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NASA: Mars entry test a success despite chute snag
Posted: June 28, 2014

A giant helium balloon lifted a 3.5-ton flying saucer-shaped research vehicle to an altitude of more than 23 miles Saturday and released it for a dramatic rocket-powered boost through the extreme upper atmosphere to test an inflatable doughnut-like braking system and a huge supersonic parachute needed for future missions to Mars.

Artist's concept of the Low-Density Supersonic Decelerator. Credit: NASA
The inflatable aero-brake appeared to work normally in live video downlinked from the test vehicle, but the parachute, the largest ever built for deployment at more than twice the speed of sound, failed to fully inflate in a disappointment for flight controllers with NASA's Jet Propulsion Laboratory.

"PI (principal investigator) has called 'no chute.' We don't have full chute inflation," a flight controller reported.

The Low-Density Supersonic Decelerator then fell toward impact in the Pacific Ocean northwest of Hawaii. The carrier balloon apparently came apart after the LDSD's release and it was not immediately clear what recovery crews standing by in the landing zone might be able to retrieve.

In any case, the test flight appeared to meet all of its major objectives but one and engineers are hopeful recorded telemetry will shed light on what went wrong with the parachute deploy.

"Our objectives for this first flight are to launch it from here, get the balloon off and out over the water, to get it up to altitude where we can drop the vehicle and conduct this powered flight and get the data back from it to see how it works," Mark Adler, LDSD project manager at JPL, said before launch.

He stressed the test flight was just that, a test flight, and any number of things could go wrong. But "if we fire that motor and we get data back from it, that is a great day. That way we can learn exactly what happened and understand what to do for our next flights."

The idea was to put the Low-Density Supersonic Decelerator in the thin extreme upper atmosphere, at a velocity of more than four times the speed of sound, to mimic the conditions a Mars-bound spacecraft might experience slamming into the atmosphere of Mars.

The goal is to develop new atmospheric braking systems that will allow NASA to launch larger, more sophisticated landers to the red planet.

The heaviest spacecraft ever sent to the surface of Mars -- NASA's Mars Science Laboratory, or Curiosity rover -- tipped the scales at about one ton. To get heavier robots to the surface, and eventual crewed spacecraft that could weigh 20 tons or more, NASA must develop better systems to quickly slow large vehicles in the thin martian atmosphere.

Enter the Low-Density Supersonic Decelerator, or LDSD, the first of three test vehicles to fly in a $200 million research program aimed at developing new technologies for future Mars missions.

"Landing on Mars is an extremely challenging thing to do," Ian Clark, principal investigator at the Jet Propulsion Laboratory in Pasadena, Calif., said during a preflight briefing. "The atmosphere is extremely thin, it's about 1 percent the density of Earth's atmosphere. That means you need very large devices to react against the atmosphere to create the drag that we use to slow the vehicles down as they enter the atmosphere.

"If you want to land things that are even heavier than the Mars Science Laboratory, if you want to land several tons -- and as you cast your eyes to the horizon and you think about landing humans on the surface of Mars, missions that will be 10 to 15 tons, 20 tons or more -- you're going to need extremely large drag devices to slow those vehicles down. We don't have those currently, and that's what LDSD is developing."

The Low-Density Supersonic Decelerator includes a saucer-shaped decelerator and a new supersonic parachute. Credit: NASA
The test vehicle's high-altitude balloon, filled with 34 million cubic feet of helium, lifted off from the U.S. Navy's Pacific Missile Range Facility on Kauai, Hawaii, at 2:40 p.m. EDT (GMT-4). Initial attempts to launch the craft earlier this month were blocked by the weather, but conditions were acceptable Saturday and the balloon was cleared for flight.

A live television feed showed the giant balloon climbing away, pulling the LDSD from its support cradle and up into the sky for a two-hour 25-minute climb to an altitude of around 120,000 feet above the Pacific Ocean west of the test range.

After a series of final readiness checks, commands were sent to release the LDSD from the balloon. As it briefly fell back toward Earth, small rocket motors fired to spin the vehicle up for stability before an ATK Star 48 solid-fuel rocket motor ignited to accelerate the test article and boost it an additional 11 miles to some 180,000 feet, or 34 miles.

The test vehicle featured two new technologies. The first was an inflatable torus around a traditional heat shield known as the Supersonic Inflatable Aerodynamic Decelerator, or SIAD, that gives the test vehicle the general shape of a flying saucer. The second new technology was a huge parachute, the largest ever designed to deploy at more than twice the speed of sound.

Flying at more than four times the speed of sound, the flight plan called for the heavily instrumented SIAD torus to inflate, expanding the diameter of the entry vehicle from about 15.4 feet to 19.7 feet. After slowing to about 2.5 times the speed of sound, the parachute was expected to deploy.

All of that appeared to go like clockwork.

"All spin motors fired," someone said as the LDSD fell from the carrier balloon. Seconds later, the Star 48 rocket motor ignited.

"Mach 1," a flight controller called, monitoring telemetry as the vehicle accelerated through the speed of sound. Seconds later, "Mach 2."

"Acceleration is good, vehicle is stable," a controller said.

As the spacecraft passed through Mach 3, telemetry showed "acceleration is good, vehicle is stable." Live video showed a torrent of fiery exhaust blasting from the nozzle of the Star 48 as the limb of the Earth wheeled about in the background.

A few seconds later, the test vehicle was moving at more than four times the speed of sound. The rocket motor then burned out and small motors fired to stop the vehicle's stabilizing spin.

Go-Pro video cameras capatured the inflation of the SIAD, followed by the parachute's release. Live video showed the huge chute streaming behind the test vehicle, but it never inflated to its full 110-foot diameter.

"Come on..." someone said anxiously.

The supersonic parachute on NASA's Low-Density Supersonic Decelerator deployed from the saucer-shaped test vehicle, but it never fully inflated. Credit: NASA TV/Spaceflight Now
But it was not to be. A few moments later, the a flight controller called "PI (principle investigator) has called 'no chute.' We don't have full chute inflation."

"I'm going to declare that a bad chute, is that your understanding?" the flight director asked.

"That's affirm."

"Please inform the recovery director we have bad chute."

The SIAD torus initially was tested at the Naval Air Weapons Station at China Lake, Calif., using a rocket sled to accelerate the device to several hundred miles per hour. To test the parachute, a long cable was connected, fed through a pulley system and attached to a rocket sled. The parachute then was released from a helicopter, the rocket sled was fired up and the parachute was pulled toward the ground with a force equivalent to about 100,000 pounds of drag.

But to fully test the system engineers wanted to duplicate conditions a spacecraft would experience at Mars.

"What we're trying to do is replicate the environment in which these technologies would be used," Clark said before flight. "That means replicating the atmosphere, in particular the density of the atmosphere, which at Mars is extremely thin. To find (those conditions) we have to go halfway to the edge of space, or about 180,000 feet here on Earth, to test these devices. And we have to go several times the speed of sound."

Two more LDSD vehicles are being built for "flights of record" next summer.

"We've been there before, eight successful landings on the surface of Mars, the United States leads in this area," said Mike Gazarik, director of space technology development at NASA Headquarters. "It's one of the more difficult challenges.

"When we look at the Curiosity rover, which landed two years ago, it's about a metric ton on the surface of Mars. We know that for exploration, for future robotic exploration, for future human exploration, we need more than that. ... And so for us, it's the challenges of Mars -- how do we get there, how do we land there, how do we live there, how do we leave there?"

The Low-Density Supersonic Decelerator "focuses on that very difficult challenge of landing there."

"We need to test and we need to learn," Gazarik said. "And we need to do it quickly and efficiently. ... It's about more mass, going to more elevations on the surface of Mars and landing more accurately."