How to bring a 3.3 tonne laboratory from 21,240km/h to zero in 7 minutes...

[SLATYE]

Having a "charging station" would also seriously reduce its range.

The old rovers (Spirit and Opportunity) can't store much more power than is necessary to keep them working overnight; they need to recharge during the day. Curiosity has batteries too, but they're only for when it's doing something that exceeds the RTG's output - they're not designed for sustained use.

Even if they packed Curiosity with enough batteries to run for a few months, it'd be restricted to working within a few kilometres around the charging station. At 200m/day, a few months is not very much exploring.

Finally, if it ever got stuck, that'd be the end of the mission since it'd go flat before it was able to get 'home'. It took NASA eight months to analyse Spirit being stuck in soft soil; by that time the information would be useless as the rover would be dead.

With solar cells on the vehicle (as with Spirit and Opportunity) or the onboard RTG (as in Curiosity), there's no real time pressure - you can keep trying stuff indefinitely. Even if it actually cannot get moving again (as happened with Spirit) the rover can do experiments in-place until something else fails.

[Agg]

What I never understood about Spirit/Opportunity was why they didn't equip them with solar panels that could be tilted or vibrated to get dust off them. Maybe it's only obvious in hindsight.

[Doso]

Originally Posted by Agg

What I never understood about Spirit/Opportunity was why they didn't equip them with solar panels that could be tilted or vibrated to get dust off them. Maybe it's only obvious in hindsight.

You have to remember that Spirit/Opportunity were only designed to work for 90 Sols and that's it, both rovers exceed this by many MANY times over. In fact Opportunity which is still working just ticked over 3000 Sols!

Where as Curiosity has been designed from the ground up to work for a long design time that's why it uses a RTG rather than solar cells as you said your not restricted by solar cells and the associated problems

[SLATYE]

Originally Posted by Doso

You have to remember that Spirit/Opportunity were only designed to work for 90 Sols and that's it, both rovers exceed this by many MANY times over.

As far as I can tell, they were designed to work for 90 Sols because NASA knew that after that time, the solar panels would be covered in dust and wouldn't provide enough power for continued operation.

This makes Agg's question all the more relevant - if NASA knew that dust on the panels was likely to be what limited the mission length, surely it'd make sense to deal with that.


Tilting solar panels would seem like a logical option, since that also means that they can tilt them to catch the sun better. Instead they ended up parking the rovers on slopes in order to keep the solar panels tilted.

[Airquarious]

Originally Posted by SLATYE

Tilting solar panels would seem like a logical option, since that also means that they can tilt them to catch the sun better. Instead they ended up parking the rovers on slopes in order to keep the solar panels tilted.

...or maybe a little compressor to blow the dust off.

[MoorKhan]

Originally Posted by Old MER QandA session

A brush or wiper system would require too much mass and probably wouldn't do a very good job of getting rid of martian dust. The particles are only about 1-2 micrometers in size.

Presumably the same thing stopped them installing a tilt system. The solar panels are pretty large relative to the rovers, so installing something that would clean or tilt them would cost them a lot in mass that was better used on other things.

One of the interesting things about Curiosity being powered by an RTG is that it highlights the current shortage of plutonium-238. Supposedly no one has being making it for years, the US stopped in 1988 and ran out in 1993. Until recently they've been buying it off Russia, but Russia is running out now and has stopped selling it.

Apparently the US have enough left to get them through the next decade of scheduled missions, but beyond that they'll be stuck. Without p-238 they wont be doing any deep space missions or basically any planetary probes. Even the solar powered Spirit and Opportunity still required p-238 heater units to function (and Mars is a pretty friendly destination for solar powered vehicles). They could use an alternative heat source in RTG's and RHU's, but nothing else really compares to p-238.

Ten years seems like a long time, but restarting production has an (optimistic) 5 year lead time, and the current ten year supply assumes no changes in demand over that period.

[Danske]

What I meant was instead of just crashing skycrane into the ground, make it do something else .

Would have been great if it could have gone and fished spirit out of the ground! .

And yes I know what I'm saying is ridiculous on an enormous scale, but it's fun to just talk about.

[kombiman]

Originally Posted by Danske

What I meant was instead of just crashing skycrane into the ground, make it do something else .

Would have been great if it could have gone and fished spirit out of the ground! .

And yes I know what I'm saying is ridiculous on an enormous scale, but it's fun to just talk about.

I'm with you, an interplanetary bump start! I wonder how far they are from the other rovers? It sees also a waste that they didn't try and land the crane too, then film from it or something.

[SLATYE]

Originally Posted by Danske

What I meant was instead of just crashing skycrane into the ground, make it do something else .

They'll probably drive over and have a look at the crater. That might prove useful.



Realistically, NASA probably did look at what they could do with the skycrane. I'd guess that they decided that anything they could do with sensors on the skycrane would be done better by mounting the same sensor on Curiosity instead. After all, the skycrane only had a few seconds of fuel left after delivering Curiosity, so the amount of information it could gather would be very limited.

[Danske]

Originally Posted by Agg

What I never understood about Spirit/Opportunity was why they didn't equip them with solar panels that could be tilted or vibrated to get dust off them. Maybe it's only obvious in hindsight.

Yeah similar to how some DSLR's vibrate the sensor to get any dust off...

I do recall reading small dust devils on Mars helped clean the rover's panels a few times.

[shift]

Originally Posted by SLATYE

They'll probably drive over and have a look at the crater. That might prove useful.

Nope, they've said they're going to stay well away from it. There's actually quite a bit of fuel still in it, so they consider it hazardous.

[tornado33]

Now that most of the full resolution raw Mars Descent Imager pics have been posted on the JPL site,
http://mars.jpl.nasa.gov/msl/multime...0&camera=MARDI
I downloaded them all and made a spectacular high definition video of the descent and landing.
Here it is at 30 fps
http://www.youtube.com/watch?v=h-d2o...2&feature=plcp

and at a slower 15 fps

http://www.youtube.com/watch?v=18v7F...1&feature=plcp

For best results select "original" video quality and you will see the movie at native resolution.

JPL made it easy to do as they sensibly name all the images in numerical order. I used Flashget to download them in batches, then a freeware program called Photolapse to make the video. It reads the images names and assembles the video in minutes.
Cheers

[pduthie_au]

That's pretty cool work. Great viewing.

[tornado33]

No worries, happy to share the videos.
Im surprised NASA/JPL hasnt made and published a video of their own of the descent. I guess they are flat out preparing Curiosity for surface operation. Looks like the Chemcam system is a goer too, the laser works ok. Looking fowards to the start of driving.

Re the descent we can tell when backshell sep. happens and the descent stage tips over to move away from the parachute/backshell, then literally locks onto the ground with the Terminal Descent Sensor and descends vertically with no horozontal movement at all. Right at the end lots of dust and some small rocks are seen flying about. Thankfully the Skycrane descent stage was relying on data from the Terminal Descent Sensor rather than the camera to gently lower Curiosity to a perfect gentle landing.

[Braedz]

Absolutely amazing, good stuff tornado33