Parachute Test Missions

The American space program got a kick-start from using the V-2 rockets taken after World War II. These rockets and the V-2 rockets build by the US after the war were tested at the white sands testing ground [67]. Part of the launches at the White Sands testing ground was under project Blossom. Project Blossom was a project to measure and test various parameters in flight and deploy a canister that was recovered through a parachute system. Onboard of the five flights that were flown on four rhesus monkeys were placed, and on the last flight, a mouse was placed all with medical equipment to check how animals would behave when it would become weightless [65].

The canister would be ejected from the tip of the V-2 where previously the warhead would be located. For the first flight, the canister had a size of 0.56 m^3. In subsequent flights, the canister was increased to 2.27-2.83 m^3 after the first flight by extending the nosecone[65,66]. The canister was limited in weight for all five flights to 907 kg. The canister was recovered using a two-stage parachute system. First, at apogee, a 2.44 m diameter ribbon parachute was deployed to limit the speed of the canister as it descended. After 165 seconds after deployment of the drogue, the 14ft main ribbon parachute is deployed [65,67].

None of the five flights was successfully recovered. The third flight failed because of the launcher exploding. All the other four flights had a successful flight and separation, but none were successful when it came to the recovery part of the flight [64,65].

A mission flown in the sixties by NASA that still provides data for parachutes today is the PEPP or the Planetary Entry Parachute Program. Two vehicles were used for this program: a rocket vehicle and a balloon/rocket vehicle. For the second vehicle, a  balloon was released. When the balloon reached the highest point, a rocket engine was fired. This rocket engine ensured the test subject reached the desired Mach number, where the balloon ensured a dynamic pressure comparable to that of Mars. The mission tested cross parachutes, disk gap band parachutes, Ringsail parachutes, and Ballutes to test these designs for Mars missions, primarily the Viking landers.

The unique mission architecture meant that the missions were quite expensive but necessary. Due to the high cost, these type of complicated missions has not been re-flown since. This resulted in pretty much every Mars mission relying, in part, on the PEPP results. Some later flights were performed under the Supersonic Planetary Entry Decelerator program or SPED. These objectives were, however quite similar to those of PEPP.

Note notable example was a single parachute flight test under the SPED-II program. With the exception of a single PEPP flight, all tests were done with slender forebodies. SPED-II tested the parachute using a blunt body, more like a Mars lander [19]. 

The Supersonic High-Altitude Parachute Experiment (SHAPE) was the successor of the PEPP and had very similar goals: testing parachutes at high altitudes and high velocities. SHAPE pushed the envelope of the parachutes by going higher and faster than PEPP, up to Mach 3 and 60 km altitude. Therefore, all test articles had to be launched with a three-stage rocket, an Honest John-Nike-Nike configuration, similar to some of the PEPP missions.

Three 12.2-meter diameter parachutes were tested during the SHAPE program: a disc-gap-band and ringsail type parachute. These tests provided NASA with more knowledge and understanding of the behaviour of these parachutes in high velocity, low density environments. [3,4]

The Balloon Launched Decelerator Test (BLDT) program had the objective to flight qualify the 16.1-meter diameter disk-gap-band (DGB) parachute for the first US Mars lander, called Viking. The parachute was qualified by flight testing it behind the turbulent wake of the BLDT vehicle at conditions representative to a Martian mission. The choice of using a DGB for the Viking Mars mission was based on the results of the PEPP program in the mid-'60s, where DGB, ringsail, ballute and cross parachutes were tested at supersonic conditions [74][75].

A total of four different test flights (AV-1 to AV-4) took place at the White Sands missile base (US) during the summer of 1972: one subsonic drop test, a transonic flight and two supersonic flights. The vehicle is a blunt cone with a 140° angle and a diameter of 3.5 meters. The flight profile of the super- and transonic flights was very similar to that of the balloon launched PEPP flights. A large high-altitude balloon would carry the test vehicle up to about 37 km high. Then, after the balloon was released, a set of solid rocket motors ignited and boosted the vehicle higher up in the atmosphere and up to the supersonic conditions. During the ascent phase, the parachute is deployed by a mortar. After the release of the aerodynamic shell, the test vehicle and parachute land, followed by the retrieval operations. [74][75]

Flight AV-1 of the BLDT program encountered a large rip in the parachute’s dacron canopy. On the video footage, it was clear that the initial failure occurred during the deployment of the parachute from its bag. A high amount of friction between the bag and parachute during deployment was identified as the cause of the initial canopy damage. A large amount of friction was a consequence of a large angle of attack (13°) and excessive dynamic pressure at deployment, which caused an asymmetrical inflation of the parachute from its bag. Regardless of the canopy damage, the parachute managed to perform within the acceptable range of a similar Mars mission [76].

SuperMax was a mission flown onboard the Maxus-9 sounding rocket, the last of the giant European Maxus sounding rockets. The mission was launched with the objective of testing a disk gap band parachute at supersonic velocities for the planned ExoMars rover. The SUPERMAX test vehicle was the first piggy-back payload flown aboard a sounding rocket with the aim of performing a flight test of a supersonic parachute. The system was built by Vorticity and was flown by SSC with the support of ESA.  A test flight was conducted instead of wind tunnel testing due to the high cost of supersonic wind tunnels. As the flight was done onboard a sounding rocket, there was limited space, and thus the capsule was quite small. The parachute was only 1.25 meters in diameter and flew 3.045 meters behind the capsule. The small capsule was only 13.8 kg and placed in the space between the rocket motor and the rest of the experiments and was released when the two separated. SuperMax reached an apogee of 713 km and a max heat load of 1.3 MW/m2. The capsule was aerodynamically stable and oriented itself in a heat shield down position automatically. 

During the fight, the parachute inflated at Mach 1.7 and dynamic pressure of 11.5 kPa. These conditions lead to an inflation load of 12 kN on the vehicle. The entire inflation lasted for only 0.014 seconds. The experiment showed that the inflation loads of the disk gap band at supersonic conditions were much higher than expected. The parachute triggering was done using a timer system that deployed the capsule at a certain moment after separation. 

A parachute test mission not flown by an aerospace agency, but by a student team is the Supersonic Parachute Experiment Aboard REXUS (SPEAR). The mission has been created and is operated by Delft Aerospace Rocket Engineering, known for their Stratos sounding rocket family. The mission is set to fly onboard REXUS 28, part of the REXUS/BEXUS program organised by SNSA, DLR, ESA, SSC, and ZARM. The mission is centred around the same drogue parachute flown onboard Stratos III and Stratos IV and was set to fly in March 2020 in Sweden. The drogue parachute, a 0.2 m2 Hemisflo ribbon parachute made out of aramid, is identical to the drogue parachute flown onboard Stratos III and will fly onboard Stratos IV. The mission uses a cluster of two Disk-Gap-Band main parachutes for a safe landing. An interesting fact is that the capsule is not stable and requires a stabilising drag cone to be deployed during atmospheric re-entry. The mission was postponed due to the COVID-19 pandemic.

The Low-density Supersonic Decelerator was a flight testing an inflatable heat shield and a new type of parachute. The capsule consisted of a 6 and 8-meter SIAD or Supersonic Inflatable Aerodynamic Decelerator. The capsule was lifted using a high altitude balloon where the vehicle would be spun up, a Star 48 solid rocket motor would accelerate the vehicle to almost Mach 5 and the vehicle would spin down. Then the heat shield was inflated and the vehicle would decelerate. After some time a mortar system fired a ballute pilot chute which would pull out a 100-foot (30.5m) disk sail parachute. The ballute was chosen as the central location of LDSD was taken up by the Star 48 motor and firing a 100-foot parachute from an off-set mortar was a risk to the vehicle. The SIAD worked as expected but during both flights, the main parachute ruptured. After the first flight, a research committee was set up to analyse the incident. They performed several rocket sled tests to validate the performance at high dynamic pressure, but at subsonic velocities. With confidence, the second mission was launched, but the parachute ruptured again. These flights showed a lack of understanding in supersonic parachute inflation which lead to the ASPIRE program. 

The mission quite resembles the NASA ASPIRE missions and served a similar purpose. Several sources do indicate that the flight was repeated four times validating the supersonic performance of the main parachute. [98]

The parachute was tested using a rocket-boosted vehicle at a low altitude, with deployment occurring around 3000 m above mean sea level. The deployment velocity was approximately 1000 m/s. The parachute was deployed using a mortar with an ejection velocity greater than 20 m/s. The parachute's conical ribbon design was chosen for its high drag and good performance under these extreme conditions. It was constructed from FONLON, a material similar to Kevlar-29, known for its resistance to aerodynamic heating and high tensile strength.

Key features of the parachute included its geometric porosity, the use of anti-overinflation lines made of nylon to limit initial inflation load, and the absence of a reefing system. The nylon overinflation line melted at Mach 3, but served its purpose. The tests demonstrated the parachute's durability and effectiveness, with minor damage observed but no structural failures, validating its design for high-speed, high-pressure environments.

The CARE mission was part of India’s crewed capsule development program. In contrast to its predecessor, SRE (Space capsule Recovery Experiment), the CARE capsule resembles the shape of the Gaganyaan capsule in which one day three Indian astronauts will fly to space. The goal of the mission was to demonstrate ISRO’s capabilities of a safe re-entry and recovery of future crewed missions to space and to validate the Gaganyaan parachute recovery system in flight.

The capsule was launched on top of the GSLV-III launch vehicle from the Satish Dhawan launch complex on a sub-orbital trajectory. After re-entry, the apex cover was ejected, followed by the deployment of two pilot chutes. These on their turn deployed the drogue chutes that slowed down the capsule to 50 m/s. At 5 km altitude, two main parachutes are deployed to guarantee a safe splashdown into the Bay of Bengal. Each parachute stage consists of two identical chutes for redundancy to allow for a safe landing in case of a parachute failure.

The flight was a success and marked a great step for India’s development of its crewed space program. Other missions such as the SRE vehicles and pad abort tests have, together with CARE, contributed greatly towards the technology readiness of Gaganyaan. [60,61]