Function | Prototype SSTO vehicle |
---|---|
Manufacturer | McDonnell Douglas (Huntington Beach, California) |
Country of origin | United States |
Project cost | $60 million (1991) |
Size | |
Height | 12 metres (39 ft) |
Diameter | 4.1 metres (13 ft) |
Mass | 18,900 kilograms (41,700 lb) |
Stages | 1 |
Launch history | |
Status | Retired |
Launch sites | White Sands Missile Range |
Total launches | 12 |
Success(es) | 8 |
Failure(s) | 1 |
Partial failure(s) | 3 |
First flight | 18 August 1993 |
Last flight | 31 July 1996 |
First stage | |
Diameter | 4.1 metres (13 ft) |
Empty mass | 9,100 kilograms (20,100 lb) |
Gross mass | 18,900 kilograms (41,700 lb) |
Powered by | Four RL-10A-5 liquid-fueled rocket engines four gaseous oxygen/gaseous hydrogen thrusters |
Maximum thrust | Main rockets, 60 kN (13,000 lbf) Thrusters, 2.0 kN (440 lbf) |
Propellant | Liquid oxygen and liquid hydrogen |
The DC-X, short for Delta Clipper or Delta Clipper Experimental, was an uncrewed prototype of a reusable single-stage-to-orbit launch vehicle built by McDonnell Douglas in conjunction with the United States Department of Defense's Strategic Defense Initiative Organization (SDIO) from 1991 to 1993. Starting 1994 until 1995, testing continued through funding of the US civil space agency NASA. [1] In 1996, the DC-X technology was completely transferred to NASA, which upgraded the design for improved performance to create the DC-XA. After a test flight of DC-XA in 1996 resulted in a fire, the project was canceled. Despite its cancellation, the program inspired later reusable launch systems. Michael D. Griffin has since praised the program as "government R&D at its finest." [2]
According to writer Jerry Pournelle: "DC-X was conceived in my living room and sold to National Space Council Chairman Dan Quayle by General Graham, Max Hunter and me." According to Max Hunter, however, he had tried hard to convince Lockheed Martin of the concept's value for several years before he retired. [3] Hunter had written a paper in 1985 entitled "The Opportunity", detailing the concept of a Single-Stage-To-Orbit spacecraft built with low-cost "off-the-shelf" commercial parts and then available technology, [4] but Lockheed Martin was not interested enough to fund such a program themselves.
On February 15, 1989, Pournelle, Graham and Hunter were able to procure a meeting with Vice-President Dan Quayle. [5] They successfully "sold" the idea to SDIO by noting that any space-based weapons system would need to be serviced by a spacecraft that was far more reliable than the Space Shuttle, and offer lower launch costs and have much better turnaround times.[ citation needed ]
Given the uncertainties of the design, the basic plan was to produce a deliberately simple test vehicle and to "fly a little, break a little" in order to gain experience with fully reusable quick-turnaround spacecraft. As experience was gained with the vehicle, a larger prototype would be built first for sub-orbital and then orbital tests. Finally a commercially acceptable vehicle would be developed from these prototypes. In keeping with general aircraft terminology, they proposed the small prototype should be called the DC-X, X being the US Air Force designation for "experimental". This would be followed by the "DC-Y", with Y being the USAF designation for pre-production test aircraft and prototypes (e.g. YF-16). Finally the production version would be known as the "DC-1".[ citation needed ] The name "Delta Clipper" was chosen to result in the acronym "DC" to draw a connection with the Douglas "DC Series" of airliners, beginning with the Douglas DC-1.[ citation needed ]
The vehicle is inspired by the designs of McDonnell Douglas engineer Philip Bono, who saw single stage to orbit VTOL lifters as the future of space travel. [6] The Delta Clipper was very similar to Bono's SASSTO vehicle from 1967. Bono died less than three months before the DC-X's first test flight. [7]
SDIO wanted a "suborbital, recoverable rocket (SRR) capable of lifting up to 3,000 pounds (1361 kg) of payload to an altitude of 1.5 million feet (457 km); returning to the launch site for a precise soft landing; with the capability to launch for another mission within three to seven days". [8] : 4
DC-X Specifications: [9]
Built as a one-third-size scale prototype, [10] the DC-X was never designed to achieve orbital altitudes or velocity, but instead to demonstrate the concept of vertical take off and landing. The vertical take off and landing concept was popular in science fiction films from the 1950s ( Rocketship X-M , Destination Moon , and others), but not seen in real world designs of space vehicles. It would take off vertically like standard rockets, but also land vertically with the nose up. This design used attitude control thrusters and retro rockets to control the descent, allowing the craft to begin atmospheric entry nose-first, but then roll around and touch down on landing struts at its base. The craft could be refueled where it landed, and take off again from exactly the same position — a trait that allowed unprecedented turnaround times.
In theory a base-first re-entry profile would be easier to arrange. The base of the craft would already need some level of heat protection to survive the engine exhaust, so adding more protection would be easy enough. More importantly, the base of the craft is much larger than the nose area, leading to lower peak temperatures as the heat load is spread out over a larger area. Finally, this profile would not require the spacecraft to "flip around" for landing.[ citation needed ]
The military role made this infeasible, however. One desired safety requirement for any spacecraft is the ability to "abort once around", that is, to return for a landing after a single orbit. Since a typical low Earth orbit takes about 90 to 120 minutes, the Earth will rotate to the east about 20 to 30 degrees in that time; or for a launch from the southern United States, about 1,500 miles (2,400 km). If the spacecraft is launched to the east this does not present a problem, but for the polar orbits required of military spacecraft, when the orbit is complete the spacecraft overflies a point far to the west of the launch site. In order to land back at the launch site, the craft needs to have considerable cross-range maneuverability, something that is difficult to arrange with a large smooth surface. The Delta Clipper design thus used a nose-first re-entry with flat sides on the fuselage and large control flaps to provide the needed cross range capability. Experiments with the control of such a re-entry profile had never been tried, and were a major focus of the project.[ citation needed ]
Another focus of the DC-X project was minimized maintenance and ground support. To this end, the craft was highly automated and required only three people in its control center (two for flight operations and one for ground support).[ citation needed ]
Construction of the DC-X started in 1991 at McDonnell Douglas' Huntington Beach facility. [11] The aeroshell was custom-constructed by Scaled Composites, but the majority of the spacecraft was built from commercial off-the-shelf parts, including the engines and flight control systems.
The DC-X first flew, for 59 seconds, on 18 August 1993; [5] it was claimed that it was the first time a rocket had landed vertically on Earth. [12] It flew two more flights 11 September and 30 September, when funding ran out as a side effect of the winding down of the SDIO program; in addition the program was considered far-fetched by detractors. [13] Apollo astronaut Pete Conrad was at the ground-based controls for some flights. [14] These tests were conducted at the White Sands Missile Range in New Mexico. [15]
However, further funding was provided by NASA and the Advanced Research Projects Agency (ARPA). [1] The test program restarted on 20 June 1994 with a 136-second flight. The next flight, 27 June 1994, suffered a minor inflight explosion, but the craft successfully executed an abort and autoland. Testing restarted after this damage was fixed, and three more flights were carried out on 16 May 1995, 12 June, and 7 July. On the last flight a hard landing cracked the aeroshell. By this point funding for the program had already been cut, and there were no funds for the needed repairs. [16] The altitude record for the DC-X was 2,500 m, set during its last flight before being upgrading to the DC-XA, on 7 July 1995. [16]
NASA agreed to take on the program after the last DC-X flight in 1995. In contrast to the original concept of the DC-X demonstrator, NASA applied a series of major upgrades to test new technologies. In particular, the oxygen tank was replaced by a lightweight (alloy 1460 equivalent of alloy 2219) aluminium-lithium alloy tank from Russia, and the hydrogen tank by a graphite-epoxy composite design. [17] The control system was likewise improved. The upgraded vehicle was called the DC-XA, renamed the Clipper Advanced/Clipper Graham, and resumed flight in 1996. [5]
The first flight of the DC-XA test vehicle was made on 18 May 1996 and resulted in a minor fire when the deliberate "slow landing" resulted in overheating of the aeroshell. The damage was quickly repaired and the vehicle flew two more times on 7 and 8 June, a 26-hour turnaround. [5] On the second of these flights the vehicle set its altitude and duration records, 3,140 metres (10,300 ft) and 142 seconds of flight time. Also, during the 8 June flight, the vehicle executed the first planned rotation maneuver for a rocket, where it transitioned from nose first forward flight to controlled backwards flight. At the apex of this rotation maneuver, DC-XA slowed itself by rotating to a backwards orientation, and flew backwards, base first, with its nose 10 degrees below the horizon, under control of the main engines. It then exercised a controlled rotation to a nose up attitude, and executed a powered soft landing. This maneuver showed that a single stage to orbit vehicle could efficiently return from orbit using aerodynamic braking in a forward attitude, and then rotate to a base first powered landing at a spaceport.[ citation needed ]
Its next flight, on 31 July 1996, proved to be its last. The launch and flight portion of this mission was flawless, however, after slowing to a perfect touchdown, only 3 of the 4 landing struts extended. The vehicle could not balance on 3 struts, and slowly fell sideways on the landing pad. When the side of the vehicle struck the concrete pad, the main liquid oxygen tank cracked open and leaked LOX onto the pad. This LOX contacted a small amount of glowing material on the base heat shield, and started a fire. Post flight inspection of the landing struts revealed that the pneumatic nitrogen actuation line to the failed strut was disconnected. This line was normally disconnected from the strut during pre-flight testing, when each strut was extended and retracted by a ground cart. Normally the structural damage from such a fall would constitute only a setback, but the LOX from the leaking tank fed a fire which severely burned the DC-XA, [18] causing such extensive damage that repairs were impractical. [16]
In a post-accident report, NASA's Brand Commission blamed the accident on a burnt-out field crew who had been operating under on-again/off-again funding and constant threats of outright cancellation. The crew, many of them originally from the SDIO program, were also highly critical of NASA's "chilling" effect on the program, and the masses of paperwork NASA demanded as part of the testing regimen.[ citation needed ]
NASA had taken on the project grudgingly after having been "shamed" by its very public success under the direction of the SDIO.[ citation needed ] Its continued success was cause for considerable political in-fighting within NASA due to it competing with their "home grown" Lockheed Martin X-33/VentureStar project. Pete Conrad priced a new DC-X at $50 million, cheap by NASA standards, but NASA decided not to rebuild the craft in light of budget constraints. [16] Instead, NASA focused development on the Lockheed Martin VentureStar which it felt answered some criticisms of the DC-X, specifically the airplane-like landing of the VentureStar, which many NASA engineers preferred over the vertical landing of the DC-X. Just a few years later, the repeated failure of the Venturestar project, especially the composite LH2 (liquid hydrogen) tank, led to program cancellation. [19]
The original DC-X was built in 21 months for a cost of $60 million. [20] This is equivalent to $120 million in present-day terms. [21]
Several engineers who worked on the DC-X were hired by Blue Origin, and their New Shepard vehicle was inspired by the DC-X design. [22] The DC-X provided inspiration for many elements of Armadillo Aerospace's, [5] Masten Space Systems's, [5] and TGV Rockets's spacecraft designs.[ citation needed ] Elon Musk stated that the SpaceX Falcon 9 development was "... continuing the great work of the DC-X project." [23]
Some NASA engineers have noted that the DC-X could provide a solution for a crewed Mars lander. [24] Had a DC-type craft been developed that operated as an SSTO in Earth's gravity well, even if with only a minimum 4–6 crew capacity, variants of it might prove extremely capable for both Mars and Moon missions. Such a variant's basic operation would have to be "reversed"; from taking off and then landing, to landing first then taking off. Yet, if this could be accomplished on Earth, the weaker gravity found at both Mars and the Moon would make for dramatically greater payload capabilities, particularly at the latter destination.[ citation needed ]
Some people proposed design changes include using an oxidizer/fuel combination that does not require the relatively extensive ground support required for the liquid hydrogen and liquid oxygen that DC-X utilized, and adding a fifth leg for increased stability during and after landing.[ citation needed ]
A single-stage-to-orbit (SSTO) vehicle reaches orbit from the surface of a body using only propellants and fluids and without expending tanks, engines, or other major hardware. The term exclusively refers to reusable vehicles. To date, no Earth-launched SSTO launch vehicles have ever been flown; orbital launches from Earth have been performed by either fully or partially expendable multi-stage rockets.
A lifting body is a fixed-wing aircraft or spacecraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage with little or no conventional wing. Whereas a flying wing seeks to maximize cruise efficiency at subsonic speeds by eliminating non-lifting surfaces, lifting bodies generally minimize the drag and structure of a wing for subsonic, supersonic and hypersonic flight, or spacecraft re-entry. All of these flight regimes pose challenges for proper flight safety.
Armadillo Aerospace was an aerospace startup company based in Mesquite, Texas. Its initial goal was to build a crewed suborbital spacecraft capable of space tourism, and it had also stated long-term ambitions of orbital spaceflight. The company was founded by John Carmack, co-founder and former chief technical officer of id Software.
Human spaceflight programs have been conducted, started, or planned by multiple countries and companies. Until the 21st century, human spaceflight programs were sponsored exclusively by governments, through either the military or civilian space agencies. With the launch of the privately funded SpaceShipOne in 2004, a new category of human spaceflight programs – commercial human spaceflight – arrived. By the end of 2022, three countries and one private company (SpaceX) had successfully launched humans to Earth orbit, and two private companies had launched humans on a suborbital trajectory.
A reusable launch vehicle has parts that can be recovered and reflown, while carrying payloads from the surface to outer space. Rocket stages are the most common launch vehicle parts aimed for reuse. Smaller parts such as rocket engines and boosters can also be reused, though reusable spacecraft may be launched on top of an expendable launch vehicle. Reusable launch vehicles do not need to make these parts for each launch, therefore reducing its launch cost significantly. However, these benefits are diminished by the cost of recovery and refurbishment.
A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes tend to be more similar to conventional spacecraft, while sub-orbital spaceplanes tend to be more similar to fixed-wing aircraft. All spaceplanes to date have been rocket-powered for takeoff and climb, but have then landed as unpowered gliders.
The Lockheed Martin X-33 was a proposed uncrewed, sub-scale technology demonstrator suborbital spaceplane that was developed for a period in the 1990s. The X-33 was a technology demonstrator for the VentureStar orbital spaceplane, which was planned to be a next-generation, commercially operated reusable launch vehicle. The X-33 would flight-test a range of technologies that NASA believed it needed for single-stage-to-orbit reusable launch vehicles, such as metallic thermal protection systems, composite cryogenic fuel tanks for liquid hydrogen, the aerospike engine, autonomous (uncrewed) flight control, rapid flight turn-around times through streamlined operations, and its lifting body aerodynamics.
Dream Chaser is an American reusable lifting-body spaceplane developed by Sierra Space. Originally intended as a crewed vehicle, the Dream Chaser Space System is set to be produced after the Dream Chaser Cargo System cargo variant is operational. The crewed variant is planned to carry up to seven people and cargo to and from low Earth orbit. Sierra plans to manufacture a fleet of the spaceplane.
A launch vehicle is typically a rocket-powered vehicle designed to carry a payload from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage rocket, but the term is more general and also encompasses vehicles like the Space Shuttle. Most launch vehicles operate from a launch pad, supported by a launch control center and systems such as vehicle assembly and fueling. Launch vehicles are engineered with advanced aerodynamics and technologies, which contribute to high operating costs.
Philip Bono was a Douglas Aircraft Company engineer. He was a pioneer of reusable vertical landing single-stage to orbit launch vehicles. As a visionary designer, he is credited with inventing the first version of a recoverable single-stage spacecraft booster, and his contributions influenced spacecraft design.
Daniel Orrin Graham was a United States Army officer who ultimately rose to the rank of lieutenant general. Graham served in Germany, Korea, and Vietnam and received several decorations including some of the highest the United States military bestows: the Distinguished Service Medal, the Legion of Merit with two oak leaf clusters, and the Distinguished Intelligence Medal during his distinguished 30-year military career.
Before the Apollo 11 Moon landing in 1969, NASA began studies of Space Shuttle designs as early as October 1968. The early studies were denoted "Phase A", and in June 1970, "Phase B", which were more detailed and specific. The primary intended use of the Phase A Space Shuttle was supporting the future space station, ferrying a minimum crew of four and about 20,000 pounds (9,100 kg) of cargo, and being able to be rapidly turned around for future flights, with larger payloads like space station modules being lifted by the Saturn V.
Maxwell White Hunter II was a prominent American aerospace engineer. He worked on the design of the Douglas B-42 and Douglas B-43 bombers, the Honest John, Nike-Ajax, and Nike-Zeus missiles, the Thor IRBM, and on parts of the Strategic Defense Initiative. In later years he worked on space-launch vehicles and was a proponent of Single-stage-to-orbit (SSTO) designs. He was honored in 1995 by the National Space Society for lifelong contributions to the technology of spaceflight.
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An aeroshell is a rigid heat-shielded shell that helps decelerate and protects a spacecraft vehicle from pressure, heat, and possible debris created by drag during atmospheric entry. Its main components consist of a heat shield and a back shell. The heat shield absorbs heat caused by air compression in front of the spacecraft during its atmospheric entry. The back shell carries the load being delivered, along with important components such as a parachute, rocket engines, and monitoring electronics like an inertial measurement unit that monitors the orientation of the shell during parachute-slowed descent.
Not to be confused with the successful civilian airliner, the Douglas DC-3
The Lockheed Star Clipper was a proposed Earth-to-orbit spaceplane based on a large lifting body spacecraft and a wrap-around drop tank. Originally proposed during a United States Air Force program in 1966, the basic Star Clipper concept lived on during the early years of the NASA Space Shuttle program, and as that project evolved, in a variety of new versions like the LS-200.