X-33 space plane

Physical sample held up. Carbon-carbon composite with Nomex honeycomb at $12,000/lb.

[Tom holds up a composite sample.] This is a piece of the X-33 space plane liquid hydrogen tank. Carbon-carbon composite, Nomex honeycomb. That material cost twelve thousand dollars a pound. It's light, but at twelve thousand dollars a pound — as fabricated, a titanium submarine is only about a hundred times the cost of an HY-100 submarine. What are you paying for the hull of an HY-100 submarine right now? Probably twenty-five or thirty dollars a pound. So do you want to start paying three thousand bucks a pound to protect our subs? You can do it.

A $50M structure with manufacturing defects; NASA reduced the safety factor to 1.05 to keep the program alive; the tank passed at room temperature but failed on liquid-hydrogen thermal cycling. Used to illustrate that safety factors are not magic — they exist to absorb the manufacturing imperfections of real fabrication.

The X-33 spaceplane started out with a 2.0 safety factor. They had manufacturing problems — this was a fifty-million-dollar structure — and they knew they had some big defects in it. NASA sharpened their pencils and said, "Oh, we still got 5% safety factor above." They tested it, and it actually passed until they started to warm it up, and the thermal stresses from going from liquid hydrogen temperatures to room temperature — it failed because it didn't have enough safety factor. If it had been manufactured properly it may not have failed.

Used to illustrate how aerospace weight-savings drives composite adoption — and how the $12,000/lb fabrication cost of the composite liquid hydrogen tank ($50M for a 4,000-lb tank) killed the program. Tank size: "two-story house." Set up rapid-prototyping context from the first Gulf War.

In aerospace structures, an example of weight savings being critical to the whole structure is the X-33 spaceplane, which was supposed to replace the Space Shuttle. It was a $1.3 billion NASA project. The X-33 was a half-size vehicle, and it was going to fly all the way from Edwards Air Force Base to Dugway Proving Grounds in Utah. It was going to get up above a hundred miles, which makes it space, but it wasn't going to go around the Earth. It was just a demonstration vehicle. Before SpaceX came along, this was going to be a reusable vehicle. The Space Shuttle, as you remember, was not completely reusable — the main tanks were disposed of every time, and they tried to recover the solid rocket boosters. The actual thing that got up into space was a lot smaller. This whole thing would have gone into space.

[Tom holds up a composite sample.] This is part of the X-33 space plane, a composite material that cost about $12,500 a pound. So when you're talking about material selection, you have to talk about what industry you're in. If you're in the automotive industry or the railroad industry, they're not interested in twelve-thousand-dollar-a-pound composite structural materials. If you're in the aerospace industry or the spacecraft industry, they're cost-insensitive — they're performance-based, and they will pay a pretty penny because they can save $20,000 a pound. Actually they don't really save the $20,000; they can get an extra pound of payload up in space for the same rocket booster. That's just to give you some examples.

Physical sample shown to illustrate the $12,000/lb fabrication cost in aerospace.

Different industries value materials differently. Over the life of a vehicle, a pound saved in the automotive business is worth two dollars; in the commercial airplane business, two hundred dollars; in the aerospace industry, twenty thousand dollars. [Tom shows a piece of the X-33 space plane liquid hydrogen tank.] This is part of the shell — it's one of my prized possessions. This is part of the X-33 space plane liquid hydrogen tank, cost twelve thousand dollars a pound to fabricate, nice and light.

Tom uses the X-33 as the central morality tale of post-Gulf-War rapid prototyping. NASA awarded Lockheed Martin Skunk Works a $1.3B contract on a ~33-month schedule for a single-stage-to-orbit replacement for the Space Shuttle. The team spent six months designing a 3D-woven carbon composite ring-stiffened liquid hydrogen tank, discovered the design would blow the budget 4–5×, then improvised a Nextel-honeycomb / carbon-tape sandwich design in one month at $50M per tank, ~2,000 lb each. Cryogenic fill test at Huntsville appeared successful until video showed frost popping off — the carbon composite was permeable to hydrogen. Project cancelled; the tanks still sit at Palmdale. The X-33 piece passed around the class ($12,000/lb) anchors the cost-per-pound argument.

[Tom hands a piece of HY-80 around.] This is a piece of HY-80, made by our friends down there in Groton. You'll feel the weight and density. As-fabricated, that's probably two or three bucks a pound for the cost of what you're going to float or sink, as the case may be. [Tom hands a piece of X-33 composite around.] That is a piece of the X-33 space plane that cost $12,000 a pound for that composite. So you've got $2 a pound and you've got $12,000 a pound. But it's light, isn't it? It's not as strong and it's more brittle. It wouldn't do well in an explosion. But you can get things into space and still have some payload left over. You can afford it at $12,000 a pound. You could make an Indianapolis racer out of that material, but you can't afford to make a Ford Taurus out of it and sell it to anybody.

Brief mention as the would-be reusable-shuttle successor that "had problems." Foreshadowed for later lectures.

The space shuttle in the late 1960s was supposed to lower the price of a payload into orbit from $10,000 a pound to $1,000 a pound. How successful was the space shuttle? Well, it upped the price to about $300,000 a pound, because it had a few problems — but that's another story. It didn't meet its goal. Then there was the X-33 space plane that was supposed to give us a reusable space shuttle, and it had problems too. We'll tell you some of those stories in some of these other lectures. But you have to decide which modules you want to take.

Tom's extended case study of the failed $1.3B Lockheed Martin Skunk Works program. Used to teach: (1) rapid prototyping as a buzzword that can override engineering judgment; (2) how a 2.0 safety factor degraded to 1.05 through autoclave delamination; (3) how NASA misread the 3M epoxy data sheet (10% remaining strength after 10 days, not 80–90%); (4) the unverified hydrogen permeability number off by three orders of magnitude that became the final Achilles heel.

$12,000-per-pound composite hydrogen tanks, 8,000 lb total mass, $100 million total market — the limiting case for boutique-composite economics.

So one thing that gives material scientists a job is they get to try to figure out what the best material is. Composites are wonderful materials. I've shown you my $12,000-a-pound piece of the X-33 space plane. I've shown you this thing of the V-22 Osprey. They could not have built this without composites — graphite-epoxy composites. If they had made it out of something heavy like aluminum, they never could have gotten it to fly. It's the first large all-composite aircraft. They had made smaller little single- or two-person jets out of all composites, but the Osprey was the first one that was all composites.

The X-33 spaceplane was supposed to replace the space shuttle. They designed it for a 2.0. It was a 1.3 billion dollar program. The vessels that held the liquid hydrogen were about the size of a house — I have a piece of the composite material — very lightweight, size of a house, the basic structure weighed about 12,000 pounds. Very few houses are that lightweight, but this had to go in space. They had some problems with bonding of the carbon fiber and the Nomex honeycomb with the adhesive. They didn't want to cancel the program — it was a rush program in the early 90s to demonstrate rapid prototyping. So they just recalculated their safety factor and found out a 5 percent safety factor's good enough.

The lecture's flagship case study. Three failure modes braided: (1) the 3D woven graphite-fiber composite cost overrun that ate the budget before tanks were built; (2) the 10-day-shelf-life adhesive bullet point that hid a 100%→20% strength curve; (3) the post-test leak from CTE mismatch between graphite-epoxy, Nomex, and adhesive joints under cryogenic-to-room-temperature cycling. Outcome: $50M tanks scrapped, $1.3B program cancelled.

$1.3 billion half-size demonstrator. Two hydrogen tanks ($50M each composite) and one aluminum oxygen tank ($15M), totaling about $12,000/lb as fabricated. Intended successor to space shuttle, targeting $1,000/lb-to-orbit. Tank physical sample passed in class.

And this is the X-33 space plane. When you're going to twenty thousand dollars a pound for material into space — it always cost about ten thousand dollars a pound to get a pound of useful material into space. In the early 1970s, NASA had a goal to drop that to a thousand dollars a pound, and so they designed the space shuttle. The goal of the space shuttle was to drop the cost to about a thousand dollars a pound of useful material into orbit. So whenever you read about these things — any Course 16 folks in here? — they say, "Oh, we're going to colonize the moon, and we can send all the rich people to the moon." The only people who can afford ten thousand dollars a pound — it's going to cost $1.8 million to send an average person, just to get them there without their clothes or anything else. So there's a little problem with this "we're going to colonize Mars." It's because you haven't looked at the cost of these things.