DARPA’s Experimental Spaceplane (XS-1) program seeks to build and fly the first of an entirely new class of hypersonic aircraft that would break the cycle of escalating launch costs and make possible a host of critical national security options. As the next step toward a future of routine, responsive, and low-cost space access, DARPA has awarded Phases 2 and 3 of the program to The Boeing Company. (Credit: Boeing)

by Douglas Messier

Managing Editor

A couple of years ago, a friend made the surprising predication that DARPA’s Experimental Spaceplane Program (XSP) — a R&D effort designed to produce a rocket capable of being launched 10 times in 10 days — would never see any hardware built.

The reasoning went like this: the winning bidder, Boeing, really wasn’t interested in the technology. The company was actually interested in government funding and keeping other companies from developing the system.

The argument came from one of the losing bidders, so it was easy to take with a grain of salt. Still, it came as little surprise when DARPA announced today that Boeing was withdrawing from the program effectively immediately. Boeing’s winning entry, named the Phantom Express, had vanished into thin air.

Whether my friend was correct about Boeing’s lack of interest in the result is unclear. The decision came the week after a new CEO, Dave Calhoun, took over the reeling aerospace giant.

Boeing’s newest plane, 737 MAX, has been grounded for nearly 11 months after two fatal crashes caused by design problems. Return to flight has slipped to the middle of 2020. Some critics are calling for Boeing to abandon the jet all together. Plane orders slipped into negative numbers last year. And the company is reportedly seeking a $10 billion loan from banks to cover financial losses.

It wouldn’t be surprising if Calhoun was ordering programs cut so Boeing could focus its financial resources on more pressing priorities. XSP was structured as a public-private partnership that required Boeing to put up part of the funding.

In a statement, the company said the decision came after a detailed review.

“We will now redirect our investment from XSP to other Boeing programs that span the sea, air and space domains,” Boeing said. “We’re proud to have been part of a DARPA-led industry team that collaborated to advance launch-on-demand technology. We will make it a priority to harvest the significant learnings from this effort and apply them as Boeing continues to seek ways to provide future responsive, reusable access to space.”

XSP was intended to produce a suborbital rocket with an expendable second stage capable of being launched 10 times within 10 days. The technology would form the basis of a reusable orbital booster.

“The program sought to develop a launch system with aircraft-like operability, including flying on demand, the ability to rapidly and cost-effectively turn the system around between flights, a low ground infrastructure footprint, and low recurring costs,” DARPA said in its statement today.

The defense agency began the project, then known as XS-1, in 2013. The agency awarded phase 1 contracts to Boeing, Masten Space Systems and Northrop Grumman. In 2017, Boeing won the contract for the second and third phases that included $146 million in DARPA funding and an unspecified contribution by the company.

Boeing contracted with Aerojet Rocketydne to provide the company’s AR-22 engine to power the booster’s first stage. In 2018, engineers conducted ten static fires of the AR-22 in 10 days to demonstrate the engine was up to to the task.

Despite Boeing’s decision, DARPA tried to put a positive spin on the work that was accomplished during the program.

The detailed engineering activities conducted under the Experimental

Spaceplane Program affirmed that no technical showstoppers stand in the way of achieving DARPA’s objectives, and that a system such as XSP would bolster national security. Through XSP, DARPA identified evidence that present-day liquid rocket propulsion systems are capable of supporting XSP objectives, remain of interest, and may be explored in separate efforts.

The program yielded valuable data and accomplishments, including:

A liquid rocket vehicle configuration with operability and maintainability similar to an airplane

Detailed understanding of both civil and military mission

architectures well-suited for a system such as XSP

The environments and dynamics of deploying an upper stage carried in parallel with the booster

Design and fabrication of linerless composite tanks for cryogenic propellants

Successful completion of an AR-22 engine test program with a sequence of 10 discrete, long duration firings occurring within 10 days

Highly coupled design constraints associated with each phase of flight

A concept roadmap for different derived flight systems based on XSP technology.

This is the second DARPA-Boeing partnership to fail in recent years. The ALASA program sought to develop a small booster capable of launching a microsat into orbit from an unmodified F-15 fighter jet.

The program ended because the booster, powered by a mono-propellant, was prone to unplanned explosions.