On Thursday morning, NASA sent a giant inflatable device into space and then brought it back from orbit, splashing into the ocean off Hawaii.
You could think of it as a bouncy castle from space, although the people in charge of the mission wish you didn’t.
“I’d say that would be inaccurate,” Neil Cheatwood, principal investigator of the Low-Earth Orbit Flight Test of an Inflatable Decelerator, or LOFTID for short, said of the comparison during an interview.
LOFTID may sound like a funny trick, but the $93 million project showcases an intriguing technology that could help NASA achieve its goal of one day bringing humans safely to the surface of Mars. The agency has landed a series of robotic spacecraft on Mars, but current approaches only work for payloads weighing up to about 1.5 tons — about the bulk of a small car.
That’s not enough for the larger landers, carrying 20 tons or more, needed for the people and supplies they need to survive on the red planet.
A more accurate description of the device might be that it is a saucer, 20 feet wide when inflated. It’s made of layers of dust that can survive falling into the atmosphere at speeds of 18,000 miles per hour and temperatures close to 3,000 degrees Fahrenheit.
Still, an inflatable heat shield shares an important feature with a bouncy castle: When uninflated, it can be folded and packed tightly. LOFTID fit into a cylinder just over 1.20 meters wide and 1.5 meters high. For a traditional rigid heat shield, there’s no way to cram something 20 feet in diameter into a rocket that isn’t that wide.
A larger surface area like that of LOFTIDs generates a lot more air friction – essentially it’s a better brake as it cuts through the upper atmosphere, and the greater drag allows heavier loads to be slowed down. For future Mars missions, the inflatable heat shield would be combined with other systems such as parachutes and retro rockets to guide the lander on its way to a soft landing.
That would require a heat shield about 30 feet in diameter, said Dr. Cheatwood, “because it’s such a high mass that we’re trying to bring humans to Mars.”
On Thursday, the LOFTID team had little to do during the countdown to 1:49 a.m. Pacific time launch aboard an Atlas V rocket. To prevent problems with the main mission – deploying a weather satellite – the LOFTID systems were not activated until an hour later, after the satellite had been released.
The satellite, Joint Polar Satellite System-2 and now renamed NOAA-21 upon reaching orbit, will measure the energy coming from the planet through the atmosphere to improve weather forecasts.
After the weather satellite entered orbit, the rocket’s second stage, with the LOFTID still attached, fired twice briefly at the motor to orient the LOFTID correctly for reentry.
Over the next few minutes, compressed nitrogen gas blew up LOFTID’s heat shield, a set of nested donut-shaped tubes that looked like a mushroom or parasol emerging from the top of the rocket stage. To add stability to LOFTID, the rocket stage started spinning like a spinning top at a languid three revolutions per minute before releasing the test craft for its journey through the atmosphere.
A few hours after launch, the LOFTID device bobbed in the Pacific Ocean, about 500 miles from Hawaii. Grainy infrared video taken from a salvage ship showed LOFTID descending under a parachute and then splashing into the water.
“Everyone is just relieved and excited,” Greg Swanson, the instrumentation leader for LOFTID, said on the NASA Television broadcast. He was on the salvage ship heading for the vehicle to retrieve it from the water.
The idea of inflatable heat shields goes back half a century, but there were no materials that had the necessary strength and heat resistance.
dr. Cheatwood said Steve Hughes, one of LOFTID’s chief engineers, read some articles 20 years ago describing Russia’s efforts on inflatable heat shields. “I thought it was a good idea,” he said. “Between the two of us, we were kind of the ones pulling it together.”
That led to three tests ten years ago. Those 10-foot-wide inflatable shields were launched on suborbital rockets, which essentially went straight up and then plummeted down. The LOFTID test doubles the diameter, and because the vehicle reached the track, the return was much faster, generating more heat.
The success means the technology is now ready for use on missions, said Dr. cheatwood.
In addition to Mars, inflatable heat shields could also aid landings on other worlds with atmospheres such as Venus and Titan, Saturn’s largest moon.
Closer to home, about a dozen companies have expressed interest in the technology, said Dr. cheatwood. “And that’s not me going out and selling it to them,” he said. “Those are the ones who contact me.”
One is United Launch Alliance, maker of the Atlas V rocket that launched LOFTID.
Spurred on by the success of SpaceX, which regularly lands the booster stages of its Falcon 9 rockets, United Launch Alliance, a joint venture between Boeing and Lockheed Martin, aims to eventually reuse parts of Vulcan, its next-generation rocket, which is expected to launch next year. flying for the first time.
Unlike SpaceX, the company doesn’t plan to land the entire first stage.
Instead, the compartment in the back of the Vulcan booster containing the most expensive parts – the engines – would be jettisoned and then fell back to Earth, slowed first by an inflatable heat shield and then parachutes. A helicopter would then catch the descending engine compartment and take it to a ship. (Another rocket company, Rocket Lab, is trying a similar approach to trapping rocket parts in mid-air.)
A small start-up called Outpost Space wants to set up a new space company that can use inflatable heat shield technology. In recent years, a slew of new rocket companies have cut the cost of launching satellites into orbit. But getting anything back to Earth — such as drug samples or new materials produced in the near-weightless environment of low-Earth orbit — remains limited and tricky. For now, that can only be done with payloads brought to the International Space Station or possibly to China’s new space station.
However, Outpost thinks many researchers and companies would like to avoid traveling to and from a space station and opt for much shorter trips to orbit.
Mr Dunn said Outpost aims to launch the first orbital demonstration of its system next year.
“It’s basically a small platform that allows the payload to operate and be exposed to the space environment,” said Jason Dunn, the company’s CEO. “And then it comes back. So it’s almost like a very small space station that just happens to come back after your mission.”
The Outpost team stumbled upon NASA’s inflatable heat shields and signed a contract with NASA to develop versions it can use. Once the inflatable heat shield has guided the Outpost spacecraft through the heat of reentry, a second inflatable system – a paraglider – is deployed and the payload can be precisely guided to a landing site.
Outpost’s potential customers “can’t afford the space station or they have to get it up and down faster,” said Mr. Dunn. “What we’ve been able to develop is a system that can fly very short missions that we can get into space and back within a month.”