Author Topic: LIVE: SpaceX Falcon 9/Dragon CRS-2 (SpX-2) LAUNCH and FD-1 UPDATES (Read 278941 times)

Kabloona · « **Reply #460 on:** 03/01/2013 07:23 pm »

Quote from: AJA on 03/01/2013 07:22 pm

Quote from: Jim on 03/01/2013 07:16 pm
Quote from: kevin-rf on 03/01/2013 07:13 pm
Quote from: Chris Bergin on 03/01/2013 07:11 pm
All four oxidizer tanks holding their pressure now.

Does this mean that they used up pressurant (I assume helium) to try to bring the tanks up to pressure and now have reduced pressurant available for the rest of the mission?

It doesn't go overboard. The helium is in high pressure bottles and isolated from the prop tanks. As prop is used, the helium has to be added to the prop tank to maintain pressure.

Wait, how do you cycle without dumping some Helium? As in, once you pressurise higher, to cycle back down to low pressure on the Oxidiser, don't you have to dump some gas?

They cycled the Helium valve open/closed/open closed. They did not dump He. It's a closed system. The He goes into the OX tank(s).

Star One · « **Reply #461 on:** 03/01/2013 07:25 pm »

No leakage or debris as far as they are aware.

wronkiew · « **Reply #462 on:** 03/01/2013 07:25 pm »

Musk: Noticed thruster problem after separation. Oxidizer pressure in 3 of 4 tanks was low.

Chris Bergin · « **Reply #463 on:** 03/01/2013 07:26 pm »

Potential first opportunity is Sunday.

iamlucky13 · « **Reply #464 on:** 03/01/2013 07:26 pm »

Quote from: JimO on 03/01/2013 06:45 pm

It's not too early to ask, but maybe in bad taste: what is the expected orbital lifetime of an inert 'Dragon' in its current orbit? If thrusters are not required, are we looking at an unguided random reentry?

Roughly 320 km x 200 km orbit, from previous posts.

Digging through old info, Fobos-Grunt took about 2 months from ~350 km x 210 km.

In addition to phasing, the lower altitude also raises fuel-budget concerns due to the greater drag.

Quote from: Jason1701 on 03/01/2013 04:19 pm

Quote from: alexterrell on 03/01/2013 04:17 pm

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.

A possible intentional response to a some types of faults would be to enable the minimum needed to provide attitude control (1 pod).

We won't know for certain unless SpaceX tells us.

R7 · « **Reply #465 on:** 03/01/2013 07:26 pm »

How does one cycle a check valve without releasing pressure somewhere?

Star One · « **Reply #466 on:** 03/01/2013 07:27 pm »

Elon was asked what were the implications if crewed flight.

mmeijeri · « **Reply #467 on:** 03/01/2013 07:28 pm »

Quote from: R7 on 03/01/2013 07:26 pm

How does one cycle a check valve without releasing pressure somewhere?

And how do you pressure hammer a valve without cycling another valve?

Kabloona · « **Reply #468 on:** 03/01/2013 07:28 pm »

Quote from: R7 on 03/01/2013 07:26 pm

How does one cycle a check valve without releasing pressure somewhere?

They cycled the He isolation valve. The check valve is downstream from the iso valve. Cycling the iso valve may have "hammered" the check valve, or other obstruction, downstream to free it.

Possible also that the iso valve itself was stuck closed/partially closed, and that cycling freed it up.

simonbp · « **Reply #469 on:** 03/01/2013 07:29 pm »

Crew dragon has no solar!

Star One · « **Reply #470 on:** 03/01/2013 07:29 pm »

Elon says no solar arrays for crewed flight just battery power. Could also de-orbit with just one pod.

mlindner · « **Reply #471 on:** 03/01/2013 07:29 pm »

Elon:

We're not actually planning on having solar panels on crewed dragon. We're just going to have a very large battery.

!!!!?!

Lar · « **Reply #472 on:** 03/01/2013 07:29 pm »

E super worst case... we can deorbit with just one quad working... not easy but it's doable

wronkiew · « **Reply #473 on:** 03/01/2013 07:29 pm »

Musk: Extended solar arrays to slow rotation and to keep the solar arrays from getting too cold.

reubenb · « **Reply #474 on:** 03/01/2013 07:30 pm »

Solar arrays would be on longer duration missions, but not on ISS missions.

meekGee · « **Reply #475 on:** 03/01/2013 07:30 pm »

yeah, interesting. no solar on crewed dragon. straight from the horse's mouth.

Star One · « **Reply #476 on:** 03/01/2013 07:31 pm »

Quote from: meekGee on 03/01/2013 07:30 pm

yeah, interesting. no solar on crewed dragon. straight from the horse's mouth.

Is this to save mass that they would go this route, didn't catch all his answer on this.

meekGee · « **Reply #477 on:** 03/01/2013 07:31 pm »

Quote from: Lar on 03/01/2013 07:29 pm

E super worst case... we can deorbit with just one quad working... not easy but it's doable

Now had he said "it'd be like a one-armed rower" than we'd know what he'd been reading over the last hour...

wronkiew · « **Reply #478 on:** 03/01/2013 07:32 pm »

Musk: Less than an hour before enabling #2 and 3.

AJA · « **Reply #479 on:** 03/01/2013 07:32 pm »

1. Does anyone have an image of these valves?

2. Are they going to fire the thrusters associated with that tank? From what Elon said, they're planning on doing so. If the impediment was some solid contaminant, and now it's in the ox tank, might it get lodged in the oxidiser feed line to the Draco combustion chamber?