An aeroshell is a rigid heat-shielded shell that protects a vehicle from pressure and heat created by drag during atmospheric entry (see blunt body theory), slows it down during entry, and may protect it from debris during spaceflight. The back shell carries the load being delivered, along with important components such as a parachute, rocket engines, and monitoring electronics like an inertial measurement unit that monitors the orientation of the shell during parachute-slowed descent.
Aeroshells are a key component of space probes that must land intact on the surface of any object with an atmosphere. They have been used on all missions returning payloads to the Earth (if one counts the Space Shuttle thermal protection system as an aeroshell). They are also used for all landing missions to Mars, Venus, Titan and (in the most extreme case) the Galileo probe to Jupiter.
Planetary Entry Parachute Program
NASA's Planetary Entry Parachute Program (PEPP) aeroshell, tested in 1966, was created to test parachutes for the Voyager Mars landing program. To simulate the thin Martian atmosphere, the parachute needed to be used at an altitude more than 160,000 feet above the Earth. A balloon launched from Roswell, New Mexico was used to initially lift the aeroshell. The balloon then drifted west to the White Sands Missile Range, where the vehicle was dropped and the engines beneath the vehicle boosted it to the required altitude, where the parachute was deployed.
The Voyager program was later canceled, replaced by the much smaller Viking program several years later. NASA reused the Voyager name for the Voyager 1 and Voyager 2 probes to the outer planets, which had nothing to do with the Mars Voyager program.
Low-Density Supersonic Decelerator
The Low-Density Supersonic Decelerator or LDSD is a space vehicle designed to create atmospheric drag in order to decelerate during entry through a planet's atmosphere. It is essentially a disc-shaped vehicle containing an inflatable, doughnut-shaped balloon around the outside. The use of this type of system may allow an increase in the payload.
It is intended to be used to help a spacecraft decelerate before landing on Mars. This is done by inflating the balloon around the vehicle to increase the surface area and create atmospheric drag. After sufficient deceleration, a parachute on a long tether deploys to further slow the vehicle.
June 2014 test flight
The test flight took place on June 28, 2014, with the test vehicle launching from the United States Navy's Pacific Missile Range Facility in Kauaʻi, Hawaiʻi, at 18:45 UTC (08:45 local). A high-altitude helium balloon, which when fully inflated has a volume of 1,120,000 cubic meters (39,570,000 cu ft), lifted the vehicle to around 37,000 meters (120,000 ft). The vehicle detached at 21:05 UTC (11:05 local), and four small, solid-fuel rocket motors spun up the vehicle to provide stability.
A half second after spin-up, the vehicle's Star 48B solid-fuel motor ignited, powering the vehicle to Mach 4 and an altitude of approximately 55,000 meters (180,000 ft). Immediately after rocket burn-out, four more rocket motors despun the vehicle. Upon slowing to Mach 3.8, the 6-meter (20 ft) tube-shaped Supersonic Inflatable Aerodynamic Decelerator (SIAD-R configuration) deployed. SIAD is intended to increase atmospheric drag on the vehicle by increasing the surface area of its leading side, thus increasing the rate of deceleration.
Upon slowing to Mach 2.5 (around 107 seconds after SIAD deployment), the Supersonic Disk Sail (SSDS) parachute was deployed to slow the vehicle further. This parachute measures 33.5 meters (110 ft) in diameter, nearly twice as large as the one used for the Mars Science Laboratory mission. However, it began tearing apart after deployment, and the vehicle impacted the Pacific Ocean at 21:35 UTC (11:35 local) travelling 32 to 48 kilometers per hour (20 to 30 mph). All hardware and data recorders were recovered. Despite the parachute incident, the mission was declared a success; the primary goal was proving the flight worthiness of the test vehicle, while SIAD and SSDS were secondary experiments.
2015 test flights
Two more test flights of LDSD will take place in mid-2015 at the Pacific Missile Range Facility. These will focus on the 8-meter (26 ft) SIAD-E and SSDS technologies, incorporating lessons learned during the 2014 test. Changes planned for the parachute include a rounder shape and structural reinforcement.
Mars Science Laboratory giant heat shield.
- Erdman, Shelby Lin; Botelho, Greg (June 29, 2014). "NASA tests flying saucer craft for future manned mission to Mars". CNN.com. Retrieved August 12, 2014.
- "Press Kit: Low-Density Supersonic Decelerator (LDSD)". NASA.gov. May 2014. Retrieved August 12, 2014.
- Carney, Emily (July 1, 2014). "NASA's Low-Density Supersonic Decelerator Test Flight Hailed as a Success". AmericaSpace. Retrieved August 12, 2014.
- Parslow, Matthew (June 28, 2014). "LDSD passes primary technology test but suffers chute failure". NASA Spaceflight. Retrieved August 12, 2014.
- McKinnon, Mika (June 29, 2014). "A Successful First Flight for of the Saucer Test Vehicle over Hawaii". io9.com. Retrieved August 12, 2014.
- Chang, Alicia (June 1, 2014). "NASA to test giant Mars parachute on Earth". Las Vegas Review-Journal. Associated Press. Retrieved August 12, 2014.
- Boyle, Alan (August 8, 2014). "Flying Saucer Videos Reveal What Worked and What Didn't". NBC News. Retrieved August 12, 2014.
- Rosen, Julia (June 30, 2014). "NASA Mars test a success. Now to master the parachute". Los Angeles Times. Retrieved August 12, 2014.
- "Lockheed Martin To Design Mars Science Lab Aeroshell". Mars Daily. 2006-03-30. Retrieved 2007-02-17.
- "For Fuel Conservation in Space, NASA Engineers Prescribe Aerocapture". NASA. 2006-08-17. Retrieved 2007-02-17.
- Space travel guide
- Early Reentry Vehicles: Blunt Bodies and Ablatives