NASA Set To Launch Probe To Mercury

antispam_ben writes "CNN is reporting the upcoming Messenger mission to Mercury is set to launch August 2. The spacecraft uses a combination of technologies (insulation, Peltier devices, careful design and orbit, always keeping the shield side toward the Sun) to keep its electronics at room temperature."

Comments

room temp?

[Anonymous Coward]

Is room temperature an actual degree? I always thought it was just the temp of the envirnment that the time. If that's the case, room temp for the spacecraft is pretty hot no?

Very interesting.

[robslimo]

I know thermal issues have always been central to spacecraft design, but this sounds like a nicely engineered approach to temperature control.

I'm reminded of the faulty heater on one of the Mars Rovers. Could such problems be avoided or at least mitigated by use of more passive thermal management (insulation, heat pipes, heat sinking/sourcing)?

I'm also reminded of the Russian probes to Venus which had uderstandably short lives due to both heat and pressure (possibly corrosive gases as well).

I'm firmly in the camp that promotes more unmanned probes, maximizing the power of money spent on advancing spacecraft technology and knowledge from expanded exploration rather than blowing it all on the dubious value of letting a person stand on Mars.

Explanation

[Timesprout]

Even though Mercury is 50 million miles from Earth at closest approach, Messenger will travel 5 billion miles to get there. It's technologically infeasible to fly straight to Mercury, a trip of a few months, and so the spacecraft must swing once past Earth, twice past Venus and thrice past Mercury before slowing down enough to slip into orbit around Mercury.

Can someone explain why such a convoluted and time consuming route is required?

Anyone else reminded of Brin's Sundiver

[merlin_jim]

I like their cooling solution much better; high temperature superconductors and peltiers to move the heat to a central location, where the kinetic energy is used to power a communications laser.

Too bad our current superconducting technology is scaling more slowly the higher temperature it gets. What we're currently calling "high temperature" means room temp. We'll make it there eventually. But without a whole new technology (nanotech anyone?) we'll never make superconductors that remain super conducting at temperatures much higher than that.

But what about a laser powered by heat? Can it happen without having to reach the ionization temperature of the lasing medium? Anyone have any insight?

Re:Anyone else reminded of Brin's Sundiver

[merlin_jim]

When you do that the white side absorbs only a little of incoming heat, and then it is transferred by contact to the black side, which transmits the heat away pretty well.

Hmmm... maybe phase-change solid-state heatpipes would help this even more; integrate them directly with the material of the ship...

As a matter of fact that may be a good technique for any space ship, to guarantee that no part of the ship gets too hot or too cold.

Re:Anyone else reminded of Brin's Sundiver

[Ignignot]

I am not sure heatpipes would work because they use different densities of the heat transfer medium (like water or air) to cycle it. While the mediums will still have different densities, they won't move at all because there would be no gravity. I guess you could spin the spacecraft, and that would produce a similar effect. However I think that the movement of the medium would eventually screw up the spin of the spacecraft until it became an uncontrolled tumble - bad. You could counteract this with gyros or thrusters I guess. Complicated. :-)

Re:Room Temperature

[Waffle Iron]

I would hope they would make it come down to that temperature, I don't know of any kind of insulation that would actually do that.

It shouldn't be all that hard since in space thermal control based almost solely on radiant energy. Even though the side facing the sun will get very hot, the side facing away from the sun is exposed to empty space with a temperature near absolute zero. If you simply reflect most of the sunlight away on the hot side, slow down what gets absorbed with a little insulation, and arrange to radiate what does get through the insulation (along with any internally generated heat) on the cold side, you should be able to maintain a reasonable temperature.

From what I've read, one of the hardest parts about controlling temperature on this probe is to handle the times when it passes in front of Mercury. Then, the near-zero chill on the "cold" side is temporarily replaced with the radiant heat from the > 400 C surface of the planet. At these times the probe has to be closed up like an ice chest to maintain its internal temperature at reasonable levels until it gets away from the planet.

The really amazing thing...

[Anonymous Coward]

...isn't the 5 gigamile trip. It's the launch window. They have a 12 second launch window to either launch it or wait for the next 12 second window-- the next day, at the earliest. Because of the multiple fly-bys, the math gets a little complicated, and error tends to cascade towards failure.

Talk about performance anxiety!

Wife: OK Honey, I'm ready. You've got 12 seconds.

Enough for a high school boy, I imagine, but not us mighty slash dotters, right? ;-)

Re:Room Temperature

[Rei]

Thank you for saving me the time. Some people just don't get that, on a spacecraft, you're dealing with a near closed system here apart from solar input. No matter how much insulation you have, if you're not A) reflecting the solar radiation away, or B) radiating the heat away from your craft, you're going to burn up.

Thinking that you can simply insulate a probe enough to handle solar radiation is like thinking that you could swim in a volcano for weeks if only you could find a good enough type of insulation. The insulation for the probe is to help reduce the effects of heating/cooling cycles, not to keep the probe's temperature down.

Re:Good Candidate for outsourcing

[antispam_ben]

You see all these people working on these satellites wearing protective clothing, not to protect the people but to protect the equipment.

Often it's to protect both the people and the equipment from each other. You may recall the "bad day" a year or rwo ago when a 200 million dollar sattelite under construction fell over (because someone took the platform mounting bolts to use in another project without documenting the removal, and later when they tilted the platform...). Some of the pictures I saw showed yellow tape around it to keep people out, as there was fear that some of the sealed gases would leak from damaged tanks.