Twenty years before modern spaceflight companies like SpaceX and Blue Origin began designing rockets that launch and land vertically, the DC-X had already done it.
Manufactured by McDonnell Douglas, the DC-X, short for Delta Clipper Experimental, was a single stage reusable rocket that was conceived to demonstrate the vertical takeoff and vertical land capability that was previously only possible in the realms of science fiction. Indeed, the DC-X looked something straight from the future. An elongated, white pyramid standing on four slender legs. It was only 12 meters tall, a dwarf among rockets.
The first test flight of the Delta Clipper-Experimental Advanced. Photo: NASA
The DC-X’s small stature is evidence that the rocket was never meant to reach orbital altitudes, but only to prove a concept, an idea that aerospace engineer Max Hunter had been nurturing for thirty years. Hunter wanted to design and built a single-stage-to-orbit (SSTO) vehicle, one that reached orbit without expending fuel tanks, engines, and other major hardware. In essence, a reusable rocket. Hunter was not the originator of the idea, but it was his former colleague Philip Bono, an engineer for Douglas Aircraft Company, who first proposed the concept. Bono designed a One-Stage Orbital Space Truck called OOST, a Recoverable One Stage Orbital Space Truck called ROOST, and a Reusable Orbital Module, Booster, and Utility Shuttle called ROMBUS. None of these progressed further than an idea on paper.
The first vehicle that came close to vertical takeoff, vertical landing (VTVL) was the two-stage Apollo Lunar Module. It landed vertically on the lunar surface, and then took off leaving the descent stage behind, so it was not a reusable rocket. The technology for building a truly reusable rocket didn’t exist then. But Hunter was intrigued by VTVL. For several years, he tried in vain to sell the idea to Lockheed Martin before he retired. In 1989, Hunter teamed up with science fiction author Jerry Pournelle and retired Army Lieutenant General Daniel O, and the trio was able to procure a meeting with Vice President Dan Quayle. They managed to convince the politician that the country’s defense lacked a reliable rocket that could be launched repeatedly and readied in the shortest possible time in between launches. Such a vehicle was essential in US’s arsenal should the country wanted to invest in space-based weapons system. With the uncertainties of Cold War looming over, the project was quickly approved and funded by the Strategic Defense Initiative Organization, the agency running the missile defense program.
Given the complexity of the project, Hunter and his team at McDonnell Douglas focused on creating a basic test vehicle that could demonstrate that a small crew could launch a spacecraft with lightning-fast turnaround times and at low cost. The final design was a one-third-size scale prototype, the Delta Clipper Experimental. On its maiden flight, on 18 August 1993, the craft took off from White Sands Missile Range in New Mexico, reached an altitude of 151 feet, hovered briefly, and still maintaining its vertical attitude, moved sideways for 350 feet. Then the engines throttled back in power, and the DC-X descended slowly and landed softly on its tail. The entire flight took only 59 seconds. It was the first time a rocket had landed vertically on Earth.
On successive tests, the Delta Clipper climbed higher and higher, until it reached a maximum altitude of 3 km, and each time it made perfect landing. By then, the program was taken over by NASA and had progressed to the second stage—the Delta Clipper Experimental Advanced, or DC-XA. The DC-XA demonstrated a 26-hour turnaround time, a record that is yet to be beaten.
Its 12th flight on July 31, 1996, proved to be its last. The rocket’s descent went off without a hitch, but as it approached the ground, a malfunction in the landing legs prevented one from deploying. Without the crucial support, the DC-XA fell over and exploded. The cost of a new Delta Clipper was USD 50 million, which wasn’t much by NASA standard, but NASA decided not to rebuild the craft anyway and instead began pursuing its own reusable launch idea, the Lockheed Martin X-33 VentureStar which was expected to replace the Space Shuttle. Eventually, VentureStar itself was cancelled because of development cost.
In recent years, private aerospace companies such as SpaceX and Blue Origin are spearheading the development in reusable rockets with VTVL capabilities. In 2013, SpaceX's Grasshopper rocket became the first privately build rocket to make a successful vertical landing after reaching an altitude of 744 meters. Two years later, Blue Origin's New Shepard booster rocket made the first-ever successful vertical landing after reaching space.
Two solid rocket boosters of SpaceX’s Falcon land at the Kennedy Space Center.
The VTVL fever is catching on. NASA is working on its own Project Morpheus, a VTVL vehicle using green propellent and autonomous landing and hazard detection technology. The German, French and Japanese space agencies are working together on a reusable VTVL rocket called CALLISTO. The Chinese private space company LinkSpace successfully tested its reusable experimental orbital rocket with a successful vertical takeoff, and India’s national space agency ISRO also announced they are developing a VTVL rocket.
References:
# Hailey Rose McLaughlin, DC-X: The NASA Rocket That Inspired SpaceX and Blue Origin, Discover Magazine
# Preston Lerner, Black Day at White Sands, Air & Space
# The Delta Clipper Experimental, NASA
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