Experimental Spaceplanes

Experimental Spaceplanes

The most notable space plane is most likely the United States Space Shuttle. There are however more spaceplanes that have been in development and even flew. Think of the Soviet Buran, the X-20 dyna-soar and the upcoming Dream Chaser. To make these missions possible many demonstrator missions have been flown. This page gives an overview of the different missions that flew in support of spaceplanes. For an overview of planned or operational space planes can be found here.


Operator: NASA, ESA, DLR

Mission: Crew return vehicle

First flight: Unflown 

Status: Cancelled

The X-38 was an experimental NASA vehicle that could be launched on an Ariane 5 launcher. The project was cancelled in 2002. The launching on top of the Ariane 5 reminds one of the Hermes spacecraft, which was cancelled in 1987. Later, the X-38 research was used in the Crew Return Vehicle (CRV). The CRV would be used if a fast evacuation of the international space station (ISS) would be required. The X-38 would have used a 100 ft drogue parachute and a parafoil main parachute, much like the Space Rider.

A backup parachute system was designed to safely land the vehicle in case of an emergency. This system contained a hybrid continuous ribbon-ringslot main parachute of 36.6 m diameter and a 7.9 m ribbon drogue parachute. The pilot chute and mortar of the backup system were identical to that of the primary recovery system and nearly identical to that of the Space Shuttle brake chute system.

A sub-scale version of the parachute was tested during drop tests where the parachute’s performance and new manufacturing methods were evaluated. The X-38 program was eventually cancelled in 2002, however, the parachute system lived on. The design was transferred to the US army’s LVAD program (Low-Velocity AirDrop system), where it would be used to land equipment from aircraft. Several tests showed skirt inversion and canopy inflation, likely caused by the high angle of attack encountered by the parachute when the payload is dropped out of the aircraft, in combination with the downwash. A temporary reefing system eventually solved the problem. [24, 25, 26]

Parafoil landing of the X-38, drop test

HYFLEX - Hypersonic FLight EXperiment

Operator: NASDA

Mission: Winged Re-Entry demonstrator

Flight: 1996

Status: Completed

Testing for: HOPE

In the ‘90s and early ‘00s, Japan had several research programs running to develop the necessary technology readiness to launch a reusable, orbit-capable space plane called HOPE. After the success of the OREX capsule re-entry experiment in 1994, the HYFLEX mission flew in 1996. In contrast to the ballistic OREX capsule, HYFLEX used a steerable, lifting body configuration during re-entry. The ALFLEX vehicle was flown in the years after HYFLEX to prove the technological capabilities for autonomous landing, subsonic flight and transonic flight for the HOPE spaceplane (see ALFLEX and HSFD). 

The vehicle was 4.4 meters long, weighed 1054 kg and featured two small, tilted wings near the rear of the vehicle. Attitude control was provided by two aerodynamic flaps and a series of RCS thrusters for control outside of the atmosphere. Three types of thermal protection were included: a carbon-carbon heat shield,  ceramic tiles and a flexible insulator.

In February 1996, HYFLEX was launched aboard the J-I rocket. The flight proceeded nominally and all data was transmitted to the ground station. However, after the splashdown in the ocean, a flotation system failure occurred, causing an unsuccessful recovery and loss of the vehicle. Apart from the failed retrieval, the mission was a success and improved Japan’s technology readiness regarding lifting body re-entry. [64, 65]



RLV-TD - Reusable Launch Vehicle

Operator: ISRO

Mission: Winged Re-Entry demonstrator

Flight: -

Status: In development

Testing for: RLV

ISRO's RLV is a project that aims to develop a reusable launch vehicle that can reduce the cost and increase the frequency of space missions for India. The RLV is envisioned to be a two-stage-to-orbit (TSTO) vehicle that can launch satellites into orbit and return to Earth for reuse. The RLV consists of a winged orbiter and a booster stage. ISRO has been testing various technologies related to the RLV through a series of experimental flights.

The first flight, called RLV-TD HEX-01, was conducted in 2016 and demonstrated the hypersonic flight and re-entry capabilities of the vehicle. It was launched on top of a solid rocket booster and reached an altitude of about 65 km. Then, it separated from the booster and glided back to Earth, performing various manoeuvres to test its aerodynamics and control systems. It splashed down in the Bay of Bengal, about 450 km from the launch site. The flight lasted for about 13 minutes and was deemed a success.

The second flight, called RLV-TD LEX, was conducted in 2023 and demonstrated the autonomous landing capability of the orbiter on a runway. The RLV-TD, was released from a helicopter at an altitude of 4.6 km and landed safely on a runway using its own guidance and control systems. 

The third flight, planned for 2024, will demonstrate the powered cruise flight capability of the orbiter using an air-breathing scramjet engine.

The launch of ISRO's RLV-TD HEX-01
ISRO's RLV-TD LEX during the landing

ISRO's RLV during the HEX-01 flight (right) and the LEX test (left). 

The RLV project is a landmark moment in India's space history as it showcases the country's technological prowess and innovation in developing a low-cost and eco-friendly launch system. The RLV will also enable ISRO to launch more satellites for various applications such as communication, navigation, remote sensing and scientific exploration.


Operator: USAF

Mission: Aerothermodynamic and structural testing for winged-body vehicles

Flight: 6 flights (1963-1965)

Status: Completed

When the X-20 Dyna-soar was cancelled without flying the hardware, a new program was created to achieve the goals. This project was the Aerothermodynamic elastic Structural Systems Environmental Tests, or simply named ASSET. Besides testing the heatshield created for the Dyna-soar, the ASSET program also aimed to test flutter behaviour in hypersonic speeds, control during hypersonic speeds using a trailing edge flap and study materials and structures in a re-entry environment [48,49].

Two versions were created, the aerothermodynamics structural vehicle (ASV) and the aerothermodynamic elastic vehicle (AEV). The two versions split the goals with the AEV studying the flutter and control and ASV studying the materials and structures in re-entry environments. Both ASSET vehicles had a height of 1.79 m and a wingspan of 1.53 m [5.]. It had an L/D between 1.2 and 1.4 controlled by a weight that is moved internally [48]. The ASV had a mass of 512 kg and the AEV 555 kg. Another difference between the two vehicles is for the ASV had a parachute recovery system, but the details are unknown, the AEV because of the extra support equipment had no recovery system on board [50].

All ASSET vehicles were launched with variants of the Thor launch vehicle. The AEV was launched on the standard Thor launcher. The ASVs were launched on the Thor-delta. This difference was to increase the re-entry velocity of the ASVs (5-6 km/s) to the AEVs (4km/s) [52]. This ensured the ASVs had a temperature in excess of 2200 C on the nose cap [49,51].

Of the six flights flown two were with an AEV vehicle and four with an ASV vehicle. As previously mentioned the AEV did not have a recovery system and were designed to be lost after the flight. Of the four ASV flights, only one vehicle (ASV-3) was successfully recovered [49]. Of the three vehicles that were lost, one was due to the second stage of the launcher that failed to ignite (ASV-2), another sunk after the flotation system failed (ASV-1) and one was lost due to a parachute failure (ASV-4) [49]. However, except for ASV-3 good telemetry data was received and these flights were judged as a success. The data gathered during the ASSET program eventually would be used to design the space shuttle.




Operator: USAF

Mission: Structural, heating, and manoeuvring research during re-entry

Flight: 3 flights (1966-1967)

Status: Completed

During the mid-1960s the US-Air Force started the PRIME program. This program had the goal to test various elements during the hyper- and supersonic flight regimes. The goals were to test the structure and the heat shield. But the main goal of the, at the time a classified goal, was to test the manoeuvrability during the re-entry [45]. The goal was to be able to have a cross-range manoeuvrability up to 1100km from the target, which was for the retrieval of data from space.

The vehicle itself was a 403 kg lifting body re-entry vehicle made mostly out of aluminium [47]. It was about 2 m long and 0.8 m wide and had a lightweight phenolic ablative heatshield between 20-70mm thick [45]. Once the vehicle was back in the atmosphere it deployed a 1.46 m ballute drogue parachute using a parachute mortar [47]. Afterwards is deployed the 14.3 m main parachute, which was an extended skirt type with an air pick-up cone [47]. The vehicle was recovered in mid-air using a specially equipped JC-130B Hercules [44]. If for some reason the vehicle was not picked up by the recovery aeroplane it also had the capability to land in the ocean. For this floatation bags were installed [47].

In total 4 flights were planned at the start of the program with only 3 being completed [46]. The fourth flight was a backup flight for when one of the first three flights were unsuccessful. This was not the case. However, of the three flights that were flown two of the three vehicles were lost in the ocean. All data was sent down, therefore these flights were still qualified as a partial success. As all goals were achieved.


PRIME pre-flight


Operator: USSR

Mission: Spaceplane development/ prototype for Buran

Flight: 1969-1988

Status: Completed

A month before Apollo 11 lifted off, in 1969, a Cosmos-3 launcher lifted off carrying an 800 kg and 3m long, BOR-1 vehicle. This vehicle, which is similar in shape but not in size to the Dream Chaser and the X-38, was the first attempt by the soviet union to gain practical experience in space planes for the Spiral project. The Spiral project fulfilled a need the soviet air force had of hypersonic orbital aircraft.

The BOR-1 vehicle, a 1:3 scaled version of the eventual capsule on top of the Spiral vehicle, reached an altitude of 100 km as planned on its first mission. However, when it re-entered the atmosphere at 3.6 km/s, the heat reached every part of the outer surface. When it landed, all surfaces were found to be burned. However, it still transmitted its trajectory information up to 60-70km.

After this, the investigation of space planes continued with the BOR-2 and BOR-3 vehicles. With the BOR-2 vehicle having improvements on its thermal protection system and the BOR-3 being scaled up in size, being a 1:2 scaled version of the final Spiral project vehicle. The BOR-2 flew four times, of which all were successful. BOR-3 flew twice. Both times an issue occurred. The nose fairing was destroyed during the first flight when flying at about 5km with Mach 0.94. The flight program was fully implemented on the second flight, but due to a parachute failure, the vehicle crashed.

Bor 3



During the seven missions, the vehicle had good stability and manoeuvrability. But unfortunately, the Spiral program was cancelled in favour of the Buran program. However, more investigation was needed for the Buran program on the heat shield, which consisted of various materials: quartz fibre tiles and a carbon-carbon nosecone. For this, the BOR-4 vehicles were used. However, compared to BOR-3, BOR-4 vehicles were intended to orbit, circle the earth once, and re-enter and land. Seven BOR-4 vehicles were produced, of which one flew a suborbital flight, and four others went into orbit. All four successfully splashdown. However, one BOR-4 was lost in the black sea before retrieval.

Because the BOR-4 vehicles were aerodynamically different from the Buran vehicle, it could not be used to validate the aerodynamics for Buran. The BOR-5 vehicle was created, a 1:8 scaled model of the Buran orbiter weighing 1450 kg to validate this aspect of the Buran orbiter. Besides the aerodynamics also the thermal protection and vibrational loads were measured.

The BOR-5 vehicles, as BOR-1/2/3, were suborbital vehicles, which were launched to a maximum altitude of 210 km. After which, it re-entered and landed with a velocity of 7-8 m/s using a parachute in Lake Balkhash. Five flights were flown, of which only the first was unsuccessful with the vehicle failing to separate from the launcher. Half a year after the last flight of the BOR-5 vehicle, the Buran launcher lifted off from Baikonur.

After the BOR-5, the focus was again put on the Spiral shape with BOR-6. However, the BOR program was cancelled before this came to anything. [54,55,56,57,58,59].