The rovers separated from their cruise stages about 15 minutes before atmospheric entry, they would have been doing 5.4 km/s at the point they slammed into the atmosphere. How much of the 193 kg of the cruise stage would have survived passage through the atmosphere, how fast would it have been going when it impacted the surface and has anyone identified the impact location or have an image of the crater. I'm posting this in the Oppy thread as we visited Oppy's 78 kg heatshield impact site but impact location calculations and imaging of Spirits cruise stage impact site would be most welcome.

The thought has crossed my mind - I'm not sure if any studies have been done. I imagine SOME of it would make it thru -fuel tanks in particular ( a delta II second stage tank can make it thru earth entry, after all ) - but I dont know if they'd be uprange or downrange.

Doug

Where the cruisestage might be, is an easy question, but probably very complex to find out (and answer). First, due to the extra drag (more friction with respect to the smooth and aerodynamically formed heatshield) in the initial stage of entry (before the parachute is released) i guess it should be uprange. Secondly, due to it's greater mass however, one could say that it's kinetic energy (1/2 *mass * velocity2) is able to "push" it further downrange (in other words: the cruisestage takes more time to slow down because of it's higher inertial momentum compared to the heatshield/MER capsule). Then, (thirdly), we must state that the cruisestage keeps on going at dazling speed, while the MER capsule is descending at an ever slowing pace due to it's parachute.

That was the "easy" part. The hard (fourth) part comes when you take into account in which direction the cruisestage is pushed at separation. I suppose it did not stay behind the MER capsule, because release of the parachute at a certain moment could be folowed by a head-tail collision because of the ever speeding (parachuteless) cruisestage. I guess the separation is deliberately performed in an a-symetrical way (which looks like it considering the Daniel Maas video), so that it is pushed slightly from the entrypath of MER. And a shift of only 5 degrees in orbit, can make it land.....(taking a 500 km atmospheric entry path as a rough assumption)...45 km apart of MER's landing spot.

Hope they simply find it in MGS (or MRO later on) images

This get's me to another questions for you people (which probably has to move to the MGS threads): Is hard- and software for analyzing MGS images (or other spacecraft imagery) capable of finding and detecting changes over time in the pictures (like Clyde Tombaugh found Pluto by comparing two timeframes) ? If this could be done automated, surely the chance of finding the cruisestages (or polar lander, or beagle II, or.....) would increase dramatically.

I have been looking for seperation sequencing commands which would give some clue as to the eventual relative motions of the cruise stage/lander. However I would imagine that seperation is performed symetrically then the cruise stage is deflected, probably by a lateral burn. The timing (coupled with relative spin rates) and duration of the burn would probably help refine the parameters of the impact site.

Hmm, if it broke up there maybe there will be no significant impact craters to observe. I would still like to see the equivalent of this

for the rest of the ship.

No - the cruise stage is totally dead once it's seperated, it cant do any sort of deflection burn.

It'll either be uprange a bit, or downrange a bit - depending on it's relative deceleration and profile thru the atmosphere compared to the nominal EDL sequence of the rest of the spacecraft.

Part of me thinks that it's fairly large and comparatively light - so it would slow down quite quickly - but then perhaps the fuel tanks would seperate from it and go further down-range. Frankly - I have no idea

Doug

The cruise stage, not being particularly aerodynamic, would have broken up into a lot of pieces at max deceleration. How far the individual pieces travel depends on their ratio of mass vs. drag.

The least massive pieces with the greatest surface area would have burned up, contributing a little metal to the global aerosol dust. Beyond a certain threshhold of this ratio (not necessarily the lightest or heaviest pieces, just beyond a certain point in the mass/drag ratio), a piece will survive max heating and reach the ground.

Since each piece has a different mass/drag ratio, and since that ratio changes dynamically as the air thickens, speed slows and material ablates, the pieces all separate and form a debris footprint. That footprint will almost always fall *short* of a protected entry body (like the heatshield-protected capsule) because, in the process of breaking up, the total mass of the unprotected body (in this case, the cruise stage) suddenly presents tens of times more surface area to the atmosphere it's ramming into than the single, unified body had presented. So the mass/drag ratio shifts dramatically towards the drag side of the equation, and all of the individual pieces fall uprange of the protected capsule.

Now, if the stage contained a nice cylindrical fuel tank that was both relatively massive (representing a fair fraction of the total mass of the stage), and that tank were made of a heat-resistant metal like beryllium, the tank (being a nice aerodynamic shape) would fly on to the farthest downrange end of the debris footprint. But even so, its mass/drag ratio profile would still probably have it falling uprange of the landing site.

-the other Doug

So basically we should be scouering MOC images west of the landing site in this release - http://www.msss.com/moc_gallery/r10_r15/mc19.html - and the next release due very soon. The landing site is near the top right - you can tell from the little strip of lots of MOC images. At the moment - most of the images in there are pre-landing - but the next release will all be post-landing.

Doug

Thorough (and well done) analyses "other Doug", though, didn't you forget that the footprint of debris must have overtaken MER, because of the parachute she landed with ?

I dont think they'll have spent very long going downrange on the chute - from chute deploy onwards it's mainly downward motion - but as I said - I think it's best to look up range, down range, left range, right range - it could be anywhere

I think Gusev will be an easier 'spot' as the surface is much brighter and the sub-surface much darker than at Meridiani.

Doug

I'm not convinced that one will be harder than the other. Both of the heatshield impacts made very distinctive darks spots on the MOC images:

Spirit http://www.msss.com/mars_images/moc/2004/01/23/

Opportunity http://www.msss.com/mars_images/moc/2004/01/23/

In fact, Meridiani is so featureless it may make spotting disturbances eaasier...

Chris

Could the dark splotch east of our recently visited crater triplet be the imapct of surviving CS components?

(http://www.unmannedspaceflight.com/index.php?act=Attach&type=post&id=355)

-- Pertinax