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A chat with Bob Twiggs, father of the CubeSat

Posted: March 6, 2014

In part two of our interview with Bob Twiggs, a co-founder of the CubeSat, he gives advice to organizations interested in building a CubeSat, answers concerns about space debris, and gives his thoughts on the International Space Station as a launching platform for small satellites.

Three CubeSats sponsored by the European Space Agency are pictured next to their P-POD deployer mechanism. Photo credit: ESA/A. Reyes
Question: What types of materials are used in CubeSats?

Twiggs: We say that you have to build it with materials that meet space standards. You don't want to build it out of something that outgasses a lot after you get it into space, and that kind of dictates you build something out of metal. So aluminum is the easiest thing to do it with, and, of course, it has to fit that form factor to fit in what they call the P-POD launcher. We just said, "Rather than you build what you want and we'll try to fly it for you, we've got this launcher, it does some good things and you should use it."

First, it holds three CubeSats. The expendable launch vehicle guys like it because we don't have some student thing that can come off and run into the primary satellite, so that solved the problem with them. They were very cautious about putting something out in the open that parts could come off of, so we told the we've got this thing inside this metal container, and if a radio comes on, you're not going to hear it because it's inside of a Faraday cage. If parts come off it, the primary payload is going to get launched before we do, so when we launch, if it comes out in a whole bunch of pieces, it still won't affect you. It was really designed to help protect the primary satellite on the launch vehicle, and that loosens up the restrictions.

But, in fact, even with that, we went quite a few years where the only launches we could get were from the Russians. It wasn't until the Minotaur (rocket) came along that we were able to get any of our satellites launched in the United States.

Question: Was the CubeSat form factor open-source from the beginning?

Twiggs: It was open-source. That was the intent from the very beginning. It turned out, I think, one of the first that used it was the National Science Foundation. I talked to Therese Moretto Jorgensen (director of NSF's CubeSat program). We got a call to go to a conference at NSF where they wanted to look at using CubeSats for some of their scientific missions, and the result of that was the RAX satellites coming from the University of Michigan.

I talked to Therese about that and asked why it took them something like eight years from the time it was proposed until they decided to use it. She said they were watching to see what happened. If it turned out to be something good, they would use it. If it didn't, they would have not taken any risk with it.

They did it, and all of a sudden people started looking and saying, "Gee-whiz, I can do a really low-cost mission." It just snowballed from there.

NASA's PharmaSat spacecraft, based on a three-unit CubeSat design, monitored the growth of yeast cells in microgravity after its launch in 2009. Photo credit: NASA/Christopher Beasley
Question: Did you ever think CubeSats would take off the way they have?

Twiggs: Absolutely not. I don't think Jordi Puig-Suari (Cal Poly) did either. If we were still doing this for university education, that would have been fine with me. But it's very interesting to see other people adopt the concept and actually make use of it. So that's pretty good. I thought maybe we were building at Edsel but it turns out we were building a Mustang.

Question: So CubeSats are a more modern example of American innovation?

Twiggs: Yes, exactly, which makes it ironic that the early launch providers were Russian. We did go to some of the American launch providers, Lockheed Martin comes to mind, and they said, "If you give us a half-million dollars, we'll study it, and then if it makes economic sense for us to launch it, we'll do it." We kept asking them to take some of the lead (ballast) off and fly some of these things as secondaries, but they just didn't go along with it. I was really disappointed that the aerospace industry couldn't see the benefit other than profits from it. They couldn't see the educational benefit from it, and the potential of the educational benefit turning into commercial applications. Now, you see the commercial applications coming along with Skybox Imaging, with Planet Labs. Oh my goodness, they look like they have a tremendous economic potential.

Question: How much does it cost to build a CubeSat now?

Twiggs: If you get student labor, you do a 1U CubeSat, and if you scrounge a lot of parts, you could probably build one for about $50,000. But the problem you run into is the launch cost. Initially, when Cal Poly started their launch service, it was $40,000 to launch one and now it's anywhere from $80,000 to $125,000 to launch a 1U cubesat -- one 10-centimeter CubeSat. For the big boys, that's peanuts. But it isn't peanuts to us.

Question: How does someone get started in building a CubeSat?

Twiggs: It turns out there are quite a few vendors out there now that are building kits and building parts. If you can afford the parts, it's almost like a kit to put it together. If you can't afford that and you want to do stuff yourself, there's quite a bit of literature out on it. Before I built our first satellite, I'd never built any satellites before and never worked for an aerospace company. It was really a big mystery. But having built them now, I say that's not such a hard thing. Of course, that was after we built them. I think most of the universities are pretty good at it. Those who have built them, I think, are very open to providing some advice and help to those universities or organizations that have not built them.

The sad thing is there are a lot of students who want to do them, but they can't always find someone at the university to be their leader. If you can't have a faculty member that can support you, then it's awfully hard to do an independent project. You have to have a group of students who really have a passion to do it and support within the university.

Question: Do CubeSats make the space debris problem worse?

Twiggs: Right now, our requirement is before we launch, before we get a license from the Federal Communications Commission, we have to prove that the satellite is going to come down within 25 years.

A prototype PocketQube. Photo credit: Bob Twiggs
We did some analysis on the PocketQube because they go up to 700 kilometers. If you don't really do anything at 700 kilometers, these things could last for 100 years,and that's what they don't want. We did some analysis on it, and it turns out the PocketQubes at 700 kilometers would stay up over 30 years and did not meet the FCC requirements. We were able to put some things on the antenna that would increase the atmospheric drag on it and the calculations show it's going to come down in 17 years. We are actually able to reduce the space debris risk, and anything that goes off the International Space Station will come down within about a year.

Question: How is the PocketQube different from a CubeSat?

Twiggs: The standard dimension on a PocketQube is 5 centimeters, so it's essentially a 2-inch cube instead of a 4-inch cube.

Question: Does using the space station as a launch platform change the CubeSat market?

Twiggs: From my standpoint, I really like the ISS, especially for education because you get them launched and they're not going to stay up very long. I always said when building CubeSats that our goal was if we got it to a higher altitude and it had a long orbit life, we were thankful if it answered at all. If it worked pretty well, it would be great. If it operated for six months, that's even better. But if it operated for a year, everbody would be tired of it and quit using it.

The station, for what I want to to do, is an ideal launch platform. I think it's really great, and we're hoping with the PocketQube -- the PocketQube is one-eighth of a CubeSat -- we're developing a way to put these PocketQubes together so they have the same form factor as a CubeSat, and when we do that, theoretically, the launch costs should be one-eighth of what it is for a CubeSat and that might bring it down to $10,000 or $15,000, which opens up a lot of opportunities to do experiments. You don't have as much space, but look at what you get in a cellphone. My goodness, we aren't even scratching the surface of that with the technology in CubeSats now.

PREVIOUS PAGE: Twiggs recounts how CubeSats began

Follow Stephen Clark on Twitter: @StephenClark1.