[Need some help] Simulation on mission to Alpha Centauri

[NERVAfan]

I thought Orion drive (nuclear pulse propulsion) was up to the job of a quick-ish interstellar trip. It would still require a big ship, probably needing something like lunar or asteroid mining to make costs tolerable, but use a proven method of nuclear fusion rather than something still in the distant future.

Daedalus is nuclear pulse propulsion too, just a version not involving actual nuclear bombs. (although to be fair, a real Orion would use nuclear devices optimized for propulsion. It's not REALLY a matter of grabbing nuclear warheads off a military base and pitching them out the back of a spaceship).

I do think nuclear pulse is the best interstellar technology, as it allows really big ships and thus heavy shielding - I'm skeptical of the light laser/microwave/whatever beamed sail craft that are proposed surviving interstellar dust collisions.

EDIT: best that doesn't require any major breakthroughs, that is. Antimatter rockets or Bussard ramjets or FTL drives or whatever would be better.

[magnemoe]

Daedalus is nuclear pulse propulsion too, just a version not involving actual nuclear bombs. (although to be fair, a real Orion would use nuclear devices optimized for propulsion. It's not REALLY a matter of grabbing nuclear warheads off a military base and pitching them out the back of a spaceship).

I do think nuclear pulse is the best interstellar technology, as it allows really big ships and thus heavy shielding - I'm skeptical of the light laser/microwave/whatever beamed sail craft that are proposed surviving interstellar dust collisions.

EDIT: best that doesn't require any major breakthroughs, that is. Antimatter rockets or Bussard ramjets or FTL drives or whatever would be better.

Daedalus and longshot uses pulsed fusion, benefit is that they don't use bombs but external devices for triggering the fusion this gives better isp as you don't need the heavy bomb around the fuel.

Orion is not really practical for interstellar ships. isp is too low making it too slow or too big to be practical.

[magnemoe]

I was just about to also suggest Project Longshot as a reference.

It is probably one of the more realistic proposals for an interstellar mission to the Centauri system.

PROJECT LONGSHOT:

http://en.wikisource.org/wiki/Project_Longshot

Thank, it was interesting. One question why will they trust all the way to turnover? it makes very little sense as the later part of the burn would hardly give any time saving.

So bad that the last fuel burned would be better dumped at start as it reduces acceleration

Had been smarter with an more powerful engine and less fuel who let you do the burn during the first 25% of the trip, this would save fuel making the ship lighter.

Burning to turnover only makes sense if you don't use reaction mass.

[Hattivat]

snip

Sweet kraken, this is getting out of hand Ok, so I'm not that much into how telescopes are working and might not have picked the best words to express myself, my bad. In any case, what I meant was something akin to the Kepler telescope - it sends 'data' on planets, not images of them. In fact AFAIK that's what most of our exoplanetary observations are like at the moment - we have quite a lot of data on extrasolar planets that we have yet to produce an image of - so I simply extrapolated that into the future.

Besides, if there is a hard limit on the resolution we can obtain from telescopes that prohibits us from observing exoplanets, then Claudio Maccone (apparently a well-respected Italian astronomer) is seemingly unaware of it, because in his "Deep Space Flight Communications" book he calculates the spatial resolution theoretically attainable by a 12-meter antenna beyond 550 AU pointed at alpha centauri to be between 81 km and 1248 km, depending on targeted frequency. And that's with a radio telescope, theoretical resolutions I've seen calculated for visible light elsewhere are simply mind-boggling, ranging from a few dozen meters to about a kilometer, depending on the source (with a correspondingly massive increase in required receiver size and positional precision). So it would seem it is indeed possible to make direct visual observations of exoplanets without leaving the vicinity of our solar system, making the whole discussion on "data vs images" pointless.

@Metaphor, quoting from the same book as above:

And the very important astronautical consequence of this fact for the FOCAL mission is that it is not necessary to stop the craft at 550 AU. It can go on to almost any distance beyond and focus as well or better. In fact, the farther it goes beyond 550 AU the less distorted the radio waves by the Sun Corona fluctuations.

@magnemoe: My guess would be that the ability of the spacecraft to radiate the produced heat is limiting the rate at which it can burn its fuel. The same problem that Orion has - with perfect radiators it could reach Alpha Centauri in 130 years, but realistically it would take thousands of years due to breaks necessary to cool the pusher plate.

[kurja]

Sweet kraken, this is getting out of hand Ok, so I'm not that much into how telescopes are working and might not have picked the best words to express myself, my bad. In any case, what I meant was something akin to the Kepler telescope - it sends 'data' on planets, not images of them.

or quite literally, in the hand?

Even the Kepler space telescope is basically a big camera. Data about the exoplanets is derived of the images it produces, not the other way round.

[magnemoe]

Sweet kraken, this is getting out of hand Ok, so I'm not that much into how telescopes are working and might not have picked the best words to express myself, my bad. In any case, what I meant was something akin to the Kepler telescope - it sends 'data' on planets, not images of them. In fact AFAIK that's what most of our exoplanetary observations are like at the moment - we have quite a lot of data on extrasolar planets that we have yet to produce an image of - so I simply extrapolated that into the future.

Besides, if there is a hard limit on the resolution we can obtain from telescopes that prohibits us from observing exoplanets, then Claudio Maccone (apparently a well-respected Italian astronomer) is seemingly unaware of it, because in his "Deep Space Flight Communications" book he calculates the spatial resolution theoretically attainable by a 12-meter antenna beyond 550 AU pointed at alpha centauri to be between 81 km and 1248 km, depending on targeted frequency. And that's with a radio telescope, theoretical resolutions I've seen calculated for visible light elsewhere are simply mind-boggling, ranging from a few dozen meters to about a kilometer, depending on the source (with a correspondingly massive increase in required receiver size and positional precision). So it would seem it is indeed possible to make direct visual observations of exoplanets without leaving the vicinity of our solar system, making the whole discussion on "data vs images" pointless.

@Metaphor, quoting from the same book as above:

@magnemoe: My guess would be that the ability of the spacecraft to radiate the produced heat is limiting the rate at which it can burn its fuel. The same problem that Orion has - with perfect radiators it could reach Alpha Centauri in 130 years, but realistically it would take thousands of years due to breaks necessary to cool the pusher plate.

Yes, I'm aware of the heat radiation issue, however even carrying the fuel for the last part of the burn is an waste as you accelerate slower in the start. replacing part of the fuel with an more powerful engine and more radiators would speed you up even more. not saying doing the burn in 1-2 years but more like 20-25 as you want to spend most of your time idle.

And sound to me like an telescope at 550 AU would be an natural scouting mission to an interstellar mission to check out the target. And its litle reason to send one who don't involve lading probes . You detect an interesting planet by other means and send an telescope to 550 AU in the other direction to get a better view.

[Hattivat]

or quite literally, in the hand?

I'm afraid I don't get the reference here.

Even the Kepler space telescope is basically a big camera. Data about the exoplanets is derived of the images it produces, not the other way round.

Yes, I am aware that it is a giant camera that derives data from images. Are you aware that it is deriving data about planets from images that are not images of planets? Great, now you know what I meant (it's easier to obtain data on an exoplanet than a picture of it) and we can move on.

@magnemoe: Yes, it also seems wasteful to me. This article suggests that the Longshot study is substantially flawed, which would also explain why NASA still seems to regard Daedalus as the baseline study, even though it's older.

And yeah, the "detect by other means => observe from beyond 550 AU => send a probe" order of operations also seems the most reasonable to me.

Edited September 29, 2014 by Hattivat

[-Velocity-]

I was catching up on this whole thread at once, and you stopped me cold here. Been staring at the ceiling for several minutes, and I think you're right. I can't come up with any known or plausible form of energy storage that'll last over 20k years. Not even one that'd work on Earth in a controlled environment, much less in space with ionizing radiation and temps near absolute zero.

A most interesting puzzle!

Nuclear reactors would work, especially if fusion became feasible. Uranium-235 has a half life of several hundred million years, so even a fission reactor could feasibly work- you wouldn't run it continuously for 20k years. You'd run it in spurts. Start it up, run diagnostics, see if anything on the ship needed repair, if so, power up the robot wardens, have them go fix whatever needed fixing, etc., then go into hibernation mode again.

Edited September 29, 2014 by |Velocity|

[kurja]

I'm afraid I don't get the reference here.

Last link in my post with the pictures I thought you were referring to that yourself...

Yes, I am aware that it is a giant camera that derives data from images. Are you aware that it is deriving data about planets from images that are not images of planets? Great, now you know what I meant (it's easier to obtain data on an exoplanet than a picture of it) and we can move on.

You still need the image (link) in the first place, to get that data out of it.. Afaik KST has the ability to perform some initial analysis on it's images so it can only transmit relevant stuff instead of everything but it's still definitely transmitting images, not some mythical 'data' that somehow isn't an image anymore. Since you already knew that, I'm at a loss to why you don't believe resolution affects what data can be produced with a telescope. But sure, we can move on.

[Hattivat]

Ah, yes, I was, partially (I also meant it in the more conventional sense that this off-topic is needlessly developing into a full-sized discussion), I just thought that "in the hand" might be an idiom or some other conventional expression that I'm not familiar with (English is not my first language).

I never said that resolution does not affect what data can be produced with a telescope. I only meant that "maximum resolution is too low to directly image a planet" != "we can't learn more about a planet", just as "KST does not produce images of planets" != "KST does not provide data about planets". Read it again:

What I posit is that a space telescope from anno 28 000 will be able to detect the atmospheric composition, size, shape and even true color of planets in the Alpha Centauri system in much better detail than a tiny probe from anno 2014 flying millions or even billions of kilometers away from these planets, even if it may never be able to produce an actual picture of them for use in screensavers.

Isn't it clear that I'm talking about something like an upgraded version of KST here? Data from KST and other telescopes is already fueling pretty detailed speculation on the composition, size and other characteristics of plnaets that we have never "seen". I simply assumed that this can be improved upon in the 26 000 years between now and the arrival of OP's probe.

And besides, as I pointed out in one of my posts above, it appears that the maximum possible resolution is in fact high enough to directly image a planet under certain conditions, so the whole discussion is moot.

[kurja]

Isn't it clear that I'm talking about something like an upgraded version of KST here? Data from KST and other telescopes is already fueling pretty detailed speculation on the composition, size and other characteristics of plnaets that we have never "seen". I simply assumed that this can be improved upon in the 26 000 years between now and the arrival of OP's probe.

And besides, as I pointed out in one of my posts above, it appears that the maximum possible resolution is in fact high enough to directly image a planet under certain conditions, so the whole discussion is moot.

Fair enough. However in the long run I'd expect more advances in how data from space telescopes is reduced and analyzed, to fuel new discoveries, than any massive advance in telescope technology itself.

[NERVAfan]

Daedalus and longshot uses pulsed fusion, benefit is that they don't use bombs but external devices for triggering the fusion this gives better isp as you don't need the heavy bomb around the fuel.

Orion is not really practical for interstellar ships. isp is too low making it too slow or too big to be practical.

I thought the original Orion people suggested that an advanced version could get to several percent of lightspeed?

There's also the Robert Zubrin "nuclear-salt-water-rocket" concept, which IIRC supposedly could be optimized to a few percent of lightspeed as well, but I don't know if anyone else has ever really studied that.

@magnemoe: My guess would be that the ability of the spacecraft to radiate the produced heat is limiting the rate at which it can burn its fuel. The same problem that Orion has - with perfect radiators it could reach Alpha Centauri in 130 years, but realistically it would take thousands of years due to breaks necessary to cool the pusher plate.

IIRC the Orion people talked about some kind of ablative coating that burned away to protect the pusher plate itself. I don't know if it's enough though...

[StuntMax]

By the time it arrives in the alpha centauri system we'll have space bases there to watch it fly past.

"Far Centaurus", A.E. Van Vogt, Astounding Science Fiction, 1948

[magnemoe]

I thought the original Orion people suggested that an advanced version could get to several percent of lightspeed?

There's also the Robert Zubrin "nuclear-salt-water-rocket" concept, which IIRC supposedly could be optimized to a few percent of lightspeed as well, but I don't know if anyone else has ever really studied that.

IIRC the Orion people talked about some kind of ablative coating that burned away to protect the pusher plate itself. I don't know if it's enough though...

For an orion bigger is better, mostly as you can go for fusion bombs who has more power / weight ratio, many ways to protect the pusher plate, one is the bomb itself, an magnetic field, ablative coating or spray inn oil or something over it while launching the bomb.

Note that Orion would make an good first stage, high twr but low isp for interstelar.

Nuclear salt water is far more kerbal than orion, it has some problems with control or the reaction, my guess is that it would be smarter to inject the plutonium separately, makes me wonder if it could be run on just plutonium, another idea would be an orion where you accelerated plutonium slugs with an coilgun towards each other, yes you would need something else in the slugs, also an neutron source,

[corous]

I was just about to also suggest Project Longshot as a reference.

It is probably one of the more realistic proposals for an interstellar mission to the Centauri system.

PROJECT LONGSHOT:

http://en.wikisource.org/wiki/Project_Longshot

A most interesting find, sir. Thank you.

[Frozen_Heart]

So why are we insisting on chemical only? Surely Nuclear, Ion or Vasmir would be a better solution and all are achievable with modern day tech.

[magnemoe]

So why are we insisting on chemical only? Surely Nuclear, Ion or Vasmir would be a better solution and all are achievable with modern day tech.

Original specifications and no neither nuclear, ion or vasmir would work better, reducing traveling time to 5000 year would not be very useful.