The first (and smallest) torus for
the 10-meter aeroshell NASA is developing
with ULA, sitting on top of the six-meter
LOFTID aeroshell that completed its
mission in November 2022. Credit: NASA
Space agencies are advancing inflatable heat shields they see as not only key for future missions to Mars, but also for unlocking fully reusable rockets and larger cargo deliveries back to Earth.
Since the dawn of the space era, rigid aeroshells have been the mainstay for safely returning people and cargo through the atmosphere with the aid of parachutes and retro propulsion.
However, they are limited by the shape of launch vehicle fairings and can be no more than four to five meters based on what is currently available.
“That four to five meters limits the amount of down mass you can bring back from orbit,” Joe Del Corso, project manager for the Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) at NASA’s at Langley Research Center, said in an interview. “The bigger you can make the aeroshell during the re-entry phase, the more mass you can bring back from orbit.”
A four-to-five-meter rigid aeroshell using classic heat-resistant materials is suitable for returning up to one and a half metric tons from space.
Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology, on the other hand, can be compacted for launch, and then inflated to far larger sizes to protect spacecraft from burning up in the atmosphere.
A larger surface area increases drag, slowing down the spacecraft more effectively during re-entry, and this is particularly useful for a planet with a thin atmosphere such as Mars to ensure safe deceleration and landing.
“For us, we’re looking at going from one and a half metric tons to 20-40 metric tons,” Del Corso said.
LOFTID’s success paved the way for NASA to work with United Launch Alliance and other industry partners to develop larger,
more capable inflatable heat shields. Source: NASA
“One and a half metric tons is a well-instrumented golf cart. 20-40 metric tons is more like a small ranch house, fully furnished with a car in the carport.”
Inflatables are also generally lighter than rigids, leveraging flexible materials that enable them to conform to various shapes and sizes for a greater variety of payloads and missions.
But while traditional rigid heat shields like those used on SpaceX’s Dragon cargo transportation spacecraft are well-proven, it’s still early days for HIADs.
After launching on China’s Long March 5B rocket in 2020, an experimental Chinese cargo spacecraft with an inflatable, umbrella-shaped heat shield about three meters in diameter failed on its return to Earth.
Two years later, NASA’s LOFTID took off as a secondary payload on a United Launch Alliance Atlas 5 rocket, and successfully splashed down a six-meter HIAD — the largest blunt body aeroshell to ever go through atmospheric entry.
Europe enters the race
In June, Europe kicked off ICARUS, or Inflatable Concept Aeroshell for the Recovery of a re-Usable launcher Stage, which would culminate in 2028 with the return of a three-meter demonstrator after launching on a sounding rocket.
The European Commission recently awarded a consortium led by Deimos, the technology branch of Spanish contractor Elecnor, 10 million euros ($11 million) of funding for ICARUS.
Ali Gülhan, head of the department for supersonic and hypersonic technology at DLR, and principal investigator for ICARUS at the German space agency, said one of the main advantages of a foldable inflatable system is its compatibility with rockets and spacecraft already in use.
“Such inflatable aeroshells can be more easily integrated into existing launcher systems and used for heavy re-entry configurations,” Gülhan said.
DLR is responsible for the ICARUS launch campaign, flight test and the re-entry vehicle’s health monitoring system.
“In addition to several ground experiments to demonstrate or to verify the functionality of selected subsystems, a complete inflatable aeroshell payload will be tested in a ballistic flight with a two-stage sounding rocket configuration,” he said.
“The separation of the payload from the launcher and the deployment of the folded inflatable structure are critical events of the flight experiment.”
According to Deimos CEO Simone Centouri, the mission would set Europe up for testing a 10-meter shield that could help launchers bring back rockets for reuse, particularly for stages housing costly avionics and propulsion systems.
“If we have the possibility to reuse something [then] this is good because the impact of resources on Earth is lower,” Centouri continued, “and you can reduce your ecological footprint.”
NASA goes large
With a 1.1 metric ton re-entry mass, LOFTID withstood about 11.3 metric tons of drag load on the aeroshell during the November 2022 demo.
Since then, NASA has been “approached by a number of different companies and agencies looking to utilize the HIAD technology,” according to Del Corso.
United Launch Alliance has a Space Act Agreement with NASA to develop a larger inflatable heat shield for recovering BE-4 booster engines, which account for 65-70% of the cost of ULA’s next-generation Vulcan rocket.
NASA said the LOFTID test of an inflatable heat shield, seen here after recovery form the Pacific, was a success.
Credit:
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