Yet Another Pluto Mission Competition?

NASA Watch ^ | Keith Cowing

[Fitzcarraldo]

It would seem that the Administration did not like the action taken by the Senate last week when it restored funding for a mission to Pluto. Word has reached NASA Watch that an effort is underway whereby the New Horizons mission will be terminated and then recompeted.

According to sources Office of Space Science AA Ed Weiler discussed this topic in his staff meeting on Thursday. During the New Frontiers preposal conference on Tuesday, NASA went out of its way to reserve the option of starting all over again with a new solicitation.

One of the obvious effects of yet another delay in a mission to Pluto would be to further delay the launch date. It would likely take at least another year or so for the proposal development and evaluation process to conclude (well into 2003) with a final selection unlikely until early 2004. Delays in the launch date would likely necessitate additional propulsion costs since a gravitational assist maneuver at Jupiter would be missed.

[Fitzcarraldo]

Spend on the order of a billion $$$ to travel 3 billion miles and spend 10 minutes observing Pluto as the spacecraft flies by?

I say wait 20 years until we have the propulsion technology to go into orbit around Pluto and its moon, Charon.

I would rather spend $30 million to directly confirm ice at the lunar poles (the existence of which is now in doubt because bistatic radar measurements have been reinterpreted as not providing evidence of lunar ice).

[Fitzcarraldo]

bump

[traditionalist]

I say wait 20 years until we have the propulsion technology to go into orbit around Pluto and its moon, Charon.

I don't understand. We can put spacecraft into orbit around other planets. Why is Pluto different? Why can't present technology put something into orbit around, say Mars or Venus, but not Pluto? I understand Pluto is a lot further away, but I don't understand why the greater distance is relevent.

[KevinDavis]

I think a manned mission to Mars should be the priority. Not a mission to Pluto.

[LibWhacker]

Good question bump. We're accustomed to seeing flybys when the spacecraft has to visit several moons and planets, but in this case there is nothing beyond Pluto to visit. I wonder if orbiters are more costly than flybys?

[Great Wombat]

I have a guess as to why Pluto is harder to get an orbit for. It is a LOT further away than Jupiter and Saturn. It also has a much smaller mass (which naturally means its gravitational pull is very small also). It may be that since it is so very far away, the spacecraft must travel much faster to get there in a "reasonable amount of time". It will therefore need tremendous effort to get it to slow down enough to attain orbit, rather than fly by. Pluto's gravitational weakness will hamper the use of its gravity alone for this purpose. If I am not mistaken (and I may well be, I am out of the loop on scientific advances here in South America) we have never even orbited a craft around Uranus or Neptune, but did get some nifty shots of them with a Voyager fly by.

I think that it might still be worth doing even if we can only manage a fly-by type expedition--look at what the Voyagers let us see. Alternately, I doubt that it will really have to be 20 years before an orbiter is possible. If the US puts its money on a project and is allowed by its space budget to dedicate enough research to it, it could be much earlier. It took less than ten years to go from having every other rocket blow up on the launch pad to landing actual people on the moon.

[LibWhacker]

Speaking of orbiters, here's a free space flight simulator called Orbiter that I found while looking for an answer to traditionalist's question.

[reg45]

I propose Hillary as Mission Commander and Tom Daschle as Chief Photographer. Our money could not be better spent.

[Andy Ross]

The trajectory of a craft on its way towards a planet is drastically different to the trajectory of the planet itself. To go from the one to the other takes a great deal of effort.

When we're sending things to Jupiter and other massive bodies, we can take advantage of their own gravitational forces to alter the energy state of the spacecraft. With Pluto being so tiny: it's really little more than a big asteroid; its puny gravitational strength is not conducive to a good transition. It's not impossible, but it is very impractical, to orbit Pluto.

Personally, I'm not convinced by the desire to send a craft to Pluto. Very little is to be gained by investigating the outer planets. I'd much prefer to see missions much closer to home (lunar missions and Mars).

Andrew

[traditionalist]

Thanks for the explanation. I've need to bone up on my physics.

[magellan]

To put something in orbit around Pluto, you have to slow it down to orbital velocity. This means we would have to send the spacecraft to Pluto at a slow speed, and it would take 20 years to get there.

To get a spacecraft there in under 10 years, it has to go very fast. Therefore, it would take a large amount of fuel to slow it to orbital velocity. The weight of the fuel would cause the whole mission to cost more.

[mvpel]

Twenty years from now Pluto will have moved far enough away from the Sun that its tenuous atmosphere will have frozen out and snowed onto the surface, there to remain for another 120 years. Time is running out to observe Pluto's unique atmosphere, one of only five solid bodies in the known universe to have one.

The reason why it's so much more difficult to orbit Pluto is that you have to take along all the fuel you need to slow down enough to get into orbit, and in order to take that fuel, you have to push it up to tens of thousands of kilometers per hour, which takes more fuel at the outset. And the faster you go, the more fuel you need to slow down.

It's taking the Cassini probe, which is to go into orbit around Saturn in 2004 and which is travelling at 30,000 kilometers per hour with respect to the Sun, 7 years to get to Saturn even after it was launched on the most powerful booster available, the Titan IV.

Pluto is 4.47 billion kilometers away, versus Saturn's 1.47 billion kilometers, three times as far. Keeping the Galileo probe functional since its October 1989 launch and its 1995 arrival at Jupiter has been an ongoing struggle, one that is not likely to succeed much longer, and that's over the course of a mere 13 years.

It took from 1977 to 1989 for Voyager 2 to reach Neptune to fly past it at tens of thousands of kilometers per hour using a gravity assist opportunity that comes along only once in 176 years.

The upshot is that with current propulsion technology, going into orbit around Pluto would take decades, far beyond the expected lifetime of space-worthy systems, and thus miss the atmosphere. Here's the web page of the Pluto/Kupier Express Mission.

[magellan]

"I say wait 20 years until we have the propulsion technology to go into orbit around Pluto and its moon, Charon."

What make you think we will have better propulsion technology in 20 years? I has been 33 years since Apollo 11 went to the moon and we have mode only very minor improvments to space propulsion systems. Most of these improvements were made as part of the Space Shuttle system in the 1970's. In essence, space propulsion today is not any more sophisticated than space propulsion was in the late 1960s.

Time alone does not cause technogy to advance. An active effort is needed. From 1961 (Kennedy commits U.S. to the moon) to 1967 (first unmanned Saturn V launch) the U.S. advanced the state of the art on space propulsion. That would not have happened if not for the money or pressure of Project Apollo.

[traditionalist]

That was very informative. Thanks for posting.

[MainFrame65]

Pluto has the most eccentric (football-shaped) and inclined orbit of all of the planets. At the moment, it is actually CLOSER to the sun than Neptune, the next most distant planet in terms of average distance. This condition exists for about 40 years, or about 10% of its complete trip around the sun.

In addition, its current proximity to the orbital plane potentially allows a gravity-assisted path that could considerably shorten the travel time. This method has been used for other interplanetary missions several times in the past, with great success. The spacecraft is routed near one of the other planets, close enough that the planet attracts - and accelerates - it, cutting significant time off of the total time. Less time also means less exposure to failure.

These are not definitive arguments, but they are real.

[RightWhale]

The deal with Pluto is that is is now relatively close to the sun and in a few years will be farther away. Apparently there are volatiles that are now in the atmosphere but that will be frozen on the ground if they wait too long. To catch Pluto in its warmer state again means waiting 200 years if the miss this opportunity.

It doesn't matter a lot. Pluto might be the key to development in the outer solar system, but that is a ways off in time.

[catherine of alexandria]

Problem is, that we'd have to feed them. And give them air to breathe.

[LibKill]

I'm with you. Mars first. Pluto will still be there later on.

[HighWheeler]

Pluto crossed inside Neptune in 1979 and crossed back outside again in 1999. Due to the layout of their orbits, They will never collide. Look at this side view, it's pretty cool.

[RightWhale]

there is nothing beyond Pluto to visit.

Where have we heard something like that before? Going to sail off the end of the world are we?