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SpaceX: January 2006 Update

Published by Sigurd De Keyser on Tue Jan 10, 2006 8:56 am
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New Launch Time
The new launch time is February 8 at 4:30 p.m. California time with Feb. 9 as a backup day. We will actually be ready to launch earlier, but are planning to spend extra time reviewing and double-checking all vehicle systems.

Following the problem on Dec. 19, we flew a whole new first stage to Hawaii via C-5 just in time to catch the barge from there to Kwaj a few days before New Year’s Eve. The new stage should arrive at Kwaj in about a week, whereupon we will switch it out with the damaged unit, which will be sent back to California for repair. The repair is not particularly difficult or expensive, but can only be done properly in a factory setting.

What Was the Problem?
As previously reported, we traced the problem to failure of an electronic component in one of the first stage fuel tank pressurization valves. Although we have triple redundant pressure sensors and dual redundant pressurization valves, when this component shorted, it caused the valve controller board to reboot, effectively eliminating the redundancy.

This is the first time in 3.5 years of hard testing that we have ever seen this happen. Moreover, the component in question has a cycle life and power rating far in excess of the theoretical load that it should see. To address this specific problem, we are replacing the component with one that has a quasi-infinite lifespan and taking a few other steps that will isolate any issue with this component if it goes wrong in the future.

However, as I mentioned in an earlier update, we are not simply going to address this particular point problem and then merrily jump back into a countdown sequence. Throughout January, the SpaceX team will be doing another full review of vehicle systems, including propulsion, structures, avionics, software and ground support systems. We will be conducting additional engine tests, stage separation tests and avionics tests to once again attempt to flush out any issues. Even if we find nothing, the exercise is worthwhile.

Wind Delays Suck (Literally)
It is worth noting that we would have caught the problem without any damage to the vehicle if we had entered the final countdown sequence as planned. The sucked in tank damage only occurred because we partly drained the fuel tank due to the hold for high winds.

High winds are not a limitation of the rocket, which is designed to be essentially “all weather” and handle ground winds in excess of 50 mph (watch out for flying coconuts!). The ground winds limitation is actually due to the need to avoid a collision with the launch stand hold down arms, which grab the rocket at the base of the fuel tank, as the rocket lifts off.

To alleviate this problem, we have redesigned the launch stand so that the hold down arms retract out of the way on liftoff, activated by a breakwire. This gives us something very close to 100% winds availability from Kwaj. The retraction force is low, so even if there were an early activation of the actuator, it would not damage the rocket.

Another bothersome problem is the high rate of liquid oxygen (LOX) boiloff. This is not surprising when LOX is at -300F and there is a stiff wind impinging on the vehicle at 85F. To minimize boiloff, we will wrap the LOX tank in low cost cryo insulation attached with velcro straps that tear away on liftoff.

Lessons Learned on F1 Apply to F9
The challenges to date I think vindicate the strategy of building a small launch vehicle before a large one. If we had started out with an F9 class vehicle, the cost of every mistake would be multiplied by as much as an order of magnitude. As it is, we are able to overcome problems comparatively quickly and cheaply.

With the benefit of lessons learned on F1, it is taking far less time, effort and money to create F9. Despite the distraction of the F1 launch countdowns, I still anticipate a flight F9 first stage firing later this year and a maiden launch in late 2007.

Great Expectations Falcon 1 on the Omelek Launch Pad
Those familiar with the launch business will know that countdown scrubs are a way of life. It’s often said that the safest time to schedule your vacation is around launch day and that’s true more often than not. Even rockets that have launched hundreds of times from launch pads that are in heavy use have multiple scrubs. Not too long ago, there was a Titan launch that had eleven scrubs and Delta launch that had six.

Reasons range from hard to avoid technical glitches, like the Shuttle fuel sensor malfunction on its last launch attempt, to silly false alarms. A Titan countdown was once aborted when someone spotted a “bag of suspicious liquid” on the mobile service tower. It turned out that the latrine had simply been a bridge too far for one of the technicians.
Given that Falcon 1 is an all new rocket and is launching from an all new launch pad on a remote tropical island, countdown scrubs in the first few attempts were very likely. As it is, we have had one abort due to a launch pad issue and one due to the rocket. If this next attempt succeeds in getting to t-zero, SpaceX will be reasonably fortunate in the scheme of things.

—Elon—

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