Steltzner: Mars Curiosity's Fabeled SkyCrane was a "Manuever," Not a "Thing"

Adam Steltzner, who headed the Entry, Descent and Landing (EDL) team for the Mars Science Laboratory (MSL) and its rover, Curiosity, corrected a widespread misperception about the mission’s SkyCrane during a lecture at the National Academy of Sciences last week.  It is not a “thing,” but a “maneuver,” he explained as he recounted the challenges of designing an EDL system for such a heavy lander and the lessons learned from the experience.

Steltzner was selected as the winner of the first Yvonne C. Brill Lectureship in Aerospace Engineering sponsored by the National Academy of Engineering and the American Institute of Aeronautics and Astronautics (AIAA).   This inaugural Brill Lecture was held on September 30, 2014.  A video of the event, which also includes tributes to Brill, a distinguished aerospace engineer who passed away last year, is available on the University of Maryland’s website.

Steltzner, an aerospace engineer at the Jet Propulsion Laboratory (JPL) in Pasadena, CA, provided a lot of detail of the design and testing of the EDL system for the 900 kilogram (2,000 pound) rover that recently completed its second Earth year (first Mars year) exploring the Red Planet.  The process of getting from the top of the Mars atmosphere to the surface was nicknamed early on as the Seven Minutes of Terror with an animation (narrated by Steltzner and colleagues) vividly showing just how much had to go right for the rover to safely settle at the bottom of Mars’ Gale Crater.

The term SkyCrane seemed to accurately describe the rocket-propelled device slowly lowering the rover, hanging from tethers, to the surface before it flies away out of sight to avoid landing on top of its precious cargo.  That is not the SkyCrane however.  It “is a maneuver, not a thing,” Steltzner emphasized, which was originally called “direct placement” before someone came up with the catchier nomenclature.  It is the “act” of lowering the rover to the surface and then flying away rather than the hardware employed to accomplish that feat.  He added that the SkyCrane was judged to be the “least unacceptable solution” to the question of how to land the heavy rover.

Steltzner shared lessons learned and some of the cost-saving measures JPL used such as basing the descent engine on the type used for the 1970s-era Viking Mars probes instead of starting from scratch.   As luck would have it, JPL’s Carl Guernsey had kept one of the Viking engines under his desk for all those years and it was used for testing for the MSL project.   NASA has landed other rovers on Mars since Viking, but they were much smaller and could use simpler landing technologies (e.g. airbags).

The lecture is full of entertaining engineering stories, such as how the first signal JPL received of the spacecraft’s condition as it “kissed” the Martian atmosphere on the way down was that it had entered at a bad angle with “catastrophic” results.  Steltzner and his team held their breaths until more signals arrived moments later showing a nominal entry into the atmosphere.  They later determined the error message was the result of a bad sensor.

The Brill Lectureship is a biennial award administered by AIAA, which will release a call for nominations for the next award at the appropriate time.

The September 30 event included several tributes to Brill from colleagues, family and friends.   Steve Battel, who served on the National Research Council’s Space Studies Board with Brill, offered highlights of Brill’s 60-year engineering career, including her invention of a hydrazine thruster when she worked for RCA (once one of the major U.S. satellite manufacturers) that revolutionized station-keeping for geostationary satellites and is still used today.  She received many honors for that invention, including the 2010 National Medal of Technology and Innovation presented by President Obama in 2011. 

Colleague Jill Tietjen recalled Brill’s role as mentor to many women engineers and determination to ensure that women were recognized for their achievements.   Brill’s son, Matt, charmingly described growing up with parents who inspired their two sons and daughter to become scientists or engineers themselves.  All did, though Matt revealed that his brother, Joe, originally an electrical engineer, decided to get an MBA and go into the financial services business after a Mars mission he worked on (Mars Observer) failed just before it was to enter Mars orbit in 1993.  The engineering tradition is now moving into a third generation — Matt’s daughter is studying engineering in college now.  Yvonne Brill was 88 when she died in March 2013.  She and her husband, Bill, a chemist, were married for 59 years until Bill’s death in 2010.

The creation of the Lectureship and organization of the September 30 event was led by Elaine Oran, a close friend of Brill’s who spent most of her career at the Naval Research Laboratory and recently moved to the University of Maryland, and is herself the winner of many awards.