Entry test missions

Not only the parachute systems require testing, but some missions are also launched just to validate the performance of a thermal protection system. An overview of these missions can be found here. 

The RLV-TD is a reusable demonstrator made and operated by ISRO. The subscale-winged demonstrator first flew in 2016 on top of a 9-ton HS9 solid rocket motor. This flight occurred on May the 23rd 2016. the rocket lifted off to about 65 km after which it performed a controlled entry and safe landing in the Bay of Bengal. The vehicle was not recovered from the ocean, and telemetry sent the data back. 

In 2023 the RLV-RD will continue testing in the landing experiment. During these experiments, the vehicle will be dropped from about 2.4 km, which it will fly back to a landing strip. 

After completing SHEFEX I and II, DLR used the information gathered during these projects for the next step. This step was to perform a test flight with a winged vehicle which should resemble a possible winged first stage of a reusable launch vehicle. This is the reusable flight experiment ReFEX. Its goals are to gain operational experience with winged first stages and, more generally, to gather flight and design data [142].

ReFEX is currently planned to be launched in 2024 in Australia. When it does and is separated from the VSB-30 rocket, it will start to descend. Part of the goal of gaining operational experience for winged stages is to test the autonomous GNC system and perform certain manoeuvres with the vehicle [142]. ReFEX will first make sure that it is belly-up when going into its hypersonic phase of the flight. This unusual orientation is due to stability reasons, as the tail fin would have no control when in the “normal” belly-down orientation [142]. Once ReFEX reaches Mach 1.5, it will rotate to a belly-down configuration, during which time it will also perform a turning manoeuvre. The end of the experiment is set at 8-10 km, after which ReFEX will perform a hard horizontal landing because it has neither a parachute nor landing gear for a soft landing.

IXV (Intermediate eXperimental Vehicle) was an intermediate step in the development programme for an autonomous European space transportation system. The programme started in 2002 as a follow-on of ARD (Atmospheric Reentry Demonstrator), a re-entry capsule that was launched atop an Ariane 5 in 1998 [149]. Rather than a blunt body type re-entry capsule like ARD, IXV was a lifting body type vehicle. This means that the shape of its fuselage generated lift without requiring wings, making it simpler than a winged vehicle like the Space Shuttle but more controllable than a blunt body re-entry vehicle like ARD or most crewed re-entry capsules. IXV performed a single suborbital test flight in 2015 on a Vega rocket and was the first lifting body to demonstrate re-entry under conditions representative of re-entry from Low Earth Orbit [149] [150]. The IXV programme has since been moved into the Space Rider programme, which aims to become Europe’s reusable space transportation system [150].

The ESA Atmospheric Reentry Demonstrator or ARD was flown in the interstage of the third Ariane 5 rocket. The objective was to demonstrate the ability of ESA to perform a controlled atmospheric re-entry. The capsule was a scale model of the Apollo-style capsule and flew to an apogee of 830km. During the flight, the heat shield reached a temperature of about 900 deg C. The capsule performed multiple manoeuvres during entry demonstrating the ability of ESA to safely return a capsule through the atmosphere. The capsule was equipped with a parachute system for a safe landing. The drogue parachute had a diameter of 5.8 meters. The drogue was followed by a cluster of three 22.9 meter diameter main parachutes. To ensure the capsule remained afloat two balloons were attached and inflated during landing. 

As no human-rated spacecraft had re-entered at speeds corresponding to those Apollo would encounter during its return from the Moon, NASA decided to investigate this re-entry and not rely on the current data available and extrapolate this to the required re-entry conditions [161,162]. This was named project FIRE (Flight Investigation Re-entry Environment). Its objective was to gather data on convective and radiative heating, radio attenuation and material behaviour during a re-entry similar to a return trajectory from the Moon [163,164].

To accomplish these velocities, without actually having to fly a spacecraft to the Moon and back, project FIRE would be launched on an Atlas-D into a ballistic trajectory. However, the power of the Atlas launcher would not be enough to reach the required velocity of 11.3 km/s during re-entry [163,164]. So to achieve the needed velocity, an Antares II solid rocket motor was to accompany the re-entry capsule to, right before re-entry, give the final boost.

After separation from the Antares II solid rocket motor, the 85 kg Project FIRE capsules would speed towards the ground at 11.3 km/s when at 12.2 km above the ground. To survive the re-entry, it had multiple alternating layers of phenolic-asbestos and beryllium as a  heatshield, which were embedded calorimeters to measure the heat rate. Besides this, small quartz windows were made in the heatshield to actually see into the flow. However, as it was known before the flight that because of the intensity of re-entry, the heat sensors and the quartz windows would not survive, multiple sensors were buried within multiple layers of the heatshield [163,164].

As the project FIRE capsules did not have a deceleration system, the data needed to be transmitted. This was done with a delay to make sure that the data would be sent in the window after the re-entry black-out and before splashdown in the Atlantic [163,164].

The European eXPerimental Re-Entry Testbed (EXPERT) is a hypersonic reentry vehicle designed by the European space agency. The goal of the mission is to address the scarcity of hypersonic flight data and to validate aero-thermodynamic models.

The vehicle was intended to be launched on a suborbital trajectory by a Russian submarine-launched Volna rocket. The launch was originally scheduled for mid-2012 however the Russian Ministry of Defence announced its desire to no longer provide the Volna rocket as a launch vehicle. Unable to find an alternative, low-cost launcher the EXPERT vehicle was placed into storage where it remains today.

The Phoenix capsule of SpaceWorks is a hypersonic test vehicle designed to act as a recoverable flight test bed for research in hypersonic regimes. The capsule will launch on a separate booster after which it will fly a ballistic trajectory and will land safely using a two-stage parachute system. This parachute system is stated to have a supersonic drogue parachute, although no details have been released. 

The capsule is a conical vehicle with a length of about 1.2 meters and a mass of 30 kg. The vehicle is currently in conceptual design with funding from the US Airforce AFWERX SBIR [160].