An artist's impression shows LOFTID, which is designed to survive falling into the atmosphere at more than 28,968kmh and temperatures close to 1649C. Photo / Nasa via The New York Times
On Thursday morning, Nasa sent a giant inflatable device to space and then brought it back down from orbit, splashing in the ocean near Hawaii.
You might think of it as a bouncy castle from space, although the people in charge of the mission would prefer you did not.
“I would say that would be inaccurate,” Neil Cheatwood, principal investigator for the Low-Earth Orbit Flight Test of an Inflatable Decelerator, or LOFTID, said of the comparison during an interview.
LOFTID may sound like just an amusing trick, but the US$93 million (NZ$154.4m) project demonstrates an intriguing technology that could help Nasa in its goal of getting people safely to the surface of Mars someday. The agency has landed a series of robotic spacecraft on Mars, but the current approaches only work for payloads weighing up to about 1.5 tons — about the bulk of a small car.
That is inadequate for the larger landers, carrying 20 tons or more, that are needed for people and the supplies they will need to survive on the red planet.
A more accurate description of the device might be that it is a saucer, 20 feet (6m) wide when inflated. It is made of layers of fabric that can survive falling into the atmosphere at 18,000mph (28,968kmh) and temperatures close to 3000 degrees Fahrenheit (1649C).
Still, an inflatable heat shield shares a key characteristic with a bouncy castle: uninflated, it can be folded and packed tightly. LOFTID fit in a cylinder a bit over 4 feet wide and 1.5 feet high. For a traditional rigid heat shield, there is no way to cram something 20 feet in diameter into a rocket that is not that wide.
A larger surface such as LOFTID’s generates much more air friction — essentially it is a better brake as it slices through the upper atmosphere, and the greater drag allows heavier payloads to be slowed down. For future Mars missions, the inflatable heat shield would be combined with other systems such as parachutes and retrorockets to guide the lander en route to a soft landing.
That would require a heat shield about 30 feet in diameter, Cheatwood said, “because it’s such a high mass we’re trying to take to Mars for humans”.
On Thursday, the LOFTID team did not have much to do during the countdown to liftoff at 1.49am Pacific time aboard an Atlas V rocket. To avoid the possibility of causing problems with the main mission — the deployment of a weather satellite — the LOFTID systems were not turned on until an hour later, after the satellite was released.
The satellite, Joint Polar Satellite System-2 and now renamed NOAA-21 upon reaching orbit, will measure energy emanating from the planet through the atmosphere to improve weather forecasts.
After the weather satellite was deployed in orbit, the second stage of the rocket, with LOFTID still attached, briefly fired its engine twice to get LOFTID oriented properly for reentry into the atmosphere.
Over the next few minutes, compressed nitrogen gas inflated LOFTID’s heat shield, a set of nested doughnut-shaped tubes that look like a mushroom or a parasol popping out of the top of the rocket stage. To add stability to LOFTID, the rocket stage began spinning like a top at a languid three revolutions per minute before releasing the test craft for its journey through the atmosphere.
A couple of hours after liftoff, the LOFTID device was bobbing in the Pacific Ocean about 500 miles from Hawaii. Grainy infrared video taken from a recovery ship showed LOFTID descending under a parachute and then splashing in the water.
“Everybody’s just relieved and excited,” Greg Swanson, instrumentation lead for LOFTID, said during the Nasa Television broadcast. He was on the recovery ship on the way to the vehicle to pull it out of the water.
#LOFTID SPLASHDOWN! 💦🪂 pic.twitter.com/I4IwSzopMI
— ULA (@ulalaunch) November 10, 2022
The idea of inflatable heat shields goes back a half-century, but there were no materials that possessed the needed strength and heat resistance.
Cheatwood said that two decades ago, Steve Hughes, one of the lead engineers for LOFTID, read some papers describing Russian efforts on inflatable heat shields. “I thought that 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 a decade ago. Those 10-foot-wide inflatable shields were launched on suborbital rockets, essentially going straight up and then falling down. The LOFTID test doubles the diameter, and because the vehicle reached orbit, the reentry was much faster, generating more heat.
The success means that the technology is now ready to use on missions, Cheatwood said.
In addition to Mars, inflatable heat shields could aid landings on other worlds with atmospheres such as Venus and Titan, the largest moon of Saturn.
Closer to home, about a dozen companies have expressed interest in the technology, Cheatwood said. “And that’s not me going out and selling it to them,” he said. “That’s them contacting me.”
One is United Launch Alliance, the maker of the Atlas V rocket that launched LOFTID.
Spurred by the success of SpaceX, which regularly lands the booster stages of its Falcon 9 rockets, United Launch Alliance, a joint venture of Boeing and Lockheed Martin, wants to eventually reuse parts of Vulcan, its next-generation rocket, which is expected to fly for the first time next year.
Unlike SpaceX, the company is not looking to land the entire first stage.
Instead, the compartment at the back of the Vulcan booster containing the most expensive pieces — the engines — would be jettisoned and then fall 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 of catching rocket parts in midair.)
A small startup named Outpost Space is looking to create a novel space business that could use inflatable heat shield technology. In recent years, a slew of new rocket companies has driven down the cost of launching satellites to orbit. But getting anything back to Earth — such as drug samples or novel materials produced in the near-weightless environment of low-Earth orbit — remains limited and tricky. For now, that can be done only with payloads taken to the International Space Station or possibly China’s new space station.
Outpost, however, thinks that many researchers and companies would be happy to avoid trips to and from a space station, opting for much shorter trips to orbit.
Dunn said Outpost was aiming to launch the first orbital demonstration of its system next year.
“It’s basically a small platform that allows the payload to operate and to be exposed to the space environment,” Outpost CEO Jason Dunn said. “And then it returns. So it’s almost like a very small space station that just happens to come back after your mission.”
The Outpost team came upon the Nasa inflatable heat shields and has signed a contract for Nasa to develop versions it can use. Once the inflatable heat shield has shepherded Outpost’s spacecraft through the heat of reentry, a second inflatable system — a paraglider — deploys, and the payload can be guided precisely toward a landing spot.
The potential customers for Outpost “can’t either afford the space station round or they need to get it up and down faster,” Dunn said. “What we’ve been able to develop is a system that can fly really short missions that we can get in space and back in a month.”
This article originally appeared in The New York Times.
Written by: Kenneth Chang
Photographs by: Nasa via The New York Times
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