SpaceX Falcon 9/Dragon CRS-2 SpX-2 MISSION GENERAL DISCUSSION

[Ben the Space Brit]

They appear to have dealt with the issues with this flight & the previous one in a very professional & competent way.

How would you know?  We have no insight into what they are doing.

"They appear" - He was offering an opinion, Jim.  Ease off, will you?

[Garrett]

SpaceX said problem is with a valve

That doesn't necessarily mean the valve is mechanically defective - there could be a sensor on the valve giving an erroneous reading.

I can think of numerous probable valve issues :
- faulty power cable in
- faulty signal cable in
- faulty signal cable out
- valve stuck
- valve response not proportional to input (for a variable valve)
- valve indicating closed/open when flow meter/pressure meter indicates open/closed.
- pressure/flow control algorithm not locking on, giving impression of faulty valve (for a variable valve)
- leaking valve (e.g. in closed position)
- valve controller electronics faulty (if valve is mechanically controlled rather than pneumatically).
- pneumatic inlet valve faulty (for a pneumatically controlled check valve)

... and probably many more.

We have nowhere near enough info to speculate on what is the root cause of the issue.

[ugordan]

SpaceX said problem is with a valve

That doesn't necessarily mean the valve is mechanically defective

I'm sure it'll end up being a software fault, as suggested here 

[Jim]

They appear to have dealt with the issues with this flight & the previous one in a very professional & competent way.

How would you know?  We have no insight into what they are doing.

"They appear" - He was offering an opinion, Jim.  Ease off, will you?

An opinion based on no data.  It was something for the cheerleading thread

[Ben the Space Brit]

Elon is regularly tweeting updates.  If this is like any previous Dragon mission, he's at the front row in MCC-X.  Does he have a formal role in the flight, for example, effectively the Flight Director, or is he just there to watch the ride and is tweeting his impressions?

[R7]

SpaceX said problem is with a valve

Single valve fksup three pods? Bad valve.

[Ben the Space Brit]

They appear to have dealt with the issues with this flight & the previous one in a very professional & competent way.

How would you know?  We have no insight into what they are doing.

"They appear" - He was offering an opinion, Jim.  Ease off, will you?

An opinion based on no data.  It was something for the cheerleading thread

An opinion based on his observation and all publicly available facts.

[Chris Bergin]

Calm down chaps.

[Galactic Penguin SST]

So IF the thruster problem cannot be solved (knockwood), can the Dragon be brought down back for re-entry?

[Garrett]

So IF the thruster problem cannot be solved (knockwood), can the Dragon be brought down back for re-entry?

Due to atmospheric drag, it will come down eventually, with or without thrusters. Given the geometry of Dragon, I presume it'll probably come down intact, albeit in bad condition if they don't separate the trunk first.

[plank]

First software, then engine, now thrusters.  I hope this isn't going to be a routine.   

[cro-magnon gramps]

Elon is regularly tweeting updates.  If this is like any previous Dragon mission, he's at the front row in MCC-X.  Does he have a formal role in the flight, for example, effectively the Flight Director, or is he just there to watch the ride and is tweeting his impressions?

Typically, Elon is in the front row; the camera man in front of him there for Publicity Shots. no doubt...

[Galactic Penguin SST]

So IF the thruster problem cannot be solved (knockwood), can the Dragon be brought down back for re-entry?

Due to atmospheric drag, it will come down eventually, with or without thrusters. Given the geometry of Dragon, I presume it'll probably come down intact, albeit in bad condition if they don't separate the trunk first.

Yeah, but if you don't have efficient attitude control even ballistic re-entry may not be possible and the module may not survive intact. And what about post re-entry attitude control till parachute deployment?

BTW anyone remember what orbit did Phobos-Grunt got dumped into? I am thinking of the effect on drag on it and the Dragon and see how much time the Dragon has before it decays.

[R7]

Yeah, but if you don't have efficient attitude control even ballistic re-entry may not be possible and the module may not survive intact. And what about post re-entry attitude control till parachute deployment?

And what about where it re-enters?

[Robotbeat]

So IF the thruster problem cannot be solved (knockwood), can the Dragon be brought down back for re-entry?

Due to atmospheric drag, it will come down eventually, with or without thrusters. Given the geometry of Dragon, I presume it'll probably come down intact, albeit in bad condition if they don't separate the trunk first.

Yeah, but if you don't have efficient attitude control even ballistic re-entry may not be possible and the module may not survive intact. And what about post re-entry attitude control till parachute deployment?

BTW anyone remember what orbit did Phobos-Grunt got dumped into? I am thinking of the effect on drag on it and the Dragon and see how much time the Dragon has before it decays.

Once you start reentering ballistically and develop significant drag, I don't think you need ANY attitude control for a passively stable reentry vehicle.

[cro-magnon gramps]

So IF the thruster problem cannot be solved (knockwood), can the Dragon be brought down back for re-entry?

Due to atmospheric drag, it will come down eventually, with or without thrusters. Given the geometry of Dragon, I presume it'll probably come down intact, albeit in bad condition if they don't separate the trunk first.

Yeah, but if you don't have efficient attitude control even ballistic re-entry may not be possible and the module may not survive intact. And what about post re-entry attitude control till parachute deployment?

BTW anyone remember what orbit did Phobos-Grunt got dumped into? I am thinking of the effect on drag on it and the Dragon and see how much time the Dragon has before it decays.

Once you start reentering ballistically and develop significant drag, I don't think you need ANY attitude control for a passively stable reentry vehicle.

Isn't that assuming they can chuck the trunk safely... or will the trunk burn off and expose the shield... think they did that with one of the Apollo missions, leaving the thruster pack on, because telemetry said the shield had shifted...

[R7]

Once you start reentering ballistically and develop significant drag, I don't think you need ANY attitude control for a passively stable reentry vehicle.

Need to spin up a roll or it won't be purely ballistic. Questions about how the unloaded payload and unused RCS prop affects CG too.

[llanitedave]

So IF the thruster problem cannot be solved (knockwood), can the Dragon be brought down back for re-entry?

Due to atmospheric drag, it will come down eventually, with or without thrusters. Given the geometry of Dragon, I presume it'll probably come down intact, albeit in bad condition if they don't separate the trunk first.

Yeah, but if you don't have efficient attitude control even ballistic re-entry may not be possible and the module may not survive intact. And what about post re-entry attitude control till parachute deployment?

BTW anyone remember what orbit did Phobos-Grunt got dumped into? I am thinking of the effect on drag on it and the Dragon and see how much time the Dragon has before it decays.

Once you start reentering ballistically and develop significant drag, I don't think you need ANY attitude control for a passively stable reentry vehicle.

Isn't that assuming they can chuck the trunk safely... or will the trunk burn off and expose the shield... think they did that with one of the Apollo missions, leaving the thruster pack on, because telemetry said the shield had shifted...

That was John Glenn's Mercury flight, and the thruster pack was just a strapon canister of solid fuel.  Nothing like a heavy trunk.

[Robotbeat]

So IF the thruster problem cannot be solved (knockwood), can the Dragon be brought down back for re-entry?

Due to atmospheric drag, it will come down eventually, with or without thrusters. Given the geometry of Dragon, I presume it'll probably come down intact, albeit in bad condition if they don't separate the trunk first.

Yeah, but if you don't have efficient attitude control even ballistic re-entry may not be possible and the module may not survive intact. And what about post re-entry attitude control till parachute deployment?

BTW anyone remember what orbit did Phobos-Grunt got dumped into? I am thinking of the effect on drag on it and the Dragon and see how much time the Dragon has before it decays.

Once you start reentering ballistically and develop significant drag, I don't think you need ANY attitude control for a passively stable reentry vehicle.

Isn't that assuming they can chuck the trunk safely... or will the trunk burn off and expose the shield... think they did that with one of the Apollo missions, leaving the thruster pack on, because telemetry said the shield had shifted...

That was John Glenn's Mercury flight, and the thruster pack was just a strapon canister of solid fuel.  Nothing like a heavy trunk.

There's no reason whatsoever to think they wouldn't be able to jettison the trunk.

[cro-magnon gramps]

ok, thanks llanitedave and Robotbeat...