National Aerospace Plane

Mid-1980s. 3mm copper skin, water-cooled, with liquid hydrogen fuel tank inside and 3000–4000°C frictional heating outside. Hydrogen-air contact at those temperatures = kaboom. Billions spent. Antecedent to the Air Force Mach 17 program.

They wanted to do this for the National Aerospace Plane in the mid-1980s. They were going to have about a three-millimeter-thick piece of copper — they'd use copper for thermal properties. They were going to have liquid hydrogen as the fuel tank, and they were going to have four-thousand-degree — or maybe it was three-thousand-degree — frictional heating in air on the outside. You want to rely on that? If you have a leak, what happens when hydrogen comes in contact with air at 3000 degrees centigrade? Kaboom. These people in the Air Force who dreamed these things up, they spent billions of dollars trying to design a National Aerospace Plane. They were going to do scramjets to get Mach 17 in air.

One-line dismissal alongside Star Wars as defense-fantasy money.

It's like the National Aerospace Plane — what a waste of money. These are the people who gave us things like Star Wars. Not that some things didn't come out of those, but not the product they were selling.

Mid-1980s program — Mach 17 spaceplane with copper skin (1/8-inch thick) cooled internally by liquid hydrogen against 3,000 K external air. Tom's framing: structurally absurd; partly a cover for Reagan-era Star Wars hardware-in-space.

It's just like for the National Aerospace Plane in the mid-80s. They wanted to develop the surface of the airplane coming back into the atmosphere. The National Aerospace Plane was supposed to be a supersonic transport. They would actually get up into space and then come back down, and it could be two and a half hours between any two cities on the globe, because you'd be going at Mach 17 up there in space. All you had to do was make the boost into space, do your travel with no air around, come back through the air, and land. This was actually partly — they never said it — but it was also part of Reagan's Star Wars initiative, because if you could put civilians up in space, you could put hardware up in space and weapons in space.

Reagan-era hypersonic vehicle proposal — liquid hydrogen tanks in the wings, copper alloy skin, 2,000 Kelvin skin temperature against 20 K hydrogen. Used to argue that materials selection has hard limits not negotiable by procurement ambition.

Anyone ever hear of the National Aerospace Plane? This was twenty, twenty-five years ago, just after the Reagan Star Wars defense buildup of the mid '80s. After they had designed the space shuttle, they decided they wanted to build a National Aerospace Plane to compete with the British Concorde. Anybody know what the Concorde is? It's out of business now. It was a supersonic commercial jet that would go from London to New York in less than five hours at about Mach 2.

Mid-80s proposal: copper skin 1–2 mm thick, liquid hydrogen on one side at 20 K, plasma on the other at 4–5,000 K. "As long as you didn't have a leak, everything was fine. If you ever had a leak, you have a big bomb."

They said, we can use things like active cooling. That was what they had proposed for the National Aerospace Plane back in the mid-80s. The National Aerospace Plane was going to be hydrogen-fueled, and they were going to make the skin out of copper, because it had great thermal conductivity. They were going to pump the liquid hydrogen through the skin, and the copper was going to be one or two millimeters thick. On one side you'd have four or five thousand degrees Kelvin, and on the other side you'd have liquid hydrogen at 20 degrees Kelvin. As long as you didn't have a leak, everything was fine. If you ever had a leak, you have a big bomb. So it wasn't a great design. But that's what the Air Force wanted to do.

Tom's service on an Air Force engine-research advisory committee (~2005) where the Mach 17 air-breathing strike requirement was justified by the bin Laden ordnance-reach problem. Used to teach the divergence of military and civilian engine technology, and the implausibility of the National Aerospace Plane copper-skin / liquid-hydrogen design.

I remember serving on a committee back in about this time frame that was looking at how the Air Force should spend its three hundred million dollars a year in research money for engine development. It was a very interesting committee — there were about 40 of us on it. Two of us were materials people. A number of people were from General Electric, the chief engineer on such-and-such engine. One guy sitting next to me was the guy who developed the F100 engine for Pratt & Whitney, I think that's right. There was a problem starting in the 1990s: military technology for engines diverged from civilian technology, and the civilians went to high-bypass engines. You know what high-bypass engines are? I'm seeing a lot of nods.