Purpose of the flight and payload description
GPHAR stands for Guided Parafoil High Altitude Research. The primary objectives of the GPHAR program are to both investigate the flight envelope and mature the technology related to the deployment and flight of parafoils at altitudes above 25,000 ft. MSL. Development of this technology will enable capabilities such as recovery of scientific balloon payloads, recovery and re-use of rocket components, satellite recovery, ISS sample return, and Mars or other terrestrial body descent and landing systems. The program was carried out by Airborne Systems North America with support for this flight of Near Space Corporation through NASA's Flight Opportuities program.
The program had 3 primary technical challenges: 1) successful deployment and inflation of the parafoil system, 2) achieving a stable steady state flight condition, and 3) demonstrating stable and predictable response to Airborne Guidance Unit (AGU) control input. Given the lack of precedence of parafoil flight in low density atmosphere, achievement of any one of the three challenges would have been determined a success.
For the test Airborne Systems selected a sliderless static line deployment from an altitude of 50,000 to 60,000 ft. MSL, which for the provided balloon, was 224 lb. of lifted mass. To support this, an existing 230 ft2 personnel parafoil was custom modified and a low temperature low-pressure capable AGU system was designed and built. AGU software was designed to command a series of 4 programmed strokes vs.time that would essentially repeat in a loop during the estimated flight of 40 minutes. This design of repetitive controlled inputs would show trends in steady flight, turn, and stability performance over a wide range in altitude.
In the picture at left can be seen the flight train in the prelaunch configuration. The drop configuration included multiple redundant radio communications systems between the balloon, payload, AGU, and the mission control station at the launch site as well as an airborne and a ground-based recovery team. Two payload-mounted GoPro cameras were used to capture test video. The AGU included a thermostatically controlled battery heating system. The planned flight profile required wind conditions that preclude the possibility of the system from landing in populated areas, or over-flying at low altitude. Mission planning and profile simulations were performed jointly by AS and NSC leading up to the test event to ensure that the wind conditions were acceptable for the execution of a safe flight test. On the side of the gondola was located the Flight Termination System (FTS).
Details of the balloon flight
Balloon launched on: 6/6/2014
Launch site: Naval Air Station Tillamook, Oregon, US
Balloon launched by: Near Space Corporation (NSC)
Balloon manufacturer/size/composition: Zero Pressure Balloon
Flight identification number: SBS-02
End of flight (L for landing time, W for last contact, otherwise termination time): 6/6/2014
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 52 m
Landing site: Near Beaver, Oregon, US
Payload weight: 101.6 kg
On June 6, 2014, the first flight test (SBS-02) was successfully launched to an altitude of 57,122 ft (17.4 km) from Tillamook, Oregon and realized the first program objective: demonstration of low density/high velocity deployment and performance of a guided ram-air parachute at altitudes beyond the current state of the art. Some lessons learned:
Overall, the ram air canopy deployment was very clean and orderly and canopy flight performance was quite close to prior experience. These observations confirm that parafoil parachutes maintain flight and glide performance throughout the altitude envelope experienced.
This test provided crucial information about an unknown phenomenon concerning parafoil canopies that have high sensitivity to very small stroke inputs above 40,000 ft. This phenomenon can be expected for a wing loading of approximately 1:1, as tested. Data was collected showing very small strokes are capable of diving turns.
Concerning navigation and control, the test provided critical data that suggests, while the nature of the maneuvering dynamics are consistent with low altitude flight, the recovery time from a maneuver is longer at high altitude