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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.
Charon is about 750 miles (1200 kilometers) across, about half the diameter of Pluto—making it the solar system’s largest moon relative to its planet.
Sounds like someone at NASA is still not over Pluto not being a planet. Let it go... let it go...
Those who do not learn from commit history are doomed to regress it.
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.
A Delta V wouldn't have anywhere near the energy needed to slow it down enough for orbit. Remember that the rocket engine and fuel would be traveling at the same speed as the probe, that's a tremendous amount of kinetic energy.
New Horizons is the fastest object ever launched.
No it is not. Not even close to the fastest object we've ever launched. That honor goes to the Helios-A and Helios-B probes which traveled about 70km/s. Much faster than the 16km/s of New Horizons.
Delta-V isn't a rocket. (You might be thinking of Saturn V.) Delta-V is change in velocity: in this case, how much the spacecraft would have to slow down in order to enter orbit instead of just flying past.
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. My understanding is that fuel boil-off during the 10 years of transit to Pluto makes it very difficult and expensive to bring along enough fuel for a retro burn to put a spacecraft into orbit around Pluto.
It would have been pretty awesome to have an obiter that could zip around Pluto and Charon and do observations. Maybe next time.
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.
He meant either a Delta IV or an Atlas V, the heaviest rockets available in the US today.
My bad; Tomhath was referring to either a Delta IV or an Atlas V and making two errors in the process, the OP was talking about delta-V as in speed change. Serves me right for answering before reading the complete thread.