NASA favors propulsive Mars landings over supersonic parachutes

by Chris Bergin

NASA’s Human Architecture Team (HAT) has opted to remove supersonic parachutes as an option for landing “human-scale hardware” on the surface of Mars. The decision will result in all forward planning involving a mix of supersonic retro propulsion in combination with deployable, inflatable, and rigid aeroshells for missions to the Red Planet.

Landing On Mars: 

NASA is the global leader in successfully landing spacecraft on the surface of the Red Planet.

Each success has enabled NASA to advance its understanding of not only Mars itself, but the challenges of safely placing a spacecraft on to the Martian terrain.

NASA’s heritage reaches as far back as the two Viking landers arrived on the Red Planet in 1976. However, it’s the Mars Exploration Rovers (MER) that have blazed a trail for Martian science.

The precursor for MER was the Pathfinder Rover, the first spacecraft to land on Mars since the Viking success.

Utilizing an atmospheric entry aeroshell capsule that was derived from the original Viking Mars lander design, a supersonic parachute, solid rocket motors and large airbags to cushion the impact, were employed to safely land the rover.

Arriving in the Ares Vallis region of Mars, the Sojourner Rover enjoyed working on Mars for five times longer than was originally expected.

The success led to an ambitious attempt to land two larger rovers on the surface, MER-A Spirit and MER-B Opportunity.

2015-04-08-162744Once again, the lessons of Viking and Pathfinder were employed with the aeroshell, followed by an up-scaling of the the Pathfinder landing systems, such as the parachute – which was 40 percent larger for MER – and the airbags that resulted in the rovers bouncing on the surface of Mars before finally coming to rest.

Both Rovers landed successfully, before going on to once again exceed expectations with their missions of the surface of Mars.

The latest mission to land on Mars was the Curiosity rover. However, due to the size of the Rover, a radical change to the Entry, Descent and Landing (EDL) techniques was required.

To accomplish such a feat, Mars Science Laboratory engineers designed a new high-precision EDL system that included a propulsive descent.

This consisted of six different spacecraft configurations, 76 pyrotechnic devices, the largest supersonic parachute ever designed and manufactured, and more than 500,000 lines of code to execute the required maneuvers to safely ease Curiosity on to the surface via the Skycrane method.

The success was one of NASA’s greatest achievements, as the confirmation was relayed to the team at the Jet Propulsion Laboratory (JPL) that the rover was wheels down on the surface of Mars.

2014-09-02 11_05_50-www.nasa.gov_sites_default_files_files_Green_Joint_PSD_HEO_TAGGED.pdfOnce again, the experience gained from the successful EDL has allowed for the sister vehicle (the 2020 Rover) to further refine the key events of a Martian landing.

Curiosity’s dive towards the surface show the 2020 Rover can enjoy the allowance of a lighter Thermal Protection System (TPS), along with refinements that could allow for an even greater “precision” landing on the Red Planet.

At least another 10 years will pass before NASA realizes its ambition of humans landing on Mars, with the current plan pointing to a notional target of sometime in the 2030s.

However, the work of the Rovers is feeding into the ongoing evaluations into how to land both humans and assets on the planet.

2015-04-08-162911Launching the hardware will be via the Space Launch System (SLS), landing the hardware on Mars remains notional, with graphical representations continuing to point to somewhat out-dated overviews, such as the Design Reference Architecture (DRA) 5.0 reference material.

That overview shows a mix of aeroshell, parachute and propulsive techniques to allow huge landers to deploy on the surface.

Concept Of Operations (CONOPS) documentation also pointed to the use of a Supersonic Parachute system aiding the descent – albeit for a very short period. However, NASA’s Human Architecture Team (HAT) have now opted to refine the approach that plays more into the recent EDL advances.

2015-04-08-171043“The Human Architecture Team (HAT) presented the Mars Entry, Descent and Landing (EDL) pathfinder study plan to the STMD Program Management Council (DPMC). The study plan was approved, which will lead to a near-term decision on the most promising technology approach for human-scale Mars EDL solutions,” noted L2 information.

“The HAT held a supersonic parachute workshop in which the consensus was that supersonic parachutes are not applicable to landing human scale payloads (>10 metric tons) on Mars.

“As a result, further entry, descent, and landing studies will only consider concepts for supersonic retro propulsion in combination with deployable, inflatable, and rigid aeroshells.”

2014-06-28 18_43_29-LDSD Press Kit.pdfWhile the use of propulsive technology has an embedded history in both NASA’s previous EDL techniques – and has become a major drive in SpaceX’s plans both for Earth and Mars related missions – the highlighting of the aeroshell technology points to the recent testing of NASA’s Low-Density Supersonic Decelerator (LDSD) project.

LDSD is gathering the required data about landing heavy payloads on Mars and other planetary surfaces, utilizing a Supersonic Inflatable Aerodynamic Decelerator (SIAD).

2014-06-28 18_44_47-NASA's _flying saucer__ The Low Density Supersonic Decelerator (LDSD)The concept involves increasing the size of the aeroshell, creating a much larger surface area, generating more drag in the very thin Martian atmosphere.

The first test of the LDSD technology occurred in June 2014, at the US Navy’s Pacific Missile Range Facility (PMRF) on Kauai, Hawaii.

The test was a success, despite a failure of the Supersonic Disk Sail Parachute during deployment, hardware the LDSD technology may now be involved in eventually replacing during actual missions to land on Mars.

A second test is expected to take place in June.

A question remains for how NASA envisions the touchdown scenario for Mars landers, with the potential of using subsonic chutes in tandem with propulsive landing, or to opt for a fully propulsive touchdown.

(Images: via L2, NASA and SpaceX)

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