The Space Plane NASA Wanted to Use to Build Solar Power Plants in Orbit
Image: Boeing

The Space Plane NASA Wanted to Use to Build Solar Power Plants in Orbit

1970s space dreaming at its finest: The massive Star-Raker space plane would take carry solar power satellites into orbit.
September 21, 2015, 2:08pm

At the height of the oil crisis in the 1970s, the US government considered building a network of 60 orbiting solar power stations that would beam energy down to Earth. Each geosynchronous satellite, according to this 1981 NASA memo, was to weigh around 35,000 to 50,000 metric tons. The Satellite Power System (SPS) project envisaged building two satellites a year for 30 years.

A NASA depiction of two competing Solar Power Satellite designs.

There was just one problem: How do you launch more than 70,000 metric tons of cargo into orbit every year, when the Space Shuttle's maximum payload was around 25 metric tons—and then only to low-earth orbit? Even if you launched 200 metric tons into orbit every single day of the year, you'd still fall behind. And there were never more than half a dozen Space Shuttles, anyway.

Enter the Star-Raker.

Image: BoeingImages.com

Designed but never built by the now-defunct Rockwell International, the proposed Star-Raker would load its cargo at a regular airport, fly to a spaceport near the equator, fuel up on liquid oxygen and hydrogen, and take off horizontally using its ten supersonic ramjet engines. A 1979 technical paper lays out its potential flight plan: At a cruising altitude of 45,000 feet, the craft would then dive to 37,000 feet to break the sound barrier. At speeds of up to Mach 6, the Star-Raker would jet to an altitude of 29km before the rockets kicked in, propelling it into orbit.

Image: BoeingImages.com

Each Star-Raker was projected to carry a payload of 100 tons, and a fleet of Star-Rakers would work day-in, day-out to shuttle into orbit the materials and tools and astronauts required to assemble these massive satellites.

A NASA depiction of what a Solar Power Satellite would look like.

"The magnitude and sustained nature of this advanced space transportation program concept requires long-term routine operations somewhat analogous to commercial airline/airfreight operations," NASA wrote in the 1981 memo.

A 747 into space, in other words.

Image: BoeingImages.com

Pitched by Rockwell as an "Airbreather/Rocket-Powered, Horizontal Takeoff Tridelta Flying Wing, Single-Stage-To-Orbit Transportation System," the Star-Raker left quite an impression on its audience.

"The SPS is an attractive, challenging, worthy project, which the aerospace community is well prepared and able to address," physicist Robert G. Jahn wrote in the foreword to a 1980 SPS feasibility report. "The mature confidence and authority of...[the working groups]...left the clear impression that if some persuasive constellation of purposes...should assign this particular energy strategy a high priority, it could be accomplished."

Image: BoeingImages.com

The same report goes on to describe the Star-Raker as the most advanced concept proposed. The Star-Raker, it states, "represents the direct thrust of future aerospace development...it is necessary that the essential technologies be pursued actively."

President Carter was probably interested in the SPS. In his famous April 18, 1977 address, he forecast a catastrophe if alternatives to fossil fuels were not found. "We must start now to develop the new, unconventional sources of energy we will rely on in the next century," he told the American people.

That persuasive constellation of purposes never aligned. The Star-Raker never got built, nor did the Satellite Power System. But given the promise of catastrophic climate change the world is now facing, we can't help but wonder what might have been.

Image: BoeingImages.com