It has taken until the second decade of the 21st century, but the U.S. government has finally designated space to be a legitimate domain of military operations and has stood up the U.S. Space Force — that’s the good news. The not-so-good news is that the U.S. Space Force has no routine, reliable access to space.
Single-Stage-To-Orbit (SSTO) Reusable Launch Vehicle (RLV) releasing a satellite into orbit.
The Space Force will operate in the near-Earth and cislunar domains like our current military operates in the domains of land, sea, and air. The Army and Marines have their land and air vehicles, the Navy has its surface ships and submarines, and the Air Force has its airplanes. But the assets being transferred to the Space Force — satellites and expendable launch vehicles — are akin to lighthouses, buoys, dirigibles, and coastal artillery because we have so far only treated space as a support service.
The U.S. Space Force must acquire responsive, routine, and reliable access to space — starting with launch systems optimize for reaching low Earth orbit (LEO). The Space Force must be equipped with a fleet of responsive, spacefaring vehicles under the operational purview of the Space Force’s equivalent of an Air Force colonel or Navy captain. Currently, the resource requirements for space launch are so large that only a three-star general of above to approve a mission; for launch to be truly operationally responsive, the required resources — and decision-making authority — must be driven down to a level comparable to what’s been required to send a B-2 Stealth Bomber or the now-retired SR-71 reconnaissance aircraft aloft.
Many space analysts agree that this capability needs reusable launch vehicles (RLVs), not the current multi-stage, expendable vehicles. The only way to reduce the sortie cost down to a minimum marginal cost would be with reusable single-stage-to-orbit (SSTO) vehicles, i.e., one-piece spaceships. Improved technology and a focus on operability are required to move to single-stage reusables from two-stage expendables.
Reusability has been demonstrated many times. Most famously, NASA’s space shuttle flew for 30 years. In the past five years, SpaceX has commercially launched, landed and reused Falcon 9 first stages many times now.
Reagan’s Strategic Defense Initiative Office (SDIO) looked hard at coming up with a reusable SSTO. They succeeded in identifying what are still key challenges: advanced structural engineering; challenging vehicle control; soft vertical takeoff/vertical landing (VTVL); and operability. For a total program cost of $100 million, SDIO flew the McDonnell-Douglas DC-X, a 1/10th scale VTVL ship, to 35,000 feet and demonstrated wingless maneuvering, soft VTVL, and operability with enlisted personnel.
In the 1990s, NASA identified three critical technology needed to make an SSTO spacecraft achievable:
(1) advanced composite materials;
(2) altitude compensating engines; and
(3) tri-propellant engines.
The required advanced composites materials have largely been developed over the
past 25 years, as witness the improved aluminum alloys and more advanced carbon composites now available. The altitude-compensating engines are needed to so that one engine can both take off in the atmosphere and make orbit in a vacuum. NASA made progress on this with the one-third scale Lockheed Martin X-33 and the Air Force Research Laboratory (AFRL) is currently investigating aerospike nozzles with the Affordable Responsive Modular Rocket (ARMR) Program. What has been lacking is the tri-propellant propulsion technology for SSTO-RLVs.
Entrepreneurial firms, such as TGV, have proposed novel approaches to the challenges of an SSTO-RLV. These innovations include new ways of approaching a tri-propellant engine, novel engine nozzles for altitude compensation, and new launch sites for more flexibility. Engineering for reliability, deep throttling, landing, and imaginative systems engineering are currently needed to improve the mass fraction and operability of a practical SSTO-RLV. These technologies are ready to be developed and brought into routine use in a reasonable time frame.
The Space Force, in developing their spaceships, will need to focus on the four pillars of responsive launch: operability, reliability, affordability and dispatchability. To get the ball rolling, the U.S. Defense Department should leverage existing AFRL research on building better performing engine systems and other innovative approaches to improve the engineering necessary for fielding an SSTO test vehicle.
The Space Force needs routine access to space; it needs spaceships. It needs a credible SSTO capability as soon as possible to claim its place in the domain. We can achieve practical SSTOs with the expenditure of a relatively small amount of additional R&D dollars aimed at the right technologies and toward a flying prototype. If we spend a few bucks, we can and will achieve the ‘Buck Rogers’ spaceship.
Pat Bahn is the CEO of TGV Rockets Inc., a merchant provider of liquid propulsion. Tim Kyger is an independent space analyst and former congressional professional staffer.
