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Curiosity rover assembled as cost impacts debated

Posted: August 5, 2009

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Assembly and test of the Mars Science Laboratory rover, and its Sky Crane descent stage, are accelerating at the Jet Propulsion Laboratory in Pasadena, Calif. toward launch on an Atlas 5 from Cape Canaveral in October or November 2011.

Cutting edge technology for MSL is springing to life as the flight rover and descent stage mature in JPL clean rooms.

The MSL rover, the size of an Earthly wide-track all terrain vehicle, will be lowered on a bridal from the highly maneuverable Sky Crane Mars Descent Stage. The descent stage will be hovered at 50 ft. altitude on its 8 rocket engines until the rover wheels are on the ground and the umbilical severed. (See Descent System image below).

Credit: NASA
The Sky Crane contraption looks like its out of a Star Trek movie. Once free of the rover it will zoom off at low level and full throttle until it runs out of fuel and crashes far from planned roving targets.

Developing such cutting edge hardware has brought technology delays and a much steeper price than envisioned. The MSL cost growth is also slowing the development of all other NASA planetary programs and will delay by 2-4 years all other Mars programs coming after MSL, including a Mars sample return now envisioned for the 2020s.

The cost and hardware problems also forced an MSL launch slip from 2009 to 2011. And it also caused a management shakeup in the organization.

Richard Cook who initially led the program has been moved down to deputy manager, while Pete Theisinger has been convinced to return to lead the MSL program He earlier led the Spirit and Opportunity programs.

At this point two years before launch, the MSL program is also preparing two major cost updates for top NASA management and Congress about MSL cost overruns and development difficulties.

This is occurring at the same time NASA and the European Space Agency have joined forces for Mars planning focused on Europe's plan to launch its own ExoMars rover (pictured below).

Credit: ESA
ExoMars was originally scheduled to lift off for Mars on an Ariane 5 in 2011, but its launch has now been postponed a total of 7 years to 2018.

The first MSL review is due this summer and called a "breach report" that will cite to Congress how the program has "breached" its earlier funding plan. MSL is burdened with a $1.68 billion (68%) development overrun and prospects for the need of an additional $115 million to finish the program.

An even more critical review will be the flight's "readiness to proceed" review set for November where JPL and the space agency will update progress toward solving major actuator, avionics and power system problems being tackled this summer.

The power system situation is relatively new. To solve the problem with the actuators, the program went to a different lubricant. But the new lubricant requires more heating during cold Martian nights, a situation that uses up the capability of the RTG with decaying Plutonium 238. The RTG will be mounted on the back of the rover between the large fin like structures visible in this image of the flight rover.

Credit: NASA
The rover is equipped with its flight-sized wheels enabling the large scale of the vehicle to be seen.

The rover's Sample Analysis (SAM) handling equipment being developed at the Goddard Space Flight Center has also fallen behind. But testing indicates "almost double energy requirements" will be needed to conduct SAM sample analysis scenarios.

According to a mid July NASA Advisory Council Report the "Rover Power System design does not meet present mission requirements, requiring the rover to need additional battery capacity and possibly addition of a solar array in addition to its nuclear power system.

The electrical issue could be a significant new cost driver as the solar array/nuclear system tradeoff was one of the most important design tradeoffs when the program got started. Now the assessment has changed to raise the possibility that MSL may need both a solar array and nuclear generator.

The maturity of the rover and Sky Crane design at JPL is illustrated by examining the engineering detail of the Sky Crane, as the 4,565 lb. carrier is viewed from above with the rover tucked into its "bomb bay" below.

Credit: NASA
All of the red boxed areas are delicate red rocket nozzles mounted on four arms to provide descent thrust after separation of a 50 ft. parachute and aeroshell. With twin rocked engines firing on all four corners, the vehicle can maneuver to a precise location throttle down into a hover at 50 ft. (15 meter) altitude then lower the rover to the ground.

To lower the rover, an umbilical line will be unraveled from the gold cone shaped device mounted in the center of the Sky Crane's belly. The component (shown below) is essential for mission success.

Credit: NASA
JPL has also begun separation tests of the rover from the Sky Crane. Such tests are being done manually in a JPL clean room where the rover, still minus its science instruments is mated to the Sky Crane descent stage.

The locks holding the lander onto the Sky Crane are released freeing the rover for separation. The release is simulated on the ground by having technicians pull the Sky Crane upward manually with ropes, rather than have the rover fall from the flyer in the clean room. More advanced outdoor test rigs will perform higher fidelity tests.

The missions cruise stage, aeroshell, heat shield and parachute are other critical elements of the mission being integrated at JPL.

The cruise stage (shown below) functions like the same systems used on the 1997 Pathfinder mission and the ones attached to Spirit and Opportunity.

Credit: NASA
The large circular structure (above) sits atop the aero shell and has rocket engines and propellant to carry out course corrections enroute to Mars. It is separated just before atmospheric entry.

When the cruise stage is mounted atop the aeroshell, it forms the shelter that carries the rover and Sky Crane on the 200 million mi. flight to Mars and the dive through the Martian atmosphere.

Credit: NASA
The aeroshell is much larger for MSL than it was for Spirit and Opportunity and Pathfinder.

The most critical component of the aeroshell is the 15 ft. diameter Lockheed heat shield that faces into the aerodynamic flow during atmospheric entry . (See picture below)

Credit: NASA
The Mars Science Laboratory heat shield has a curved lenticular shape to allow the guidance system to achieve lift to maneuver in cross range by rotating the shell during entry. This closed loop guidance capability will give MSL a much more accurate landing ability.

Once the fiery dive through the atmosphere is completed, MSl will deploy its 51 ft. dia. parachute developed by Pioneer Aerospace in South Windsor , Conn. For MSL the chute is 10 ft. wider than those use on the Spirit and Opportunity missions.

Credit: NASA
The 3,000 sq. ft. chute with a lower open ring section at bottom is designed to fly at Mach 2.2 in the Martian atmosphere. It is shown during a recent wind tunnel test at the NASA Ames Research Center, Mountain w, Calif. Note technician for scale in the image (above).