Aeroshell
An aeroshell is a rigid
Its purpose is used during the EDL, or
Aeroshells are a key component of space probes that must land intact on the surface of any object with an
Components
The aeroshell consists of two main components: the
Design factors
A spacecraft's mission objective determines what flight requirements are needed to ensure mission success. These flight requirements are
The overall dynamics of aeroshells are influenced by inertial and drag forces, as defined it this equation: ß=m/CdA where m is defined as the mass of the aeroshell and its respective loads and CdA is defined as the amount of drag force an aeroshell can generate during a freestream condition. Overall, β is defined as mass divided by drag force (mas per unit drag area).[10] A higher mass per unit drag area causes aeroshell entry, descent, and landing to happen at low and dense points of the atmosphere and also reduces the elevation capability and the timeline margin for landing. This is because a higher mass/drag area means the spacecraft does not have sufficient drag to slow down early in its decent, relying on the thicker atmosphere found at lower altitudes for the majority of its deceleration.[1] Furthermore, higher mass/drag ratios mean less mass can be allocated to the spacecraft's payload which will have secondary impacts on funding and mission's science goals.[10] Factors that increase during EDL include heat load and rate, which causes the system to forcefully accommodate the increase in thermal loads.[11] This situation reduces the useful landed mass capability of entry, descent, and landing because an increase in thermal load leads to a heavier support structure and thermal protection system (TPS) of the aeroshell. Static stability also needs to be taken into consideration as it is necessary to maintain a high-drag altitude. This is why a swept aeroshell forebody as opposed to a blunt one is required; the previous shape ensures this factor's existence but also reduces drag area. Thus, there is a resulting tradeoff between drag and stability that affects the design of an aeroshell's shape. Lift-to-drag ratio is also another factor that needs to be considered. The ideal level for a lift-to-drag ration is at non-zero. Maintaining a non-zero L/D ratio allows for a higher parachute deployment altitude and reduced loads during deceleration.[12][10]
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 (49,000 m) 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.[13] 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.
The vehicle is being developed and tested by NASA's Jet Propulsion Laboratory.[14] Mark Adler is the project manager.[15]
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).[15] A high-altitude helium balloon, which when fully inflated has a volume of 1,120,000 cubic meters (39,570,000 cu ft),[14] lifted the vehicle to around 37,000 meters (120,000 ft).[16] The vehicle detached at 21:05 UTC (11:05 local),[15] and four small, solid-fuel rocket motors spun up the vehicle to provide stability.[16]
A half second after spin-up, the vehicle's
Upon slowing to Mach 2.5 (around 107 seconds after SIAD deployment
2015 test flights
Two more test flights of LDSD took place in mid-2015 at the Pacific Missile Range Facility. They focused on the 8-meter (26 ft) SIAD-E and SSDS technologies, incorporating lessons learned during the 2014 test.[20] Changes planned for the parachute include a rounder shape and structural reinforcement.[19] Shortly after re-entry, however, the parachute was torn away.[21]
Gallery
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Artist impression of theViking Orbiter releasing the aeroshell-clad lander (Don Davis).
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Mars Science Laboratory giant heat shield.
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Detail ofVirginia Air and Space Museum.
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33.5-meter Supersonic Ring Sail Parachute
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6-meter SIAD-R
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8-meter SIAD-E
References
- ^ a b Theisinger, John.E (2009). Multi-Objective Hypersonic Entry Aeroshell Shape Optimization. RESTON: AMER INST AERONAUT ASTRONAUT. p. 1.
- U.S. Department of Transportation. Archived from the original(PDF) on 19 March 2015. Retrieved 12 April 2015.
- ^ mars.nasa.gov. "Mars 2020's Aeroshell". NASA Mars Exploration. Retrieved 2022-11-16.
- ^ "Pioneer Venus Project Information". nssdc.gsfc.nasa.gov. Retrieved 2022-11-16.
- ^ Theisinger, John.E (2009). Multi-Objective Hypersonic Entry Aeroshell Shape Optimization. RESTON: AMER INST AERONAUT ASTRONAUT. p. 959.
- ^ a b "Aeroshells: Keeping Spacecraft Safe". Lockheed Martin. Retrieved 2019-12-02.
- ^ "Mars Exploration Rover Mission: The Mission". mars.nasa.gov. Retrieved 2019-12-02.
- ^ Smith, Douglas.H. Roller Coasters, G Forces, and Brain Trauma: On the Wrong Track?. Larchmont, NY: Mary Ann Liebert, Inc. pp. 1117–1118.
- ^ Kraft, Rachel (2021-04-08). "Orion Spacecraft to Test New Entry Technique on Artemis I Mission". NASA. Retrieved 2022-11-17.
- ^ a b c Theisinger, John.E (2009). Multi-Objective Hypersonic Entry Aeroshell Shape Optimization. RESTON: AMER INST AERONAUT ASTRONAUT. p. 958.
- ^ Returning from Space: Re-entry. Federal Aviation Administration - Advanced Aerospace Medicine On-line. pp. 310–311.
- ^ "Hypersonic Entry Aeroshell Shape Optimization" (PDF). Solar System Exploration. NASA. Archived from the original (PDF) on 27 April 2015. Retrieved 12 April 2015.
- CNN.com. Retrieved August 12, 2014.
- ^ a b c d "Press Kit: Low-Density Supersonic Decelerator (LDSD)" (PDF). NASA.gov. May 2014. Retrieved August 12, 2014.
- ^ a b c d Carney, Emily (July 1, 2014). "NASA's Low-Density Supersonic Decelerator Test Flight Hailed as a Success". AmericaSpace. Retrieved August 12, 2014.
- ^ a b c d e Parslow, Matthew (June 28, 2014). "LDSD passes primary technology test but suffers chute failure". NASA Spaceflight. Retrieved August 12, 2014.
- ^ a b c 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.
- ^ a b Boyle, Alan (August 8, 2014). "Flying Saucer Videos Reveal What Worked and What Didn't". NBC News. Retrieved August 12, 2014.
- ^ a b c Rosen, Julia (June 30, 2014). "NASA Mars test a success. Now to master the parachute". Los Angeles Times. Retrieved August 12, 2014.
- ^ Allman, Tim (June 9, 2015). "Parachute on Nasa 'flying saucer' fails in test". BBC. Retrieved June 9, 2015.
- "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
- Axdahl, Erik; Cruz, Juan R.; Schoenenberger, Mark; Wilhite, Alan. "Flight Dynamics of an Aeroshell Using an Attached Inflatable Aerodynamic Decelerator" (PDF). NASA.gov. American Institute of Aeronautics and Astronautics. Retrieved 12 April 2015.