Scientists Give NASA Planetary Marching Orders 145
coondoggie writes "The community and team of scientists that help NASA prioritize space missions has come out with its exploration recommendations for the next decade: get to Mars, explore one of Jupiter's moons and study Uranus. From the report: 'The gas giants Jupiter and Saturn have been extensively studied by the Galileo and Cassini missions, respectively. But Uranus and Neptune represent a wholly distinct class of planet. While Jupiter and Saturn are made mostly of hydrogen, Uranus and Neptune have much smaller hydrogen envelopes. The bulk composition of these planets is dominated instead by heavier elements; oxygen, carbon, nitrogen, and sulfur are the likely candidates. What little we know about the internal structure and composition of these "ice giant" planets comes from the brief flybys of Voyager 2. So the ice giants are one of the great remaining unknowns in the solar system: the only class of planet that has never been explored in detail.'"
Re:Develop spacefaring technology first (Score:4, Interesting)
from what i read on wikipedia, temperaturs vary between 100k and 700k, with the 100k representing the permanently dark side of the planet and the more common temperatures in the non-dark regions being around 400-500 K
Temperature wise, i would much prefer Mars, which is (once again, according to wikipedia) -85 (~200K) to -5 (268K) degrees centigrade
Both pretty much SUCK in terms of atmosphere, and mercury would win in terms of available (solar) energy, but i'd much rather bring some extra solar panels to mars (or a nuclear reactor..) then risk being boiled on mercury.
I agree though that we need to explore those rocks out there, titan and europa are interesting indeed, but as a first off-world settlement, i would think mars is a better place to start then mercury
Re:Develop spacefaring technology first (Score:4, Interesting)
If ice is found at one pole of Mercury a mission could land there and use local water. Temperatures at the pole would not be too bad. Remember those are surface temperatures. They will affect gear left out in the sun, but the real problem will be solar heat soaked up by pressure suits and habitats. If you make them highly reflective your main heat problem will be from people and equipment inside. Apollo used open circuit cooling by sublimating ice. A mercury mission could work the same way.
The slow rotation of Mercury means that astronauts could explore the whole planet by following the terminator. Each traverse would start at one pole, cross the other and finish at the starting point.
The problem with Mars is that pressure suits would have to use a lot of energy keeping their occupants warm. Batteries have limited capacity so EVAs will have to be short. I reckon that gear used on Mercury could be directly derived from gear used on the moon.
Re:Develop spacefaring technology first (Score:5, Interesting)
There is no such thing as 100% reflective. and if you do achieve that, dirt will accumulate and transfer heat via conduction. Any person in a suit standing on the surface of mercury that is in the light will cook lie they were in a rotisserie even wrapped in 100% effective mirrors. Its surface ranges in temperature from -270F to 800F (-168C to 427C) and it's day is insanely long, the poles do not matter. you need to be in a deep crater out of the sunlight. Here's another problem, the sun takes up much of the sky, it's not that tiny bright disk in the sky like we have here, you have a giant bright as hell 50% of the sky ball of fire. you are also within the sun's magnetosphere so good luck with electronics. How do you design solar panels that can not fry in that environment? Actually you do it differently, large black panels with thermocouples. use the temperature difference between light and dark.
Mariner 10 was designed for the high heat by giving it a high temperature heat shield to shadow the craft from the sun, it also had very hardened electronics and still had problems. The on-board computer experienced unscheduled resets occasionally, they had to reconfigure the thing several times to salvage the spacecraft. The attitude control systems also flaked out and used up a bulk of the fuel on-board. Operating that close to a star is highly difficult and dangerous even for robotic missions.
Re:Develop spacefaring technology first (Score:5, Interesting)
Mars may not be the best place for humans to go. Mercury for example looks positively inviting in comparison to Mars.
My apologies to throw in some facts on to your dreams, but I wouldn't call Mercury "more inviting".
Atmosphere - 1 nanoPascal (blown away by solar wind), a magnetic field at 1% the terrestrial one => very little protection against hard radiation [wikipedia.org] With an eccetric orbit, the Sun's radiation intensity is between 4.59 and 10.61 times the level on the Earth orbit (on the surface of Mercury, the Sun looks on average almost three times as big as it does from Earth).
Not having a significant atmosphere, there are no chances for aero-breaking. The delta-v between the orbital-speed is 18 km/s that need to be lost for reaching a transfer orbit. Even more, a space vehicle will fall into the Sun's gravitational well, requiring another huge delta-v to compensate if you want to avoid a crash-landing - a trip alone (not even landing) to Mercury requires more rocket fuel than to escape the solar system [wikipedia.org]. Solar-sails you say? Heck, how long can one afford to keep a maned space vehicle in a radiation 5-10 times more virulent than on Earth orbit. Bigger shields you say? Errr.... more rocket fuel to escape the Earth gravitation, I ask?
Heck, even if I would be to accept the idea of Mercury being more inviting, I wonder if we currently afford to give course to the invitation. Cost per kilogram of dead matter transported to:
1. the surface of Mars - US$309,000 [wikipedia.org]
2. a fly-by followed by orbiting Mercury (but not landing on it) - US$878,000 [nasa.gov] (Messenger mission cost/spacecraft mass).
BTW - the orbital insertion of the Messenger spacecraft around Mercury is expected in about 8 days from now (on March 17, 2011 after 6.5 years from its launch) - fingers crossed.
Re:Develop spacefaring technology first (Score:4, Interesting)
The problem with Mars is that pressure suits would have to use a lot of energy keeping their occupants warm.
No. Keep in mind that the occupants even when resting are 75 W heaters. Keeping the occupants cool is the real problem.
Re:Develop spacefaring technology first (Score:3, Interesting)
Although the defense spending is huge, it's still less than that for health care.
I'd far rather see a country spent more money on healthcare than on killing people. If the US Government really wants to save money, they should build less aircraft carriers - the incoming Gerald R. Ford class aircraft carrier, will cost $14 billion including research and development, and the actual cost of the carrier itself would be $9 billion each [strategypage.com] - nearly $100 billion in total for a like-for-like replacement of the eleven Nimitz and Enterprise class carriers in active service.
By comparison, the UK spends two and a half times [wikipedia.org] as much on Health as it does on Defence.