How difficult is interstellar travel?

[ConspiRaider]

Hollowed out planetoid or asteroid. There's your spaceship. It's the only way - the ONLY way - we'll ever get to the stars.

Can't exceed the speed of light. Impossible. An object - such as you or me - not already moving at the speed of light cannot even be accelerated to the speed of light. Let alone "breaking" the light speed barrier. That's fantasy.

A mobile planetoid or asteroid is what will do the trick. A self-sustaining, self-restorative environment that mimics Earthlike living conditions as much as possible.

My proposal is this, and I think we should begin work on it immediately. We bring - via landed propulsion - an asteroid into Earth orbit. Something we can work with. This will be our manned solar-system travel method. Not rocket ships for a small crew or anything like that. Too time-consuming, not practical in the long run. Let's bench test the Holy Grail of interstellar travel via interplanetary travel within our own solar system first. That gets all the kinks out of the way.

There are enormous problems. Propulsion. Shielding from cosmic rays. Creating a breathable atmosphere. Mimicry of 1g gravity, and atmospheric pressure of 14.7 pounds per square inch. A light source to mimic sunlight. And so forth. In other words, a miniature Earth, in which people can live, stretch their legs, and walk around the joint without environmental suits. Without losing bone mass due to lack of gravity.

It should be started now. It won't be long before the Earth itself will no longer provide a palette for the restless, adventurous spirit of our species. How much longer can virtual reality and video games and pretend this or that satisfy our quest for real pioneering? We have to expand outward. Have to. So let's just acknowledge that and get to work.

If I was heading NASA, this is the agenda I'd be pushing.

 

[RecoveringYuppy]

@Paulhoff and Huntsman

I hope you two noticed the first sentence of my post.

 

[Paulhoff]

I'm kind of baffled by people who think the power requirements seem impossible.

Nobody said that it was impossible, but it certainly isn’t just using some bombs and we're off to the stars.

Paul

 

[RecoveringYuppy]

Well, at least one article has been cited that says it's effectively impossible, but, no, you didn't say it was impossible. And I just want to be clear that I didn't say it was just using some bombs.

My point was simply that power and energy requirements cited by that article as outrageous are actually obtainable now. 1.5 GW is not all that big a deal. Our largest boosters are in the neighorhood of terrawatts. And we're already experimenting with long term ion style engines in the megawatt range. The power and energy levels cited in that article are quite manageable right now.

But here's another objection that baffles me, and it's come up more than once. I'll quote Huntsman's version of it.

We can't give commands with a four year plus time lag...the craft has to find anything interesting on it's own, manuever to observe it, and know what to report wihtout intervention. It'll have to make judgements on what to study...we wouldn't want to go to Alpha Centauri, say, and study the star for a year, to find out there's a very interesting planet there that we can't tell the spacecraft to look at.

I find it hard to believe that we won't have the system pretty well mapped out in or before the decades it takes to get there. We're working on optical systems that could detect planets right now. And if we were actually planning a mission to Rigil Kent we could map it by radar in the time it would take the probe to get there.

A viable first probe might even be a simple radar study of the system that gets more and more detail the closer it gets. It would have payback even if it didn't make it all the way or was just a flyby.

 

[ecacofonix]

The topic - while largely academic in nature - is quite interesting though...

Of course, as some pointed out, the big question is: what is the point? What are we trying to figure out from AC by being there that we cannot figure out using our powerful telescopes et al...

But travel at even a fraction of the speed of light? This, I think, will be the real issue...especially we are still in the period of talking of Machs - which is not even a poor cousin of the speed of light!

I doubt travel at anywhere close to speed of light will happen in the next 1000 years...well, the good thing of course is that if it happens I won't be around for someone to tell me I was wrong

NS @ Trazoo

 

[Corsair 115]

There have been many stories with similar situations.

The first ones that comes to mind is Star Trek (TOS) episode "Space Seed" where the pre-warp starship Botany Bay carrying astronauts from early 21st century Earth is intercepted by Enterprise.
Similar: Star Trek (TNG) episode "The Neutral Zone".

Just to return to this point about previous stories, I found the example I had read. It was indeed written by A.E. van Vogt, a short story entitled Far Centaurus. It appeared in a book containing a collection of van Vogt short stories.

 

[rockoon]

This would help make small advances but would rely 100 % on resources and equipment being brought up from Earth.

Until we can make planets habitable which are completely self sufficient, there won` t be any further human expansion in our galaxy.

Why do people always assume that we will be living on planets?

Yes, some of us will. But it is ridiculous to think that the majority of humans will be.

Our population will overflow the supportive capacity of the Earth. If you think that Mars is the answer, you would be wrong. We will overflow the supportive capacity of that planet too. The various moons arent an answer either. We will overflow their capacities as well.

We will spread out through the universe like a cancer. Overflowing the capacity of every planet or moon we encounter. The vast majority of humans will live between planets, on man made crafts built for that purpose, harvesting needed materials from wherever it is reasonable to do so (asteroids, comets, nebula, space dust, ... and yes, planets and moons too)

 

[BlackKat]

Why do people always assume that we will be living on planets?

Yes, some of us will. But it is ridiculous to think that the majority of humans will be.

Our population will overflow the supportive capacity of the Earth. If you think that Mars is the answer, you would be wrong. We will overflow the supportive capacity of that planet too. The various moons arent an answer either. We will overflow their capacities as well.

We will spread out through the universe like a cancer. Overflowing the capacity of every planet or moon we encounter. The vast majority of humans will live between planets, on man made crafts built for that purpose, harvesting needed materials from wherever it is reasonable to do so (asteroids, comets, nebula, space dust, ... and yes, planets and moons too)

Planets are significantly better at making meat and produce though. At least at this point, there is a pretty low cap on the yield of hydroponics. And could you imagine how taxing cows would be on a life support system?

Of course the good news would be mucking out the barn could be done largely by decompression.

I imagine that whenever possible planetary life is always going to be more desirable than life in an orbital colony. Things on this planet (or future ones) will have to be pretty screwed up to get significant numbers of people to try a new way of life.

 

[rockoon]

I imagine that whenever possible planetary life is always going to be more desirable than life in an orbital colony. Things on this planet (or future ones) will have to be pretty screwed up to get significant numbers of people to try a new way of life.

This is the biased view of an earther.

 

[Jimbo07]

Why do people always assume that we will be living on planets?

Can you think of a better place to live?

Yes, some of us will. But it is ridiculous to think that the majority of humans will be.

And even more ridiculous to think that the majority won't be!

Our population will overflow the supportive capacity of the Earth.

When will that be?

If you think that Mars is the answer, you would be wrong. We will overflow the supportive capacity of that planet too. The various moons arent an answer either. We will overflow their capacities as well.

We're not a bacteria with unlimited resources available, but even if, in the strangest of circumstances something like this would happen... it won't be for a very long time.

We will spread out through the universe like a cancer. Overflowing the capacity of every planet or moon we encounter. The vast majority of humans will live between planets, on man made crafts built for that purpose,

Planets are the biggest spaceships going. I can't see the majority of humans living on space vehicles while there are planets around.

harvesting needed materials from wherever it is reasonable to do so (asteroids, comets, nebula, space dust, ... and yes, planets and moons too)

Why not just live on the planets and use the resources there? This post is strange. It's sort-of posits a sci-fi scenario where human population has grown so dense that we're like a fungus on the surface of planets and are popping out into the voids between. You'd have to do a lot of work to turn something like this into a good (or even plausible) sci-fi story.

 

[RecoveringYuppy]

Seems to me that if we can colonize space at all that it will have to become the primary home of humans. The billion to one energy/resource advantage seems overwhelming to me.

Objections based on "hydroponics" seem particularly myopic.

 

[geni]

To points raised by others:
As to the time frame, that depends (to a degree). I think we're more limited by the maximum possible lenght of a political reign than by lifespan. Few Presidents would go for anything that won't even begin to show results until long after they're out of office. I'd imagine that holds true, to a greater or lesser extent, for other countries as well.

The Jubilee River would probably qualify. Simply getting something that size started would probably rank as enough of an atchivement to be worthwhile in that respect.

 

[geni]

Our population will overflow the supportive capacity of the Earth.

Doubtful. Currently it appears that conteraception pluss empowered women results in negative population growth.

 

[rockoon]

Can you think of a better place to live?

What is this whole "better" stuff?

Better for who?

Planets are the biggest spaceships going. I can't see the majority of humans living on space vehicles while there are planets around.

Most planets do not qualify for the "better" life you envision.

Venus is too hot, Mars is too cold, and lets not forget all the moons.

Living in climate controlled containers on these big gravity wells will be just like living in space, without any of the advantages of living outside of big gravity wells.

Why not just live on the planets and use the resources there?

First you have to make the planet livable. So there we are, living in a relatively small climate controlled container while the planet is terraformed.

Why exactly do we want to move to the planet again?

This post is strange. It's sort-of posits a sci-fi scenario where human population has grown so dense that we're like a fungus on the surface of planets and are popping out into the voids between. You'd have to do a lot of work to turn something like this into a good (or even plausible) sci-fi story.

Oh, I see.. you base your reasoning on sci-fi stories. Trantor and all that?

 

[CapelDodger]

Don't underestimate the speed of tech advance. Think of it this way; in 1900 we could not fly. Yet, by 1969 we landed a man on the moon. In just 69 years we went from no flight to landing on the moon.

70 years from now we could be living on the moons of Jupiter if the pace of tech advancement continues to exponentially accelerate.

Sticking with the analogy, in 80 years we might have been to the moons of Jupiter and be discussing whether it's worth going back.

 

[whiteyonthemoon]

To give a different perspective on those numbers, his power requirement works out to about 1.5 gigawatts when the energy is spread over the duration of the mission he is describing. A solar power stations based near the orbit of Mercury would need under a square kilometer to catch that energy.

Right, for a ridiculously small vessel without factoring in the relativistic contribution of weight increase, assuming 100% energy conversion (therefore we can't use a rocket or ion drive), and I think the article doesn't even factor in the energy needed to stop the vessel.

How long would it take to gather 1.5 gigawatts energy with the solar power station you propose?

And how can we mention gigawatts without suggesting that we might just want to invent a Mr. Fusion unit and use that?

 

[rockoon]

Right, for a ridiculously small vessel without factoring in the relativistic contribution of weight increase

You do not truely understand relativity.

The ships mass will appear constant from the ships perspective (well, it will actualy decrease as it expends its energy store)

There is never a point where you say "omg i'm heavier!" However outside observers might say "omg he is heavier!" - thats relativity.

How long would it take to gather 1.5 gigawatts energy with the solar power station you propose?

You do not truely understand energy and power units.

The Watt is a unit of power equal to 1 Joule per Second.

The Joule is a unit of energy.

So 1.5 gigawatts is 1.5 billion joules per second.

To put this in perspective, the typical lightbulb consumes 60 to 80 watts of power, or about 60 to 80 joules per second.

To answer your question, "1 second"

 

[Stitch]

To answer your title question, it is unbelievably difficult to do interstellar travel, no matter if it is slow or fast, using current technology.

To answer your question on the time it would take a ship capable of constant 1g acceleration to travel 4.3 lightyears and then come to a stop, it would take about 1 year to reach 90% of lightspeed, about 3 years of cruising, and about a year to stop. In total, somewhere around 6 years in total.

OK, colour me stupid, but why does the acceleration and deceleration have to be 1G, assuming G to be the force of gravity. Is this merely to generate a "synthetic" gravity for the people on board?

 

[rockoon]

OK, colour me stupid, but why does the acceleration and deceleration have to be 1G, assuming G to be the force of gravity. Is this merely to generate a "synthetic" gravity for the people on board?

Mainly, yes.

Also of note is that 2G doesnt get you there twice as fast (There are diminishing returns.)

While 1G happens to be the acceleration of choice, I suspect a somewhat larger value will be used assuming constant acceleration is practical.

Edited to add:

It may not be due to unavoidable factors, such as the velocity you are pushing through the interstellar medium (space dust, and space gravel) .. there may be some limit on the speed you can safely travel relative to this medium. 1 gram of rock traveling near the speed of light relative to you packs a pretty big punch.

 

[Stitch]

Mainly, yes.

Also of note is that 2G doesnt get you there twice as fast (There are diminishing returns.)

While 1G happens to be the acceleration of choice, I suspect a somewhat larger value will be used assuming constant acceleration is practical.

No I appreciate that, but just wondered on the 1G, I'd have thought, go for a big punch at the start and then ease back to IG, but thanks for answering the question!

Edited to add:

It may not be due to unavoidable factors, such as the velocity you are pushing through the interstellar medium (space dust, and space gravel) .. there may be some limit on the speed you can safely travel relative to this medium. 1 gram of rock traveling near the speed of light relative to you packs a pretty big punch.

1 gram of rock travelling at a couple of times the speed of sound packs a pretty big punch!