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Emily LakdawallaNovember 13, 2008

Piecing together MSL

This is a neat animation posted to the Mars Science Laboratory (MSL) website today. It documents the first time that the descent stage was stacked onto the rover, or as much as the rover as has been assembled, anyway. Good news! The two fit together nicely.

MSL, meet your ride to Mars


MSL, meet your ride to Mars
On November 12, engineers at JPL stacked the body of the MSL rover to its descent stage for the first time. The descent stage is the component of the spacecraft that will use rockets and cables to slow MSL's descent toward the surface and then lower it to the ground before flying off to crash elsewhere. Fortunately, the two pieces were a good fit. They will be stacked and unstacked repeatedly as assembly and testing continues.
It's sort of difficult to see the shape of the rover just yet. The white box is the rover's body, which houses all the electronics and the sample analysis instruments. Or it will house those soon -- I don't believe any of the sample analysis instruments have been delivered to JPL yet. There are black rectangular boxes of various shapes stuck to the front and top of the body -- I am guessing those are mass models for the arm and its handful of instruments and the mast and its cameras. I see only two wheels, stuck to the back of the rover -- those must represent where the wheels are located while the rover is in launch and cruise. The wide-set "legs" of the rover must be folded up during launch and cruise, but I'm not totally sure how that works. In the last frame of the animation, we're looking at the backside of the rover, and you can see a frame jutting out the back end that will eventually hold the rover's radioisotope thermal generator (RTG).

I was privileged to have a tour of JPL not long ago and I saw the descent stage, cruise stage, and aeroshell, but not the rover, at a slightly earlier phase of construction. Here's a top-down view of the cruise stage, taken from behind glass in the viewing gallery:

MSL descent stage under construction

MSL descent stage under construction
There are four pairs of rockets, the red things inside the cages at the outside "corners" of the descent stage. They are huge. Three of the yellow-orange tanks are to contain propellant, and two are for pressurizing the propellant. The radar system that will guide MSL's approach to the surface will attach to the thingy on the front (bottom) of the cruise stage in this view. There's nothing sticking onto the back (top) of the cruise stage because that's where the RTG will be poking out. Inside the central triangle you can see a gold thingy, which is the bridle, the cable on which MSL will be lowered to the surface from the descent stage, in what JPLers have been referring to as the "skycrane maneuver." The bridle is wrapped around a conical spool, attached to a motor. It's offset from the center of the cruise stage because that's the direction that the center of gravity of the rover is offset, due to the heavy weight of the RTG.

Here's a different view, many shots from my camera assembled into a panorama of the whole "high bay" assembly facility:

MSL spacecraft components under construction

Emily Lakdawalla

MSL spacecraft components under construction
The rover itself was inside the black tent in the left rear corner, I think for some planetary protection-related work to make the rover very clean. On the left, in the foreground, is the descent stage. On the right in the foreground, underneath a scaffold, is the unbelievably enormous aeroshell, the "top" of the clamshell that will protect the descent stage and rover during launch and cruise. The "bottom" of the clamshell is the heat shield, which had not been delivered yet at the time I took these pictures.

It's difficult to convey how large that aeroshell is. For those of you who are familiar with the Apollo missions, this is larger than the Apollo aeroshell. There is a hatch in the front of the aeroshell that looks exactly the right size for an astronaut to crawl through, and little holes that look for all the world like portholes, just the right size for an astronaut to peep out. You can see one porthole to the right of the hatch in my photo -- there are portholes just like that all the way around the bottom edge of the aeroshell.

If it's not to tempt a stowaway, what's the hatch for? It's there so they can attach the RTG at the last possible moment, just a few days before launch. The thing throws off so much heat that it's actually in danger of overheating the spacecraft, so the cavernous assembly building they'll be using to do the final stacking of the spacecraft onto the rocket has three redundant air conditioning systems to work hard at keeping the thing cool until it's safely launched into cold space. The "portholes" are there for balancing purposes -- they're spots where they can adjust ballast during the final spin-balancing.

Getting back to the photo, in the middle ground on the right is an enormous armature that they had to custom-build in order to be able to turn over the stack of stuff mid-assembly. In the background on the right in the rear is the cruise stage, which is still a bit skeletal at this point. There are likely "interesting things" under the gray foil on tables in the background. I was told that one of them is probably DAN, the Russian instrument, one of two that had been delivered at the time that I visited; the other already-delivered instrument was MARDI, the descent camera, which, I was told, was probably already integrated onto the spacecraft.

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Emily Lakdawalla

Solar System Specialist for The Planetary Society
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