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Lifting the Veil On Pluto's Atmosphere
New submitter Pedro Braganca sends an update on the New Horizons mission to Pluto, now less than four days to closest approach. While we're waiting, NASA has published the best images of Pluto and Charon yet seen. We're starting to be able to make out surface details: A high-contrast array of bright and dark features covers Pluto's surface, while on Charon, only a dark polar region interrupts a generally more uniform light gray terrain. The reddish materials that color Pluto are absent on Charon. Pluto has a significant atmosphere; Charon does not. On Pluto, exotic ices like frozen nitrogen, methane, and carbon monoxide have been found, while Charon's surface is made of frozen water and ammonia compounds. The interior of Pluto is mostly rock, while Charon contains equal measures of rock and water ice.
A countdown to closest approach is present on the New Horizons mission page, as well as the raw image feed.
There is little point in commenting on this stuff for the next few days. Just enjoy. Pluto is getting very big in New Horizon's field of view. The book on Pluto will be rewritten every few hours now. Strange to comment on the atmosphere which we cannot see, when terra incognita lies before us.
Heliocentric velocities don't count. I should have said this:
https://en.wikipedia.org/wiki/New_Horizons
New Horizons was launched on January 19, 2006, from Cape Canaveral, directly into an Earth-and-solar-escape trajectory with an Earth-relative speed of about 16.26 kilometers per second (58,536 km/h; 36,373 mph); it set the record for the highest launch speed of a human-made object from Earth.
New Horizons was launched on January 19, 2006, from Cape Canaveral, directly into an Earth-and-solar-escape trajectory with an Earth-relative speed of about 16.26 kilometers per second (58,536 km/h; 36,373 mph); it set the record for the highest launch speed of a human-made object from Earth.
Still probably not correct. I refer you to the manhole cover over the Pascal-B nuclear test. Basically we unintentionally (maybe?) made a nuclear powered potato canon. (which is AWESOME) The manhole cover was estimated to have been launched at 41,000mph - possibly being vaporized in the process.
The delta v relative to Pluto is 11 km/s, which is not a whole lot in and of itself.
On the contrary, 11 km/s is huge! The Space Shuttle Main Engines, one of our most efficient rocket engines, has an Isp of 4.436 km/s. By the rocket equation this means that, to change velocity by 11 km/s using this engine, a spacecraft would need a ratio of wet mass to dry mass of exp(11/4.436) = 11.9. In other words, to stop the New Horizons probe at Pluto, we'd need to have sent along an extra 10.9 times its mass in fuel. And that's ignoring the mass of the engine and tankage, which makes things worse.
Fuel boil-off, as you mentioned, is an additional problem: it means we couldn't use the liquid-hydrogen/liquid-oxygen propellant used by the SSMEs, but some more stable (and less efficient) propellant, which further increase the required fuel mass.
By the way, doing a rough comparison: New Horizons was launched on an Atlas V 551, which has a capacity of 19t to LEO. To send the probe plus 10.9 times its mass in fuel would therefore take an equivalent capacity of ~11.9*19 = 226t to LEO. The Saturn V, the most powerful launcher ever made, had a capacity of 118t to LEO. So you'd need two Saturn V launches, rendesvousing in orbit, to get a spacecraft with enough fuel to fly to Pluto and stop there. (Probably 3-4 launches, when you consider the other problems described above.)
Another option is to use an ion engine, which has an extremely high specific impulse, so it requires less fuel. But that has an additional problem: ion engines require lots of power, and solar panels are useless out at Pluto, so you need a big, heavy nuclear reactor.