SpaceX Falcon 1 webcast

[Dr Mordrid]

Hearing it was a separation failure then the 2nd stage fired - boom.

Another F1 test flight is scheduled for later this quarter.

[Dr Mordrid]

Elon's sent a public e-mail:

It was obviously a big disappointment not to reach orbit on this flight. On the plus side, the flight of our first stage, with the new Merlin 1C engine that will be used in Falcon 9, was picture perfect. Unfortunately, a problem occurred with stage separation, causing the stages to be held together. This is under investigation and I will send out a note as soon as we understand exactly what happened.

The most important message I’d like to send right now is that SpaceX will not skip a beat in execution going forward. We have flight four of Falcon 1 almost ready for flight and flight five right behind that. I have also given the go ahead to begin fabrication of flight six. Falcon 9 development will also continue unabated, taking into account the lessons learned with Falcon 1. We have made great progress this past week with the successful nine engine firing.

As a precautionary measure to guard against the possibility of flight 3 not reaching orbit, SpaceX recently accepted a significant investment. Combined with our existing cash reserves, that ensures we will have more than sufficient funding on hand to continue launching Falcon 1 and develop Falcon 9 and Dragon. There should be absolutely zero question that SpaceX will prevail in reaching orbit and demonstrating reliable space transport. For my part, I will never give up and I mean never.

Thanks for your hard work and now on to flight four.

[Nowhere]

Doc, I wonder until which failure of Falcon you'll remain optimistic/when you'll put it in the same bucket as Shuttle

BTW, ashes of Scotty were aboard: http://science.slashdot.org/article..../08/04/1259259 (guaranteeing /. discussion with as many "scottisms" as possible ;> )

[Dr Mordrid]

For every nation or company that has developed rockets it's gone the same way; it's like watching how they make sausage - never a pretty operation. Remember the US program in the 50's when many rockets blew up on the pad or shortly after launch? Remember the Russian N-1 that blew on the pad killing a sh*tload of their rocket engineers?

This problem with this launch (F1-3) was that the explosive bolts (manufactured by a 3rd party that makes them for other rocketeers) that were supposed to do the separation misfired. No separation is a no-no.

I'd be willing to bet that before the next F1 flight (in a few weeks) that system is changed to the other commonly used system: linear shaped charges around the perimeter of the carbon composite interstage. 2nd bet is that this is immediately implemented on the Falcon 9.

One thing's for certain: they will get it right, and soon. Hell, these aren't beginners - muych of their team came over from Lockheed, Boeing and NASA.

Even though there was this failure the rest of the rocket worked fine; the Merlin 1C was perfect, the avionics worked and they once again demonstrated the ability to have a fault (the kerosene fuel temp too low hold), de-tank, re-tank with warmer fuel then launch within an hour. That alone is pretty impressive as such a fault would have had NASA scrubbing for another attempt a week or month later.

A bit of history: the F1-2 failure was due to fuel sloshing in the 2nd stage tank - it needed more baffles. Outside analysts had told SpaceX those weren't necessary, so blame can be shared on that one. The F1-1 failed shortly after launch because a stainless steel engine bolt had corroded from the salt water environment; basically the manufacturer sent them a faulty set of parts.

[Nowhere]

But... since you're saying those people aren't new to the game...and Falcon desing doesn't seem to be unorthodox (like for example the one of, underfunded, N1, which BTW didn't kill Russian engineers; you're thinking about ICBM disaster a decade before)...than why they're performing as if they'd try to figure things out?

BTW, idea/I wonder - how possible it would be that bolts were negativelly influenced by fuel problem/temperature prior to launch?...

[Dr Mordrid]

Turns out it wasn't the explosive bolts as had previously been suspected - those worked perfectly - it was a thrust transient in the 1st stage engine after the 1st stage shutdown.

Basically it comes down to a difference between the previously used Merlin 1B engine, which used an ablatively cooled nozzle (which shuts down quickly), and the new regeneratively cooled Merlin 1C used in this flight.

In a regeneratively cooled engine the fuel is run through tubes surrounding the thrust chamber and nozzle before it's burned. This preheats the fuel while also cooling the chamber and nozzle. Ablative engines are made of a heavier more heat resistant material, usually niobium, which makes them simpler but the lack of preheating lowers their efficiency.

In this case what happened was residual fuel under pressure in the regeneration system + a bit of O2 left in the chamber caused a very small amount of thrust even after the 1st stage shutdown.

Thrust transients are a known factor with regenerative engines, but the trick is in timing an early engine shutdown, measured in small fractions of a second, to compensate. SpaceX had set up an earlier 1st stage shutdown to compensate for the transient, but it wasn't enough, which caused the 1st and 2nd stage to collide shortly after separation.

In their defense is the fact that this thrust was so tiny that it didn't register on their test stand in Texas - a matter of <10 psi.

How often does this happen with new regenerative engine designs? Pretty often. Boeing, Lockheed and Orbital - probably the Russians and ESA too - have experienced larger than expected transients with new regenerative engine designs. You never really know until you fly the SOB.

Based on the telemetry they now have the right number and will be launching the next Falcon 1 sometime in September or early October.

SpaceX did list the following;

Good Things About This Flight

• Merlin 1C and overall first stage performance was excellent
• The stage separation system worked properly, in that all bolts fired and the pneumatic pushers delivered the correct impulse
• Second stage ignited and achieved nominal chamber pressure
• Fairing separated correctly
• We discovered this transient problem on Falcon 1 rather than Falcon 9
• Rocket stages were integrated, rolled out and launched in seven days
• Neither the near miss potential failures of flight two nor any new ones were present