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Mars Landers - Opportunity, Bedrock, Aerosmith?
Iphtashu Fitz writes "As was reported last week, the first Mars rover Spirit had some communications problems that the folks at the JPL have finally managed to trace to problems with its flash memory. Reuters is reporting that Opportunity seems to be having some power-related problems, too. It appears a faulty thermostat is turning a heater on overnight without being told to do so. While NASA isn't concerned about the rover overheating, they're exploring the long-term effects of continued power drain on the second rover." The article also notes: "The first three-dimensional, panoramic images beamed back from Opportunity showed an intriguing outcrop of exposed bedrock" - there's now a color version of the same image. Finally, lightwaveman points to the Spaceflight Now status page regarding new priorities for the Mars mission: "The airing of today's Mars rover news conference is being delayed on NASA TV to show the band Aerosmith touring International Space Station Mission Control at Houston's Johnson Space Center."
Why do we need to go there at all? So we can turn off switches that fail on the stuff we bring there to do actual work cause it is too harsh for people to do? I would like it if someone could give a real scientific or at least monetary reason to send people to mars.
Ha, while that is true for the Earth as a whole, it might add politically significant amount of uranium isotopes to some dude's backyard in Florida and that counts 100x more than all the output of coal plants combined globally.
Did you know that uranium is one of the most common substances on Earth? You probably already have some in your backyard. Raining some from an engine would NOT increase it by that much. It certainly wouldn't kill you in the time it takes for the nuclear energy commission to clean up your neighborhood.
Did you know that old style X-Ray machines would give you up to 10 REMs of X-Ray radiaition per X-Ray? Modern digital machines give off only about 10-100 millrems, but if you are older than 15 you may have had an X-Ray from an older machine.
You'll note BTW, that it did not instantly kill you or cause your skin to melt. In fact, doctors considered it quite safe as long as they made sure not to give you too many X-Rays.
When it comes to nuclear power, the real dangerous stuff is the heart of a very large reactor. Older reactor designs would keep hundreds of pounds of material under pressure so that they could produce large amounts of power. In the case of a melt-down and boiler explosion, a lot of hard radiation would be exposed to people near by. (And I mean people within about half a mile. Radiation falls off at the same rate as light, so give it just a little distance you won't get any more than you would from your CRT.)
Here's the upside about the "hard stuff". It doesn't last. In order to be energetic enough to kill someone, it has to have a very short half-life. Within an hour, a reactor's core has already lost much of its most potent stuff. Within a few days it may even be safe enough to approach. Within a month they could cement over it and forget it existed.
I should probably mention that modern reactors can't have a boiler explosion like Chernobyl. Those designs were deemed unsafe long before the incident, and were decommisioned here in the US. Chernobyl OTOH, was built with *decreased* safety precautions because the Russians thought they were unnecessary. Contrast that to Three Mile Island which shut down exactly as it was supposed to.
Some interesting statistics for you. Currently, there are ~500 nuclear reactors in the world, plus the 50+ used by US Navy Vessels (8 on the Enterprise alone, 2 on a standard Nimitz carrier, and 1-2 on each nuclear sub), plus about 550 research reactors operating worldwide. Nuclear reactors are well understood things at this point.
I must admit that from what you are describing the engine would look completely different from what I have seen in some old magazines, it must be some completely new concept, if you have some links to sites (with pretty diagrams for ignoramuses) I would appreciate.
Wikipedia explanation of various proulsion methods
NERVA and GCNR engine descriptions
You're probably thinking of NERVA engines. NERVA engines would melt off the back of a rocket and drop from the sky like a rock (a very heavy rock) if they were to melt-down (although they run pretty close to melt-down normally). Gas Core Nuclear Rockets (GCNR) use a uranium plasma vapour for heating the propellant. This is in many ways easier to contain in an emergency than a tradiational nuclear pile.
BTW, I should probably point out some of the safety features of nuclear rockets. For one, they have more power, so they can be built of more traditional and well understood materials. Many chemical rockets go for exotic composites to keep weight down. The other advantage is that the fuel is what cools the engine. In the case of a runaway nuclear reaction, the turbopumps can deliver more fuel to cool the reactor
Javascript + Nintendo DSi = DSiCade