Safely delivering spacecraft to Earth & other celestial bodies
About Entry Systems
[image-51][image-67]Entry Systems are the complete package of heat shields, parachutes, software, and other articles needed for a vehicle to successfully transition from space to operations in the atmosphere of a planet or land on the planet's surface.
Because of the extreme heat of entering an atmosphere from space, the outside of a vehicle can reach temperatures of 7,000 degrees Fahrenheit. Even if the spacecraft survives this intense heat, it must then be able to "fly" at hyper velocity speeds and eventually slow down to land. All of this requires very specialized hardware.
Every NASA launched spacecraft that has entered another planet's atmosphere or landed on another planet as well as every NASA launched vehicle that has returned from space to land on Earth has been directly or indirectly enabled by the entry systems work at Ames.
The Ames Entry Systems & Technology Division has been a part of developing and testing every NASA human rated entry system to date. Iconic vehicles such as Apollo and the Space Shuttle, as well as the pioneering vehicles such as Mercury and Gemini, at the birth of our country's space age, have all been touched by Ames scientists. Ames' contributions continue today helping with the success of Mars Science Laboratory and into the future with plans for near asteroid missions.
Ames entry systems capabilities include:
Aerothermodynamics – provides integrated modeling, simulation and testing capabilities for aerothermodynamics, hypersonic and high enthalpy fluid dynamics, shock layer radiation, and aerodynamic configuration design.
Thermo-Physics Facilities – operates hyper-velocity ground testing facilities, each providing unique atmospheric high-speed flight conditions, essential for technology development and flight system validation.
Thermal Protection Materials – develops new and improves existing thermal protection materials. Ames Also develops methods and techniques for characterizing materials, as well as analyzing and designing models required to understand material behaviors to predict and guide thermal protection system development.
Entry System and Vehicle development – performs and coordinates system level integration for existing and future atmospheric entry vehicles. Ames' primary role is to apply technologies and capabilities to analyze, design, develop, test, evaluate, manufacture, certify and operate atmospheric entry vehicles and systems.
Ames also provides:
- Systems analysis, system engineering, aero/thermal database construction, and low speed aerodynamics analysis to couple with the development of next generation heat shield technologies.
- Fundamental modeling and simulation for exploring and understanding the underlying physics governing hypersonic flows required for computer code development to be used for the prediction of gas-phase radiation analysis.
- Engineering systems for developing the structural and mechanical designs for deployable aeroshells in collaboration with cutting edge transformable heat shield technologies.
- Supercomputing facilities to perform massively parallel calculations on thousands of CPU cores for structural response modeling and aeorothermal environments determination.
Featured example: Mars Science Laboratory
How did Ames help take the edge off of Curiosity's "seven minutes of terror"?
[image-83]NASA's Mars Science Laboratory (MSL) spacecraft with the Curiosity rover arrived at Mars on Aug. 5, 2012. Curiosity, carrying laboratory instruments to analyze samples of rocks, soil and atmosphere, is now investigating whether Mars has ever offered environmental conditions favorable for microbial life. The Entry Science Division at NASA Ames Research Center contributed to the successful MSL Entry Descent and Landing (EDL) success in several ways.
- PICA: Researchers invented the unique thermal protection system consisting of tiles made of Phenolic Impregnated Carbon Ablator (PICA) that the MSL spacecraft will use to safely reach the surface of the Red Planet.
- Arc Jet testing: The MSL heat shield was tested at Ames' Arc Jet Complex, which reproduces heating and pressure conditions similar to those experienced by spacecraft during atmospheric re-entry.
- MEDLI: The Mars Science Laboratory Entry, Descent, and Landing Instrument (MEDLI) contains multiple sophisticated temperature sensors to measure atmospheric conditions and performance of the capsule's heat shield.
Featured example: Hypersonic entry, descent and landing
What do you use to predict conditions of entering another planet's atmosphere?
[image-99]Radiative heating can be a significant portion of the total heat flow to a vehicle surface, particularly at high velocities or for large vehicles. Radiative heating is caused by an entry vehicle colliding with the molecules in the atmosphere. When these gasses become so energized that they begin to emit light (or, more specifically, electromagnetic radiation, because ultraviolet and infrared rays are also produced) the radiation is sufficiently intense to heat the vehicle.
In the shock tube, which measures radiative heating, a planetary gas mixture is accelerated to speeds of up to 50 times the speed of sound in order to simulate planetary (re)entry conditions. At these speeds the gas may reach temperatures of 20,000K (35,000F) and will radiate at similar magnitudes to real conditions. This radiation is measured using sensors tuned to pick up ultraviolet through the mid-infrared waves in a vacuu, giving data that is resolved as a function of position in the shock and wavelength (see image). This work is performed at Ames' Electric Arc Shock Tube (EAST), which is the only facility of its kind.
Predictions of radiative heating are performed by the NEQAIR (Non-equilibrium Air) code, a computer program which takes the composition and temperature of the gas to produce a simulated spectrum of the radiation produced. NEQAIR can predict radiative heating for all relevant atmospheres found in our solar system, including Earth, Mars, Venus, Titan and the gas giant planets. The NEQAIR code has been validated against a multitude of EAST facility experiments and generally compares favorably to the experimental results.
Featured example: Orion
Who do you call to design a new heat shield?
[image-115]In April of 2011 the baseline Orion heat shield design was canceled due to manufacturing risks associated with the remaining process and material development challenges. TS personnel were sent to Denver for extended TDY to work in-line tasks with Lockheed Martin (LM) to find a solution for the heat shield. In the first four months TS personnel and the LM Orion HS stress team completed a trade study on four heat shield architectures. Specific tasks involved a preliminary sizing of each design for use in mass and risk estimates, understanding the thermally induced loads into the system, and the implications to the thermal protection system.
In August 2011 the stress team supported the down select to the new heat shield carrier structure. The down select resulted in a classical skin stringer design with a solid carbon cyanate ester outer skin and titanium stringers. The team continued to work in Denver with LM focusing efforts on the new heat shield design. Tasks included stringer design trade studies, laminate springback predictions for the heat shield, material property test development, and the development and implementation of a methodology to size the stringers, laminate skin and fasteners. These tasks were in direct support of the LM drawing release in early 2012. The Orion heat shield is currently being assembled at Lockheed Martin and TS personnel continue to support ground handling operations, Q-notes, the heat shield proof test, and other various heat shield tasks.
Featured example: SpaceX Dragon
What NASA Ames materials and expertise were applied to SpaceX's Dragon capsule?
[image-131]The Entry Systems and Technology (TS) Division has a collaborative agreement with SpaceX under the commercial Orbital Transportation Services (COTS) program through a Reimbursable Space Act Agreement. It is funded by the COTS program as a means of privatizing space cargo and crew transportation. SpaceX's Dragon spacecraft has delivered cargo – and will later deliver crew – to the International Space Station. The TS Division's involvement with the development of SpaceX's Dragon spacecraft ranges from aerothermal simulation to thermal structural analysis. Using the award-winning DPLR tool developed within the TS Division, CFD simulations have predicted the trajectory and aerothermal heating expected for the Dragon capsule upon re-entry. With Dragon's entry conditions established, SpaceX has utilized the TS Division's arc-jet facilities for its thermal protection system design and testing.
The design and material properties of the heatshield for Dragon were heavily influenced by contributions from TS, with SpaceX developing and implementing its own PICA-X variant of the Division's patented PICA thermal protection material. The relationship between SpaceX and Ames has been mutually beneficial, and will continue for the foreseeable future.