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Mars Sundials - True Colors, Ambiguous Hours
An anonymous reader writes "NASA's Astrobiology Magazine today has an interview with Bill Nye, the Science Guy, who spearheaded the first interplanetary sundial, which will land on Mars in early January. The Cornell sundial inscription reads "Two Worlds, One Sun" in 17 languages [including ancient Sumerian and Mayan], and was selected over such historical mottos as one French sundial that reads: "Every hour injures; the last one kills". The sundials were an inspired transformation of a needed [mainly orange-pink] color wheel to calibrate the Mars' panoramic cameras to give true Martian colors, but so resembled the shadow-casting time pieces, that Nye took it over to become an internet-updated interplanetary dial." Read on for some more.
Our reader continues: "There are no conventional hour lines at all on these dials, because unlike regular sundials, they are on moving platforms. Nye says: 'Before people figured this out back in the first era of Mars probes (also the first Disco Era) the images from the Viking spacecraft were too pink or orange. Those "over-pink" images still show up in Mars science fiction movies and Mars-themed posters and restaurant walls. One of the charming challenges is roughly, "What is an hour on Mars?" Is it a "Mour?" Is it a "quadraduodeci-sol," a twenty fourth of a sol, a Mars day? ' The interview recounts the Apollo 12 controversy over whether one of the first lunar probes, Surveyor, returned viable contaminants to Earth."
http://www.giss.nasa.gov/tools/mars24/
Actually, according to the article (there's even a picture where this is visible), the inscription "Two Worlds, One Sun" is in English only, and the word "Mars" is in 17 languages.
Following a few links from the mission site, I found the answer to a question I had about the communications capabilities of the rovers.
n s.html
They can communicate directly back to Earth at a slow speed ( 3,500 to 12,000 bits/sec ) or they can communicate via the Mars orbiting spacecraft (Odyssey or Mars Global Surveyor) at a rate of 128,000 bits/sec. The orbiters are only 250 miles from the planet surface.
Unfortunately, there was no information about protocols, encoding, or error correction schemes..
Some good info is here: http://mars.jpl.nasa.gov/mer/mission/communicatio
BTW, the simpler design of the Kalashnikov AK-47 rifle was what enabled the Vietcong to prevail over American soldiers equipped with the Stone M-16, which was more advanced.
That's another myth. It was bad politics, plain and simple, that allowed the Vietcong to prevail. You try fighting a war where you can't bomb their factories, not allowed to destroy their air bases, weapon depots, or radar stations. You try winning a war where you can be jailed for actually attempting to win. You try winning a war were most of the S. Vietnam officials were corrupt and giving bad intelligence; the US knew full well this was the case but still continued to heavily use it. Toss in non-professional soldiers and it couldn't of been won with God's own hand. All that, without even talking about the tactics that the Vietcong used.
Once the bullets were changed back to their proper powder, and cleaning kits were finally issued, the m16 proved it self. Likewise, before it was officially issued and cleaning kits were made available and proper ammo was being used, it was in high demand by special forces and other elite units on the ground for "instruction" and "training". The reason being, it was fairly accurate even to extreme ranges (for open sights), light, and they could carry a lot more ammo.
The AK, on the other hand, could be tossed in the mud or in a rice field, let rust, kicked open, and be ready to fire in combat. It's accuracy at medium to long+ ranges *significantly* suffers because of this. This generally wasn't a problem for the Vietcong because combat was generally was short and hand-to-hand ranges.
I suppose you mean 'propulsion allowing a higher terminal speed'. Todays chemical rockets are basicly 'burn, then coast'. You accelerate a lot for a while, then glide towards the target. A ion-engine or a nucular rocket will let you accelerate less but for a much longer time, meaning you'll get a higher terminal velocity. The providial Holy Grail for interplanitary missions would be an engine which would let you accelerate forever. Just think about it; you blast off into orbit, then turns on the flightengine. That gently accelerates you to one G.. and keeps that accelatation all the time. Halfway to the target, you simply turns around and deacceleate with one G, leaving you with zero relative speed as you enter orbit around Mars (or wherever you want to go). The speeds you'll reach are way higher than any chemical rocket can provide, the flighttime shortens and we don't have to worry about the determinal effects of living in zero G for years on end. I havn't got my notes and calculator here right now, but maybe someone could punch up some numbers on this?
.5 * acceleration * time^2 .5 * 9.8 * time^2
This is an easy one.. Okay, Mars was at it's closest a few months ago, right? A quick google tells me that it was 55.76 million kilometers away at the time.
So, since we're accelerating to there and then slowing down halfway, basically we divide the problem into two parts. How long will it take to get halfway there? Then we simply double it to get the reverse, how long it'll take to slow down.
-Half of 55,760,000,000 meters is 27,880,000,000 meters.
-One G is 9.8 m/s^2
Distance traveled =
27,880,000,000 =
Solve for time, and you get 75430.73589... seconds. But that's only halfway to Mars, so double it to get the slowdown part too and you have 150861.4717... seconds. Divide by 60 for minutes, divide by 60 for hours, and you come up with roughly 41 hours, or about a 1 and 3/4 days total.
So yeah, if you had all the delta V you could handle, you could be there in under a couple days.
Too bad we don't have that.
- Give a man a fire and he's warm for a day, but set him on fire and he's warm for the rest of his life.
If I recall, Bill Nye was a character on a Seattle-based comedy show called "Almost Live". He's actually educated, but the whole "Science Guy" character came from a comedy show. (And the kid's show started there.) And now he's heading up projects like this???
That was about 15 years ago, so maybe people who remember will remember more clearly and call me an idiot. Other Slashdot readers will probably call me an idiot regardless...
Here are two very pretty photographs of the analemma - composite photographs of the sun taken at the same time and place every few days for a year, and a simulated martian analemma