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.
LOFTID may sound
like just an amusing trick, but the $93 million 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 tonnes — about the bulk of a small car.
اضافة اعلان
That is inadequate
for the larger landers, carrying 20 tonnes or more, that are needed for people
and the supplies they will need to survive on the red planet.
The device could be
described as a saucer, six meters wide when inflated. It is made of layers of
fabric that can survive falling into the atmosphere at 28,968kph and
temperatures close to 1,650 degrees Celsius.
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 four feet wide and 1 1/2 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 nine meters 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 lift-off 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 re-entry into the atmosphere.
Over the next few
minutes, compressed nitrogen gas inflated LOFTID’s heat shield, a set of nested
doughnut-shape tubes that looked 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 lift-off, the LOFTID device was bobbing in the Pacific Ocean about 800km
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.
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.”
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 re-entry, 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.”
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