required to provide at least one tracking station outside of Florida.  They have an operational dish at Boca Chica.

[Yeknom-Ecaps]

Which "dragon" logo - wings or no wings - is associated with the Crew Dragon? I have seen both in articles.

Has the SpaceX DM-1 logo been released yet? Usually happens after the static fire but I haven't seen one.

Thanks.

[Alexphysics]

Has the SpaceX DM-1 logo been released yet? Usually happens after the static fire but I haven't seen one.

You mean the patch? The patch is released along with the press kit around 24h before launch.

[scr00chy]

Which "dragon" logo - wings or no wings - is associated with the Crew Dragon? I have seen both in articles.

I think the one with wings is an old logo that was superseded by the wingless logo. The old logo appears in some old cinematics so maybe that's why some people assume it's still used?

The DM-1 Crew Dragon only has the new logo painted on it: https://www.flickr.com/photos/spacex/31433487287/

[octavo]

In answer to a question about the drone ship landing, Hans said they were reserving performance and flying a lofted trajectory. He added that they may return to lz landings for future dragon 2 flights.

To me this implies that the booster will be landing with a lot of unused propellant if the flight goes well. Should we watch for a bit more crush core movement on landing, or does SpaceX have a way of using up that extra propellant on the way down by adjusting the landing burn on the fly?

[Lars-J]

In answer to a question about the drone ship landing, Hans said they were reserving performance and flying a lofted trajectory. He added that they may return to lz landings for future dragon 2 flights.

To me this implies that the booster will be landing with a lot of unused propellant if the flight goes well. Should we watch for a bit more crush core movement on landing, or does SpaceX have a way of using up that extra propellant on the way down by adjusting the landing burn on the fly?

The landing software is clearly pretty adaptable. And it takes more propellant to land more propellant. The software could also use different length burns depending on estimated remaining propellant.

[ZachS09]

In answer to a question about the drone ship landing, Hans said they were reserving performance and flying a lofted trajectory. He added that they may return to lz landings for future dragon 2 flights.

To me this implies that the booster will be landing with a lot of unused propellant if the flight goes well. Should we watch for a bit more crush core movement on landing, or does SpaceX have a way of using up that extra propellant on the way down by adjusting the landing burn on the fly?

I would say that they would tweak the landing burn a bit. Remember when the Falcon Heavy side boosters did a hoverslam-type landing burn? They used the 1-3-1 engine sequence and it took 17 seconds from the landing burn startup to touchdown.

I have a feeling they might do the same thing with the Crew Dragon first stage boosters from DM-2 onwards.