Manoeuvring Reentry test vehicles 

During the Cold War, there was a continuous race between the USSR and United States to technologically outperform each other's long-range missiles. As the anti-ballistic missile systems became more capable over time, there was a need to develop long-range missiles that could manoeuvre during reentry. This created a cat-and-mouse game of increasingly advanced reentry vehicles and countermeasures. In the United States, many technology demonstrator missions were flown to mature the technology from the late '50s onward. Although the Anti-Ballistic Missile treaty in 1972 has limited the development of such missile systems, research towards reentry manoeuvrability has never fully stopped. Even though the large majority of the manoeuvring reentry vehicles were designed for military applications, much of the technology eventually found its way into the civilian space industry. 

Two solid rocket motors, a TX-20 and TX-30, propelled the vehicle high in the atmosphere to speeds over Mach 5. This was followed by a gliding phase where the conical body was spinning around its axis at a small angle of attack to provide the necessary lift force and distribute the aerothermal heating. By gliding towards its target, the missile could cover a larger distance than a purely ballistic equivalent. This vehicle had a diameter of 0.79 m, was 4.293 m long, and weighed 136.08 kg. Its sharp conical nose with half angle of 5.36° and small nose radius of 2.54 cm allowed it to experience a relatively high lift-to-drag ratio of 3.5 during its glide phase. [136]

Eventually three Alpha Draco rockets flew, launched from Cape Canaveral, all in 1959. The first and second flight, launched on February 16th and March 16th, were both successful and proved that the concept of a boost-glide vehicle was feasible. The third flight however encountered a malfunction causing the vehicle to veer off course, requiring a flight termination by range safety. [136]

The flight trajectory that was proven possible by Alpha Draco was called ‘boost-glide reentry’ and would later be further improved by the BGRV (Boost Glide Reentry Vehicle) project during the late ‘60s. Through the Alpha Draco flights, engineers were able to obtain valuable data on the thermal and aerodynamic characteristics of hypersonic flight, which would later be used to validate wind tunnel data and design other high-speed reentry vehicles.

During the late ‘50s, both the United States and USSR saw the potential of gliding reentry vehicles to extend the range of the more conventional ballistic missiles. In 1957, the USSR’s Tupolev bureau started the development of a boost-glide reentry vehicle that would be able to glide to its target at hypersonic speeds and then dive down to strike. It was the same year that the US Air Force also started the work on a boost-glide reentry vehicle for the first time, namely the Alpha Draco.

After two years of research, developments, and flight testing, the program was cancelled  before the vehicle reached an operational status. There was a preference towards the Tu-123 supersonic cruise missile, which could fulfil the same purpose. The research and new technologies of the Tu-130 however laid the foundation for the USSR’s future hypersonic flight vehicles and were incorporated into the Tu-136 Zvezda manned hypersonic aircraft concept. [1]

The MARCAS (Manoeuvring Reentry Control and Ablation Studies) project was one of three technology demonstrator missions of the United States Air Force, with the primary goal to gather flight data on the aerodynamic and thermal effect of cross-flow jets that are used for hypersonic manoeuvrability. The program was part of the ABRES directorate and ran concurrently with the other two technology demonstrators that launched in 1966: MBRV and BGRV. The main contractor for the program was Douglass Aircraft, which was responsible for the vehicle design. [136]

These vehicles had a diameter of 0.33 m and were 1.52 m long. Instead of relying on aerodynamic surfaces, the MARCAS capsules made use of jet thrusters to change the vehicle’s flight direction. This allowed for reaction speeds ten times faster than aerodynamic surfaces and for manoeuvrability at higher altitudes, where the atmosphere is more tenuous. [136]

The first MARCAS flight occurred in October 1965, the second in January 1966, and the final one in May 1967. Both the first and second MARCAS flights were successful. The data from the third flight showed that the reaction jets caused no significant erosion on the surrounding material. It was found that reaction jets were less effective for attitude control at high altitudes. [136, 137]

Eventually, future manoeuvring hypersonic reentry vehicles, such as AMaRV, would primarily rely on aerodynamic surfaces for attitude control and flight path adjustments.  

A total of four MBRVs were flown, all launched by Atlas rockets from Vandenberg Airforce Base to an altitude of 1300 km, towards the Kwajalein atoll, where the large radar stations could track the vehicle. During the MBRV project, a new type of heat shield material, carbon-carbon composites, was developed for the Mark-12 reentry vehicle. The first two MBRV vehicles were equipped with the same material to collect flight data. In order to analyse the heat shield samples, a two-stage recovery system was installed, including a ballute drogue, three main parachutes, and a floatation bag. The last two MBRV flights had a radar payload onboard instead of the recovery system. [136]

In 1953, a series of recovery system drop tests were performed by high-altitude deployment from a B-52 aircraft at Point Mugu Naval Station. MBRV flew for the first time in August 1966. During the sustainer burn of the Atlas rocket, the vehicle veered too much off course, causing a necessary flight termination by range safety. The flight of the second MBRV happened in March 1967, when the vehicle successfully performed a 20g pull-up manoeuvre. Unfortunately, the recovery system failed, causing the loss of the last MBRV flight carrying the experimental heat shield for the Mark-12 reentry vehicle. The third MBRV flight was a success in July 1967: the vehicle performed a 25g manoeuvre and the telemetry payload successfully established a two-way transmission through the reentry plasma. During the fourth and final flight of MBRV in October 1967, an attempt was made to perform a pull-down dive manoeuvre. The vehicle successfully performed the manoeuvre with 80g acceleration at hypersonic speeds, by which fulfilled its mission goals. [136]

The BGRV project was one of several hypersonic manoeuvring technology demonstrators in the early ‘60s, funded by the United States Air Force, under the ABRES directorate (Advanced Ballistic Reentry Systems). The vehicle design was contracted to the McDonnell Aircraft Company. Its development and testing program was concurrent with that of the MBRV program. The objective was to demonstrate the capability of a boost-glide reentry trajectory for military target strikes. The reentry vehicles were launched with Atlas rockets from Vandenberg Airforce Base towards Wake Island in the Pacific Ocean. [136]

From the mid to late ‘60s, three manoeuvring reentry vehicle demonstrators were developed: MBRV, BGRV, and MARCAS. After they had proven that it is feasible to manoeuvre a vehicle at hypersonic speeds, there were still some technical difficulties that had to be overcome before a fully operational manoeuvring missile could become a reality. Therefore, two advanced manoeuvring demonstrator missions were initiated by the ABRES (Advanced Ballistic Reentry Systems) directorate of the United States Air Force. The first was called the Advanced Control Experiment (ACE), whose goal was to decrease the size and weight of the control mechanism and new inertial guidance system. For previous missions, these systems were found to be excessively large and heavy. [136]

The ACE vehicles had a length of 2.08 m, a diameter of 0.56 m, and were roughly 500 kg heavy. They were conical in shape, with a half angle of 10.4°. Prior to reentry, a set of small thrusters would be used for attitude control, similar to what had been done for previous manoeuvring reentry vehicles. Upon descending in the atmosphere, the actuated fins at the vehicle’s base provided the necessary force to steer the vehicle at accelerations up to 100 g’s. [136]

Eventually, three ACE vehicles were launched atop an Atlas rocket to an altitude of roughly 1400 km. Similar to most manoeuvring reentry vehicles, they were launched from Vandenberg over the Pacific Ocean towards the Kwajalein atoll, where the necessary tracking infrastructure was present. The first launch happened on the 30th of September in 1973. The vehicle manoeuvred successfully during reentry, however, a faulty prediction of atmospheric data caused it to break up at a low altitude. The second flight, on the 23rd of March 1974, was a complete success. The last vehicle flew on September 8 in 1974 and suffered from an anomaly at the booster interface. [136]

The ACE program matured the technologies necessary for an operational manoeuvring reentry vehicle onboard an ICBM in the United States, which would lead to the development of the Pershing-II missile.

The accuracy of such a vehicle is less than that of an actively controlled steering mechanism, however, the complexity, size and weight are reduced significantly. [137] The reduced accuracy was an acceptable loss compared to the advantages, especially when considering the limited space available in a submarine.

Five flight tests were conducted between 1975 and 1976, after which one more test flight in 1977 was conducted onboard the trident missile to prove its compatibility. Because of the Anti-Ballistic Missile Treaty in 1972, further development of the vehicle and technology was halted. [137]

Note: sometimes this reentry vehicle is referred to as the Mark 5 reentry vehicle, but not to be confused with the USAF’s Minuteman Mark 5 reentry vehicle from 1961.

The first AMaRV flight was conducted on the 20th of December 1979. An anomaly occurred during booster separation, making the vehicle unstable during its reentry. Even though the vehicle’s control mechanism worked, it failed to perform the intended diving manoeuvre and the vehicle only returned to a stable configuration too late in the flight. The second flight was on the 8th of October 1980 and the third and final AMaRV flight was performed on the 4th of October 1981. [136]

After these flights, the program was considered a success, as it had proven the capability of high-speed manoeuvrability during reentry.

Prior to the flights of SWERVE, the vehicle’s aerodynamic characteristics were studied extensively by using scale models in hypersonic wind tunnels. Some of the primary goals were to correlate the vehicle’s pitch with the flap deflection and to study where on the vehicle the boundary layer transitions from laminar to turbulent at different flight conditions and angles of attack. [165]

A total of three SWERVE vehicles were launched onboard Strypi-IX rockets from the Kauai island in the Hawaiian archipelago. The vehicles were launched in a sub-orbital trajectory towards the Johnston island. When diving at 12 times the speed of sound, the vehicle performed a pull-out manoeuvre, after which it entered a glide phase at Mach 8. The SWERVEs were equipped with photodiodes and more than 100 thermocouples to measure the temperature distribution across the vehicle, which allowed the engineers to determine where the boundary layer transitioned from laminar to turbulent. [165][166]

The SWERVE program provided Sandia National Laboratories with a valuable set of flight data that was used to validate the then novel and state-of-the-art computational fluid dynamics programs, together with the wind tunnel data. Additionally, it also matured the winged reentry technology and thereby lay the foundation for later winged reentry vehicles such as the AHW and even a proposal for a manned version of SWERVE: the Space Cruiser. 

The TDMaRV program was initiated to demonstrate the technology readiness of manoeuvring re-entry vehicles for their capability to penetrate and evade anti-ballistic missile defence systems. Although not the first program to demonstrate this capability, it was possibly a demonstration of the state-of-the-art evasion and penetration capabilities of the time. [167]

Not much is known about the project or vehicle except for the fact that a flight of TDMaRV occurred on the 18^th of January 1988 onboard a Minuteman-I rocket from Vandenberg Air Force Base, reaching an apogee of roughly 1300 km. As for nearly all manoeuvring re-entry vehicles, it flew towards the Kwajalein Atoll in the Pacific Ocean, where an extensive amount of tracking equipment was available. [168]