Interview: a tour of SpaceX (part 3)by Sam Dinkin
|
| Omelek “is a little island that barely peaks out above the water, barely a third of a meter at low tide.” |
This is where they pull the ICBMs from the United States and do “glory trips,” as they call them, to make sure they are functional, operational. They ship them over to Vandenberg, throw them in a silo, instrument them, put a flight termination system on them, fire them off, and impact them right into the lagoon. All kinds of methods are used to score them.
TSR: That’s why they set up shop there so they have all the tracking already.
Bjelde: Yes.
Bill Boland, Space Frontier Foundation winner of VIP tour: Why did you need two facilities? Why did you create the second one?
Bjelde: There is no actual launch site on Kwajalein. It’s an Army base. People live there. That’s where the control room is. It’s not safe to launch from there. The launch sites in the past have been strewn about all these little islands in this ring.
Gosier: This isn’t one island—
Bjelde: —it’s a coral reef.
TSR: It’s like we are looking at the outline of a Hawaiian island, except it’s only the edge.
Bjelde: The islands are these little yellow pieces that come above water. You can see Kwajalein here, it’s a big J shape. Omelek we sublease from the US Army.
TSR: How big is Kwajalein island?
Bjelde: It’s 5 kilometers in length, maybe not even 1 km width. Our island is .03 km2 at low tide. It is tiny. At high tide, we are maybe left with .02 km2.
It’s a small little area in the middle of nowhere. Everyone knows what everyone is doing when we were out there. I got a chance to spend three months when we were out there last year. These guys are mostly Boeing guys working out at ’Mek, supporting the Missile Defense Agency. These guys are very friendly.
TSR: Is there a hotel, or just an army base?
Bjelde: It’s dormitory style, but it is a hotel. It called the Lodge. Kwajalein Lodge.
TSR: Did you get to do any diving there?
Bjelde: There are shipwrecks all over. What’s amazing about it is that not many people can dive there. You have to have authorization to get in there—it’s controlled waters.
Shock and awe
TSR: This is the bottom part of the top fairing before you put the cap on it?
Molina: Right, that would be the avionics so you can get an idea. Just to note, we do a lot of our own testing, too. Not only did we bring the manufacturing in-house, but we do some of the testing as well. We have shock tables over there.
Gosier: Shock? Buffet?
Molina: Yes, shock to mimic the worst-case scenario.
TSR: I thought you were going to mimic a lightning strike.
Molina: No, but we had an incident with lightning in Texas. There are some raging storms down there, too. Lightning is not our friend down in Texas.
This is the brain of the rocket. This is the avionics bay where all the components will sit. The two most expensive ones being the flight termination points. We do thrust termination instead of having explosives on the vehicle.
Boland: That was a big issue, wasn’t it?
Molina: Absolutely, because it is not a usual way of doing this. SpaceX tends to do what hasn’t been done.
TSR: Seeing as we want to carry people in it—
| “The whole thing is revolutionary. It’s not just one single thing.” |
Molina: —not having explosives is a good thing. Brian has to do a lot of work showing the impact. Getting that approved was a huge part of what he was brought in to do and he will then now be joining my team, and doing business development.
TSR: So this is not explosives, fairly standard rocket circuitry.
Molina: Absolutely, very simple. We had a guy who was in the business and saw this and said, “These are Radio Shack components!” We never pretend to be something we’re not. Simple is reliable. A lot of folks keep asking us, “What is technically revolutionary?”
TSR: Making money?
Molina: It’s more than that. The business plan and how we are doing this. The team approach that we are bringing together, the ideology of it. The whole thing is revolutionary. It’s not just one single thing. The one true innovation that SpaceX can point to is here the vehicle is run on ethernet. It’s very simple again, simple relating to reliability and to cost being the two things. Fewer things to go wrong and fewer things to cost a lot of money.
Flight termination
Bjelde: This is avionics: guidance qualification, control software, hardware; all the electronics that steer the vehicle, get it where it’s supposed to go and destroy it should something go bad.
Boland: Were you involved in the process of approval for the flight termination?
Bjelde: You are talking to the right person. I designed and qualified the flight termination system.
Boland: Do you feel that the certification process was fair? Certainly it must have been onerous, but was it fair?
Bjelde: It was onerous, but I think it was very fair. The guidelines they set are for a reason. If you are flying out of Santa Barbara, there have been misses in the past. It is very easy to make mistake in the guidance algorithm code if a left turn turns into a right turn. It would be bad publicity, right, if we impact into Los Angeles?
Molina: Don’t do that.
Bjelde: Very onerous. The technical requirements are very stringent. You typically are required to get three nines reliability. You fly with redundant components. The two ranges we have worked with thus far know the requirements are very onerous, but they are very open and willing to tailor it. So when there are regulations that say your flight termination antennae should be fungus resistant, normally you have to go out to take it to test houses. Maybe there is some component that at some time had parts that were susceptible to grow fungus that shorted. So the requirements there maybe don’t apply to us. They’ll look at that. Maybe they don’t apply to our system. They tailor the requirements to us as need be.
Hardware in the loop (HitL) testing
Bjelde: What is really enabling us to drive down the cost of launch vehicles we are going to offer is where, traditionally, you’ll have a larger company that manages contractors. There are a lot of aerospace companies around that built some component and qualified it back in the ’60s and ’70s. It’s space qualified and certified. It’s a million-dollar qualification some time ago. No one wants to rebuild the wheel. We were willing to do so. We brought some of the test capabilities in-house. We now control our assets, our schedule, everything.
Gosier: Is your guidance software homegrown? Are we talking several million lines of code?
Bjelde: Yes, but the length is, even if you include test code, about 40,000 lines. I think it’s really, really trim. We fly solid state memory: a little compact flash card and off we go. You know Elon, that’s the one thing he told us. His friends in Silicon Valley would never let him live it down if we messed up the software.
Here is our HitL system. We have two independent people, one that writes the code and one that writes the simulation. They’ll go head to head. We’ll plug in the code into the flight computer and run it. That’s a good segue into our thrust vector control [TVC].
TSR: When I took physics at Caltech, I took the tester code and copied it into place. How do you stop people from doing that?
Bjelde: You’re good. We take away the control button and the V button so people can’t paste. This is a HitL rack. These things you see down here simulate every valve, every pyro that’s on the vehicle.
| “No one wants to rebuild the wheel. We were willing to do so. We brought some of the test capabilities in-house. We now control our assets, our schedule, everything.” |
We’ll plug all those in to one of our flight computers or engine computers. You’ll have a flight computer that is running the vehicle. It’s making commands that to the first stage engine, an engine computer. It’s making commands that go out to valve controllers and TVC controller boards. Then, we run the code and validate it and perturb it. We’ll give it a good wind, a ground wind case or something. We’ll watch TVC correct. We watch the guidance. We’ll watch all the quaternions on the screen.
You have a universal gimbal mount there. We’re kicking off actuators. They use RP-1 fuel as their hydraulic fluid. We plumb it. The first stage is turbopump-fed. We tap off the side of the high-pressure side of that turbopump. It feeds back, so we conserve all that. If we ever ran out of hydraulic fluid, we ran out of propellant as well.
Rick Tumlinson, Spokesman, Space Frontier Foundation: There’s a story, a myth story out there. There was a meeting way back when you were going to launch from the airport. Someone from range safety said to Elon, “How can I be sure that your equations are working all the time?” He said something like, “At PayPal we did X million transactions per day and our failure rate is like nothing, can you say the same thing?” The guy shut up apparently.
Bjelde: I wasn’t sitting in that meeting. I’ve heard something like that. I won’t argue that. That sounds very Elon-esque. I think he said a few times, “You can’t fiddle around with other people’s money.”
Right here, the complement to the stand on the right is the second stage thrust vector control stand. Here we employ electromechanical actuators (EMA). We don’t have the luxury of having of turbopump-fed upper stage, it’s actually pressure-fed. This is an example of where we went to industry and said we need an actuator that runs on this voltage, this battery, and does this. They made proposals to make them for us, but they were just ridiculous amounts. This is an example of where we threw a little bit of our own engineering in and the investment truly paid off.
TSR: They’re used to people who are willing to pay cost plus.
Bjelde: That’s right. Now we have a wonderful electromechanical actuator that runs on a 28-volt bus.
Bjelde: We qualified it in house. Vib’ed it. Shocked it. Thermal cycled it. Vacuum tested.
TSR: When you stick it in the microwave oven, is that like a radiation simulation?
Bjelde: We don’t do that; we should actually. Not bad. It’s RF as well. We could do that.