LIVE: Space Falcon 9 Flight 2 Static Fire - December 4, 2010

[mmeijeri]

I heard someone talking about new config files - this probably means they've been changing some parameters.

Ha, some old-fashioned CONFIG.SYS tweaking!

[ugordan]

If so, how'd it make it through acceptance firing?

Not only that, it made it through two integrated stage firings in Texas. Might be another one of the nuances between Cape and Texas ground support systems.

[ugordan]

Thanks! Two more question though: Does the oxygen keep venting even after the rocket is launched? Do they pump more oxygen into the tanks while the rocket is still standing to refill the lost oxygen, or are the losses really small?

After the LOX tank is mostly full, they enter the so-called topping mode where the boiloff losses are replenished. This lasts until shortly before launch when the relief valve is closed to pressurize the tank for flight. The boiloff is used to pressurize. After ignition and liftoff, the relief valve can occasionally open a bit to prevent overpressurization of the tank, but it keeps it at flight pressurization throughout flight.

[Lee Jay]

Hi, sorry for maybe a stupid question, but what are the fumes that come out of the rocket? And why are they there?

Cold Oxygen gas.  The liquid oxygen is cold (very cold) and the outside is warm.  So the liquid is boiling off into gas and the gas (like steam) has to go somewhere outside the tank to keep from over-pressurizing the tank.

What you see is actually condensed water, because of the cold oxygen that's venting out of the rocket.

Thanks! Two more question though: Does the oxygen keep venting even after the rocket is launched? Do they pump more oxygen into the tanks while the rocket is still standing to refill the lost oxygen, or are the losses really small?

Close to the launch, the tanks are pressurized and the oxygen stops venting.  During flight, the oxygen is being drained at a very high rate by the engines thus they need to fill the tank with gas at the same time to keep the tank pressurized.  Yes, they are replenishing the oxygen as it boils off.  The losses aren't that small because any insulation they have on the rocket has to be carried up so they want to minimize its mass.  Basically, it's enough to keep too much ice from forming on the side of the rocket from the cold oxygen and that's it.

[jabe]

If 9 pipes can drain a tank in 3 minutes....

I was going to ask where you read that but then logic kicked in

[Pedantic Twit]

Did anyone else catch the venting briefly stopping? Was it just the breeze?

[joshcryer]

SpaceX Next static fire attempt targeted for 10:50AM EST

Via facebook

edit, link: http://www.facebook.com/SpaceX/posts/179681385390731

[JohnWT]

Is there any connection between gas generator pressure and chamber pressure?  Could they have adjusted the former a bit too low in order to compensate for yesterday's problem?

[ugordan]

Is the strongback supposed to be venting as well?

[arnezami]

I heard someone talking about new config files - this probably means they've been changing some parameters.

I wonder whether they change of config of the engine itself or whether they change the config of de fault detection system. Also whether the changed config since yesterday caused this abort since the fault detection system might have been expecting a higher value for engine 6.

Anybody has any idea?

[Halidon]

Oddly enough, the stuttery feed was coming through just fine for me yesterday, but the new and improved feed just leaves me stuck at the "connecting" box. Frustrating.

[mr. mark]

I'm also worried about 6 being a lemon. What happens if this goes out in flight. Does it's position have anything to do with overall flight stability and control?

[ugordan]

Does it's position have anything to do with overall flight stability and control?

All the engines gimbal.

[Mark Max Q]

SpaceX Next static fire attempt targeted for 10:50AM EST

Via facebook

Keep up. That was posted a page or so ago

[corrodedNut]

"Readiness poll in 1 minute"

[e of pi]

We are counting! Polling...

EDIT: "Go, no holds required."

[Pedantic Twit]

Here we go!

[Chris Bergin]

Countdown restarted.

[brihath]

I'm also worried about 6 being a lemon. What happens if this goes out in flight. Does it's position have anything to do with overall flight stability and control?

I think that is thinking too far in the future.  A successful static firing should validate the engines.  I think they have been run on the test stand also.

I wonder if it has more to do with test limits rather than hardware.  I think that will all come out before they launch.

[Kabloona]

I'm also worried about 6 being a lemon. What happens if this goes out in flight. Does it's position have anything to do with overall flight stability and control?

It's not a lemon. The problem is that the start transients haven't been fully characterized, and the flight computer is being overly cautious by shutting down engine(s) whose parameters are outside a tightly prescribed window.