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There is a cool article today in New Scientist that describes an old cooling method with a bleeding edge application: a rover to Venus. Venus is a picture of the greenhouse effect gone wild. Average temperatures are about +260 degrees Celsius (500 degrees Fahrenheit). This is hot enough to melt lead and destroys most modern electronics. Previous rover attempts to Venus by the US and Russia lasted less than 2 hours. So if we are to put a rover on Venus for the kind of time we have spent on Mars, we’ll need to find a way to cool the onboard electronics long enough that they can operate well.
Enter two NASA boffins, Geofferey Landis and Kenneth Mellott. By applying a refrigeration technique invented by a clergyman nearly two centuries ago, they have found a way to keep a rover cool for about fifty Earth days (a Venutian day is 243 Earth days, about 19 days longer than its year!). The Stirling cooler (invented by Reverend Robert Stirling) works by compressing a gas with a piston. As it compresses, it gets hotter. The temperature is dissipated with a radiator (which would be placed on the back of the probe). As the gas expands, it gets cooler (causing the refrigeration effect). In order for this to work, the radiator must be hotter than the outside air.
Interestingly, the Stirling cooler is energy efficient and is being incorporated into some of the newer energy efficient refrigerator models. To power the cooler on the rover, they propose using a plutonium battery. This type of device is known as a radioisotope thermoelectric generator. As the radioactive material decays, it release heat, and this heat is converted into electricity. These batteries are common on satellites and in unmanned situations where a long duration power source is necessary and solar cells are not viable (the massive cloud cover on Venus prevents solar cells from being very effective, plus the atmosphere is very caustic and I think it would probably damage them).
Well, if there is somehow intelligent life on Venus, let’s hope they don’t confuse this rover for the first case of interplanetary terrorism.
Which will be the newest extraterrestrial body humans will set foot on? (Aside from the moon, of course.) According to Pascal Lee of the Mars Institute, “[Phobos and Deimos] are the most accessible planetary bodies in our solar system.” New Scientist has a report on the conference at Ames Research Center on Wednesday where ideas were thrown around for the human exploration of Mars. Astronauts could set foot on one of them within a decade. So cool.
Phobos and Deimos are similar in nature to C-type asteroids. Phobos is porous and has an extremely low orbit, subjecting it to tidal forces. These forces will eventually cause it to either break up or crash into Mars (in about 30-80 million years). In the meantime, it would make an excellent base of operations for a manned mission to Mars. Escaping the gravity of Phobos or Deimos would be much less difficult than escaping that of Mars.
One of the biggest problems with such a venture according to the New Scientist article is dust. With such a weak gravitational field, Phobos could have as much as 5 meters of dust accumulated on its surface. Also, a long journey like this would expose astronauts to too much radiation, giving them a 5% chance of dying of radiation poisoning (above the 3% NASA allows). But wouldn’t it be cool, to stand there on that dusty rock, a mere 6000 miles above Mars, looking at that giant red orb in the sky?
There is a somewhat rare opportunity for people in the US and southern Canada over the next two days. The space shuttle Discovery just undocked from the International Space Station and is currently drifting just in front of it. It will be passing nearly overhead just before dawn, the best time for viewing. As the space station comes into the sunlight while the Earth below is still in darkness, the solar panels reflect the light and it stands out brighter than most stars in the sky. Both the ISS and Discovery will be visible to the naked eye. In fact, the ISS is four times brighter than the brightest star in the sky and about equal in brightness to the planet Jupiter.
To see when the space station will pass overhead, check out the NASA Skywatch website. You can also use the most excellent real-time satellite tracking website, n2yo.com. I mentioned this website before, and it continues to impress me. You can create prediction maps for up to 5 days in advance, showing exactly where it will pass near you. Tomorrow morning at 6:12am, Pittsburgh will have a very nice, nearly overhead view of the ISS and Discovery.
Discovery lands Wednesday around midday, so your chances for viewing are limited to Tuesday and Wednesday (Nov 6th & 7th).
I caught Randy Pausch on Oprah yesterday (and yes, a dying CMU professor IS the one of the few things that will make me endure watching Oprah). His last lecture focused on the importance of childhood dreams and he mentioned the landing of men on the moon as a pretty fundamental motivator. Heck, it inspires me still and I wasn’t even alive. So I especially love it when NASA gets kids involved in the space program (I’ll return to this after a brief rant). Too much today, launches of the shuttle, the existence of the International Space Station, and probes sent to other planets are just routinely ignored or sidelined by the mainstream press. Discovery launched today carrying the Harmony module to the ISS and it got about 3 seconds on the Today show. The result? People think the space program is totally useless. It doesn’t help when Nobel laureates like Stephen Weinberg call the space station an “orbital turkey” that “has produced nothing of scientific value.” That brings to three the number of Giant Turds with Nobel Prizes (joining James Watson the Racist and Al Gore the Murky-Green Fraud). For a nice rebuttal of the Weinberg gibberish, there is this article from adAstra that mirrors the point by Randy Pausch a bit.
Anyhow, returning from my rant. NASA has announced a contest for school kids to name a place for the Cassini probe to point. Cassini is currently in the Saturn system. It recently left Iapetus, which I indicated looks like the Death Star. Currently it is focusing on Saturn’s moon Titan and will be doing some close flybys of it over the next few months. For students to participate the contest, they need to write a 500-800 word essay on why Cassini should look at one of four possible targets on November 30, 2007. So if you know a kid in grades 5-12, let them know.
Four Targets:
- Mimas (a moon) coming out from behind Saturn
- Saturn’s rings and a lot of moons
- Prometheus (another moon) and the F-ring (Prometheus seems to actually steal matter from the ring)
- Tethys (yet another moon) and its Odysseus impact basin
The shuttle Discovery is set to launch Tuesday to bring the Harmony module to the International Space Station (ISS). The Harmony module, named by US school kids, is a connector that will bring together the various international components of the space station. Specifically, it will connect the US Destiny Lab, the ESA’s (European Space Agency) Columbus module and Japan’s Kibo module. The Italian-built Harmony module has been sitting in drydock since 2003, where it underwent pre-flight preparation.
If you were going to build a death star, then hide it, what would it look like? SciAm Observations today has an array of desktop backgrounds of the moon Iapetus, which orbits Saturn. Iapetus is an especially fascinating moon for many reasons. For starters, it has a giant impact crater. Also there is an equatorial ridge which encircles the entire moon, making it slightly resemble a walnut. The moon is heavily pockmarked with craters.
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Image courtesy of NASA and JPL. Taken by the Cassini probe. |
Wired has announced the winners of the NASA slogan contest they were running a while back. As I said in a previous post, I made a submission, but not long after doing that I soon regretted it. My choice of slogan was more of a sci-fi joke, so had no chance. I thought it was at least mildly amusing, but it got voted down pretty harshly, so apparently not.
“Earth is not room enough.”
So the winners were announced today and they aren’t bad. The top 3 are:
- Exploring Other Worlds, Understanding Our Own
- NASA: Explorers Wanted
- NASA: Bringing the Universe to Your Doorstep
Well, they aren’t great. The first choice is definitely my favorite of the three. They also listed the entire top 25, but I won’t reproduce them all here. My favorites of those are:
- Fueling Imagination
- Innovation Through Exploration
- The Universe is Waiting
And my favorite amusing entry:
- Ad Astra, Per Asparagus
NASA’s image of the day is the Dawn spacecraft launching via a Delta II rocket. It’s heading to two asteroids: Ceres (actually a dwarf planet) and Vesta. The journey will take several years. In March 2009, Dawn will slingshot around Mars to arrive at Vesta in September of 2011, where it will stay for about seven months. After that it will head to the dwarf planet Ceres, a journey of three more years, arriving in February of 2015. Five months later, the primary mission will end.
The Dawn spacecraft will be using an ion propulsion system. This allows the spacecraft to travel with much less weight. An electrical charge is used to accelerate Xenon atoms at rates 10 times faster than chemical fuels. Because the force it takes to accelerate something depends on its mass (F = ma), the lighter (less massive) a spacecraft is, the less it takes to move it. Petroleum is heavy, so using it for a spacecraft really doesn’t work very well, but it is used for launch vehicles like the Delta II rocket. The petroleum used is known as RP-1 (Refined Petroleum) and is mixed with liquid oxygen. The ion propulsion drive is fuel efficient but not exactly speedy. No one is going to brag about 0 to 60 mph in 4 days. The bonus is, the spacecraft only uses 10 ounces of fuel per day at full burn. At that rate, Dawn can go about 1500 days, but it won’t need to be at full burn every day.
The Dawn spacecraft is currently sitting on the launchpad at Cape Canaveral, where it will wait until September 26th for launch. NASA always chooses these vague, optimistic names for spacecraft. The Mars rovers have names like Spirit and Opportunity or old probes with names like Voyager and Pioneer. Of course there are the dreadfully functional names like Mars Polar Lander. And of course, the odd barbarian always finds his way into the crowd: Viking. But I think that Dawn is named well. Here we have a spacecraft that is actually going to the asteroid belt and examine the asteroid Vesta and the dwarf planet (ala Pluto) Ceres. Of course, Ceres is a smidge smaller than Pluto having a radius of 475 km versus Pluto’s 1153 km. The great thing about asteroids, though, is that their escape velocity is relatively minor. Ceres is only 1.2 km/s, or about 4320 km/h (2685 mph). This is nothing when you consider the escape velocity of Mars is 18,097 km/s (11,247 mph). The bonus here is that spacecraft going to Ceres expend less fuel in their approach (slowing down) and less fuel on take-off.
Dawn will only be orbiting these bodies, not landing on them. Dawn’s mission is to study the formation of these two objects, but I think the longterm effects are much more important. For one, it will give us experience in working with the asteroid belt. Many sci-fi writers have speculated that the asteroid belt will be a great place for space stations and mining operations. If Dawn finds the right things, it could spur further exploration of the asteroid belt. Maybe one day my great grandchildren will visit the space mining museum on 243 Ida (below) and spend the night at the bed and breakfast on its moon Dactyl (the speck on the right).
NASA is looking for a new slogan and Wired wants one of its readers to be the one who comes up with it. Vote for mine or come up with your own. My proposed slogan is “Earth is not room enough.”
As a big fan of both Star Wars and the International Space Station, you would think that the upcoming marriage of the two would delight me. You would be wrong.
Luke Skywalker’s lightsaber will be flown to Houston, where it will be sent off by Chewie and a host of other minor Star Wars characters, including R2 and some stormtroopers. Then, it will be carried along with the new Italian-built Harmony node to the space station by STS-120 (Discovery) on October 23rd. At the end of the mission, it will be brought home and probably gain a few tens-of-thousands of dollars in value as a result. The reason for this gimmick is the 30th anniversary of the Star Wars franchise.
I suppose the reason I hate this cheap, pointless exercise so much is that I am really angry with people not appreciating the sheer awesomeness that is the International Space Station. Most Americans would be shocked to learn that there are currently people living in space. The fact that they don’t already know it says to me that something has gone horribly wrong in our national psyche. So NASA feels the need to allow this gimmick to proceed, perhaps in hopes of increasing awareness and therefore funding. Maybe it’s not so much anger I feel as it is sorrow, for the futility I sense in trying to change the status quo with such a cheap trick.
Or maybe I’m just being way too dramatic — a charge that has oft been levelled at me. I will not deny it. Probably the LucasArts people wanted to generate some buzz for their franchise and the NASA geeks, having a high probability of being devoted Star Wars fans, accepted gladly.
Space.com: “NASA Shuttle to Launch Luke Skywalker’s Lightsaber”
While I’m not usually into endorsing anything related to Microsoft, they do appear to have a rather cool offering with Photosynth. It uses multiple images to compile a three-dimensional representation of the subject. I’ve used the firefox extension to look at the Shuttle Endeavor from many different angles and many of the pictures are high-res enough that you can zoom in and see the shuttle up close and personal. Worth a few minutes examination, at any rate.
Microsoft Photosynth: http://labs.live.com/photosynth/
Shuttle Endeavor: http://media.labs.live.com/photosynth/NASA/default.htm
