How long to travel to Pluto?

Queen Yinin said:

How far out is Pluto? Would an Earth ship (with todays technology) have even passed Pluto by then? Have I accidentally made that species live on Neptune?

So my question is:
Using today's technology, how long would it take a manned flight to reach Pluto?

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Er...this might be of interest.

Sage said:

So that was 9.5 years for an unmanned flight to Pluto

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It seems like such a short time to travel that far!

It would depend on the relative positions of the planets. I think the 9.5 years for the unmanned thing wa due in part to convenient locations. Too many variables. The guesses are all over the place.

Queen Yinin said:

I can't find anything in there about a manned flight.

I know it's not something anyone is seriously, I just want to know if I should be thinking in decades or centuries. Surely there's a rough estimate somewhere?

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It's SF, so you're not really bound by actual, you know, reality.

That said, some things to consider if you're not going totally in a Star Trek direction:

* More acceleration equals shorter time to arrive.

* Powered acceleration uses fuel. The more acceleration, the more fuel needed.

* Gravity "slingshots" off the sun or gas giants like Jupiter let you cheat and gain extra acceleration without extra fuel.

* Absent some hand-wavium solution, space travel exposes passengers to radiation. So the longer the flight, the more radiation they soak up.

* Absent some form of suspended animation, and/or stupendously efficient recycling, the longer the flight, the more supplies (food, water, air) are needed.

* Supplies (and fuel!) have mass, so at some point you're spending a lot of fuel to move that mass, as opposed to your passengers.

* Absent some hand-wavium solution like artificial gravity, prolonged weightlessness has serious bad side effects on the human body.

As for "how long", this is SF, so it really depends on how long your plot wants it to be!

Centuries? Pluto isn't orbiting another star, so no, probably not that.

Decades? If you're going to make it take decades, you need to address the supplies & radiation & weightlessness problems.

Multiple years? Same concern as decades.

Months? Possible, but you'll need a lot of acceleration. Doesn't need to be crushing, multiple gravities. A steady, small acceleration for a long time adds up. Google for online constant acceleration calculators to let you figure out how far you'd get if you could do (say) a tenth of a G for a month. I think the answer will surprise you. Don't forget that you need to stop accelerating when you're halfway to Pluto, so you can turn around and decelerate.

Personally, I think your best bet is to say it would take months. You still need to worry about All The Things: Fuel, supplies, radiation, weightlessness, but it's probably plausible half a century from now. And you don't need to freeze people to do it. ;-)

Fifteen years would be too long, because of the supplies necessary, even if there were things being grown. One place I saw suggested that a nuclear powered ship could do it in two or three years. That would make it possible. If it were going to take maore than three years, or so, then suspended animation would be a very good idea.

Queen Yinin said:

Thanks

I'm not actually explaining that much about the ships. The MC does ask but they don't explain it to her - she doesn't have necessary education to understand how earth rockets work, let alone SF ships...

They don't actually visit Pluto either, I just wanted to make sure I had my distances/travel times sorted out. I wanted them to be outside the system, so I needed to make sure the comparison to Earth ships is correct.

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If you're not claiming your ships are based on anything close to real technology today, then make the passage take what you want it to take. I wouldn't make it take hours, but I'd make it take less than many months. Constant acceleration adds up. If you could do constant 1 G, you'd get really far, really fast.

King Neptune said:

Fifteen years would be too long, because of the supplies necessary, even if there were things being grown. One place I saw suggested that a nuclear powered ship could do it in two or three years. That would make it possible. If it were going to take maore than three years, or so, then suspended animation would be a very good idea.

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Pretty sure some SWAG figures I read a few months back would get you there much faster than 2-3 years, if you could maintain a constant, even lowish acceleration? There are online calculators for this sort of thing. Have a good one bookmarked at home (am at work now).

At greatest distance, 7.5 billion km, at 1g it would take 30 days. At 0.1 g it would take 94 days.

Queen Yinin said:

http://www.astronomycafe.net/qadir/BackTo343.html

That one suggest 15 years, which I've been getting a lot, but I'm not sure how reputable that guess is. It puts Mars as less than a year away for a manned flight, which seems awfully short.

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You need to recognize some astro-planetary things about our solar system and Earth's place in it. Mars orbits next outside the Earth orbit, and takes about 1.7 Earth years to complete one orbit. That means the distance from Earth to Mars varies quite a lot, and the position of the two planets in their orbits matters a great deal when launching space probes from Earth to Mars.

Pluto, on the other hand, is so far away that it has only completed about 1/3 of one orbit since its discovery in 1930. It's distance from Earth, proportionally, doesn't vary all that much.

The New Horizons probe was about the size of a Volkswagen Beetle*. A spacecraft carrying humans obviously would need to be much, much larger, especially considering the vast amount of material (food, water, oxygen, fuel) needed for a decade or more of life-support. And that's just to get there. Getting back would take at least as much time, and if you postulate supporting humans out there for any length of time . . . . well, you get the picture.

Now, all that postulates a propulsion system similar to the technology we currently have. You're writing SF, so you have a lot of options for speculative technology.

As for "living on" Pluto, seems extremely unlikely. The place is so monstrously cold that it has nitrogen snow and ice on the surface. And very little atmosphere. It's dinky, smaller than our moon. And it receives, for all human purposes, essentially zero warmth from the sun.

As for "living on" Neptune, there is no "on" to live on on Neptune, nor for any of the other three gas giants in the system.

caw

So...is the other guy's home world orbiting a star or not? Because I would assume it's orbiting a star, and if that's the case, then you need to be thinking in terms of distances much bigger than the orbit of Pluto.

The closest star to our sun is about 5,500 times farther away than Pluto.

Queen Yinin said:

http://www.astronomycafe.net/qadir/BackTo343.html

That one suggest 15 years, which I've been getting a lot, but I'm not sure how reputable that guess is. It puts Mars as less than a year away for a manned flight, which seems awfully short.

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It depends on where Mars is relative to Earth in their orbital journeys. That sounds about right for current technology at an optimal launch time. Space agencies choose to launch their missions in windows that minimize travel time. For crafts being sent to the outer solar system, they also try to take advantage of gravity "boosts" to the craft's acceleration from other planets. Not sure if they were able to do this with the pluto flyby or not.

I don't see why a manned (and in the words of the late Carl Sagan, "and wooomand") mission would take longer than an unmanned one. We'd probably work even harder to make sure everything lined up perfectly if we were putting people on the ship. And it's possible that the future will see the invention of some kind of propulsion that will allow the ship to accelerate to a higher speed after launch (a larger, heavier craft that launches from space instead of the ground would also have room, possibly, for engines of some kind).

Roxxsmom said:

We'd probably work even harder to make sure everything lined up perfectly if we were putting people on the ship.

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When you're talking about the outer planets, "working even harder to make sure everything lined up perfectly" isn't really an option. The closest gas giant, Big Papa Jupiter, completes a solar orbit only once every twelve years. Saturn once every 27, as i recall. Uranus and Neptune take even longer. Back in the 1970s we had an unusually favorable alignment that permitted the Voyager probes to visit all four gas giants in succession, an alignment that won't be duplicated for centuries.

And, yes, you could perhaps launch a larger ship from orbit, rather than from the ground, but you still have to get the damn thing up there, along with all its requisite supplies and fuel.

caw

blacbird said:

When you're talking about the outer planets, "working even harder to make sure everything lined up perfectly" isn't really an option. The closest gas giant, Big Papa Jupiter, completes a solar orbit only once every twelve years. Saturn once every 27, as i recall. Uranus and Neptune take even longer. Back in the 1970s we had an unusually favorable alignment that permitted the Voyager probes to visit all four gas giants in succession, an alignment that won't be duplicated for centuries.

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True. I was thinking of Mars. With Pluto, you're right. It takes centuries for it to go around the sun.

And, yes, you could perhaps launch a larger ship from orbit, rather than from the ground, but you still have to get the damn thing up there, along with all its requisite supplies and fuel.

caw

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They could bring the ship components up in pieces and assemble them in space.

But for something really large, I'm imagining a futuristic society that builds the ships in orbit, maybe, and mines in space for many of the resources, and has permanent space stations in orbit--maybe even bases on the moon.

Queen Yinin said:

Yes his planrt orbits a star. But as long as its outside our system I dont mind it being a fictional star.

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That's fine, but just keep in mind that for it to be believable as a fictional star, it needs to be somewhat farther away than the closest star to us (Alpha Centauri) or it would be famous for being the closest star to us.

I guess what I'm trying to say is I think you should be more concerned about the time-of-flight that the character quotes being greater than what's required to get you to Alpha Centauri, rather than greater than the time-of-flight required to get you to Pluto.

Your question betrays a lack of research and basic understanding of the subject matter that will likely offend your reader.

You need to decide where your alien world is, relative to us, and how fast your star ships go. It's entirely up to you.

You don't need to be an astrophysicist to write this stuff but the planets are taught in primary school.

A decade at current speeds will get you to Pluto, but a millenia won't see you clear of this star system and the varied bodies orbiting the sun.

Another life supporting world is likely a long long way off. Far enough that a realistic speed won't work and you'll have to make one up.

Also consider that interstellar distances are measured in light years. The distance light travels in a year, so if you place your fictional world a thousand light years away, it will take a thousand years at light speed to travel that distance, but as a passenger, you'll be there before your coffee is cold enough to drink because of the effects of relativity.

It's a big area with mind blowing numbers, but not so obscure or complicated that your readers won't catch you out if you don't get the basics right.

Multiply the time it takes to get to Pluto by about 10,000 and you get to the amount of time it takes to get to the nearest star (aside from the sun, our own).

Space is really BIG, and things are really FAR AWAY.

And, for us here in this backwater arm of a barred spiral galaxy, that's probably a good thing.

caw