LIVE: SpaceX Falcon 9/Dragon CRS-2 (SpX-2) LAUNCH and FD-1 UPDATES

[Jason1701]

How are fuel tanks and thrusters connected?  is it one tank pair per thruster pod?  any cross-connects?

This image makes it look like there is one pair per pod. Can't tell cross-connects.

The image looks af each thruser is independent - it has its own fuel and sub systems.

Which begs the question what knocks out 3 of 4? 3 failing independently is not possible, and surely each one will have its own systems.

Normally when I can't figure this out I put it down to "compliler error".

Perhaps one of the valves connecting a propellant tank to a pressurization tank was reading incorrectly, and the computer was overzealous in inhibiting three of the four pods from being primed. As someone said, that sort of thing happened to F9 a number of times in its first few launches.

[corrodedNut]

The 4 pods don't seem to be equal, do they need specific pair of pods to do all maneuvers/burns?

Two pods have one extra forward pointing Draco (six total), for deorbit burns.

[Prober]

Woo-Hoo! This was SpaceX's true "baptism of fire" for me - any they performed like pros. Wish we could've gotten that stream though!

But, this isn't over yet - we know now that at least two pods are functioning, but there's still the other two. And this may yet affect the rendezvous plan for ISS.

maybe SpaceX can give L2 Members a special treat of the Solar deploy?  Hint Hint...

[psloss]

With mention of the ground sites, does that mean Dragon doesn't/won't have TDRS support (yet)?

I seem to remember that past mission(s) having that.

I believe you need to point your antennas very precisely for TDRSS, tough/impossible to do without certain thruster quads.

I imagine for comms with ground they use a different antenna that isn't as directional.

Other thing we were wondering about here was attitude to allow the arrays to track reasonably.

[Robotbeat]

The 4 pods don't seem to be equal, do they need specific pair of pods to do all maneuvers/burns?

Two pods have one extra forward pointing Draco (six total), for deorbit burns.

You can still do it with the other pods, but with some more cosine losses. You get less cross-coupling if you have opposing pairs.

[meekGee]

How are fuel tanks and thrusters connected?  is it one tank pair per thruster pod?  any cross-connects?

This image makes it look like there is one pair per pod. Can't tell cross-connects.

The image looks af each thruser is independent - it has its own fuel and sub systems.

Which begs the question what knocks out 3 of 4? 3 failing independently is not possible, and surely each one will have its own systems.

Normally when I can't figure this out I put it down to "compliler error".

softer errors...  A computer parameter that's been changes (and is system-wide)  some electrical fault that's affecting all sensors, etc.

Or, something absolutely horrific like bad fuel, but I think that's out of the question here since one (or two) pods are fine.

[mmeijeri]

I'm relieved the solar panels have deployed, but if they did it with only one thruster set running, doesn't that mean they haven't solved anything yet?

[Jason1701]

I'm relieved the solar panels have deployed, but if they did it with only one thruster set running, doesn't that mean they haven't solved anything yet?

No, they have raised one other pod to a substantially higher level of readiness. (Unconfirmed whether it is fully operational yet.)

[corrodedNut]

The 4 pods don't seem to be equal, do they need specific pair of pods to do all maneuvers/burns?

Two pods have one extra forward pointing Draco (six total), for deorbit burns.

You can still do it with the other pods, but with some more cosine losses. You get less cross-coupling if you have opposing pairs.

Yes. I'd wager that one functioning pod is about as useful as none, 2-pod failure can be sustained as long as the remaining two are opposite each other.

[Robotbeat]

I'm relieved the solar panels have deployed, but if they did it with only one thruster set running, doesn't that mean they haven't solved anything yet?

It means we don't know if they've solved it, yet. They may be taking their time.

[R7]

Yes. I'd wager that one functioning pod is about as useful as none, 2-pod failure can be sustained as long as the remaining two are opposite each other.

Two opposite pods needed for proper translation.

edit: yeah you can try all sort of wobbly gimmicks .. don't think NASA let's you anywhere near ISS with those. Will it let even without all four pods working?

[Robotbeat]

Yes. I'd wager that one functioning pod is about as useful as none, 2-pod failure can be sustained as long as the remaining two are opposite each other.

Two opposite pods needed for proper translation.

One functioning pod means they can still do attitude control (with translation cross-coupling). If they're very clever, they may be able to use it to do deorbit burn, too. And with two non-opposing pods, they should have enough degrees of control to do translation but with low efficiency. They'd want at least most of the thruster pods in full working condition before any kind of berthing.

[mlindner]

Yes. I'd wager that one functioning pod is about as useful as none, 2-pod failure can be sustained as long as the remaining two are opposite each other.

Two opposite pods needed for proper translation.

Technically you could de-orbit on one pod if you have the fuel. Thrust in one direction, wait for the spacecraft to rotate, then thrust in the opposite direction to null rotation and add more thrust (and reverse rotation). Kind of a back and forth weaving operation.

[Lee Jay]

26 minutes to planned coelliptic burn.

If they miss this burn, are they back to a multi-day rendezvous?

[Chris Bergin]

26 minutes to planned coelliptic burn.

Good milestone to look out for. Minutes away now.

[IRobot]

Yes. I'd wager that one functioning pod is about as useful as none, 2-pod failure can be sustained as long as the remaining two are opposite each other.

Two opposite pods needed for proper translation.

AFAIK, pod 1&3  are working, if sequence number makes normal sense, it might indicate that they are opposite.

[mmeijeri]

I don't think we know #3 is working now, we heard it was trending positive and that they would deploy the arrays soon, and then we got confirmation the arrays had deployed. This suggested #3 was working too, but apparently that was later denied since they said they were still working to get the remaining three operational.

[hrissan]

Yes. I'd wager that one functioning pod is about as useful as none, 2-pod failure can be sustained as long as the remaining two are opposite each other.

Two opposite pods needed for proper translation.

Technically you could de-orbit on one pod if you have the fuel. Thrust in one direction, wait for the spacecraft to rotate, then thrust in the opposite direction to null rotation and add more thrust (and reverse rotation). Kind of a back and forth weaving operation.

I thought about using just 1 of pods for translation (turning all 4 thrusters at once and then "pushing" the Dragon by varying thrust and balancing it like a pendulum on a finger). If this space ballet is possible, the Grasshopper maneuvers pales in comparison.

I doubt the Dragon software knows how to do it. After all, if 3 of 4 pods are dead, the last one will most likely be dead also soon.

[ugordan]

AFAIK, pod 1&3  are working, if sequence number makes normal sense, it might indicate that they are opposite.

Where does it say two are working?

[jcm]

26 minutes to planned coelliptic burn.

Good milestone to look out for. Minutes away now.

Given the status of the spacecraft I'll be rather astonished if they do the burn. I am assuming it will take most of today to recover the thrusters and check systems,
and then a replan.  SpaceX are aggressive but not reckless.