Talk:Interstellar travel/Archive for 2007

Recent edits need work before merging

The following was recently added to the article. I took it out temporarily until some serious problems can be resolved.

The nearest star to the Sun is the triple system Alpha Centauri. Light radiating from that star takes more than 4.2 years to reach Earth.

A trip with the current standard spaceship, the Space Shuttle, which travels at 28500 km/u, would take 160,000 years.

First of all, what's a km/u? Standard units here would be km/s or fractions of c. Second, giving a speed for a spaceship is highly misleading, as they do not have top speeds. The exhaust velocity does give a practical order-of-magnitude upper limit if no special tricks (gravitational assist, planet-based launch assistance and so forth) are used, but it's by nomeans an upper limit - most current spacecraft spend their working lives travelling faster than this.

An little bit faster would be an unmanned probe, like the Voyager 1, travelling at 61200 km/u, making a one-way journey 74066 years.

The currently fastest man-made object, the Helios 2, has set a speed record of 252800 km/u.

A journey to Proxima Centauri would even then take 4269 years.

But at the current stage of space technology, the longest space missions that have been initiated are expected to have an operational lifetime of about 40 years before failure of key components is likely to happen. So the ship would run out of power even before coming close to it's target. Power is not actually the main problem - we can build very long-lasting Radioisotope thermoelectric generators. Materials durability is more serious (it's very difficult to build even a terrestrial machine that will function reliably unattended for 40 years).

One might note that science's current best theoretical propulsion system, VASIMR, would be achieving speeds up to 300km/sec, or 1,080,000 km/h.

This would shorten the journey to 999 years.

But that is still beyond the current lifespans of both man and machine.

VASIMR is by no means the best theoretical system - see spacecraft propulsion. Depending on what you're willing to consider viable, anything from ion thrusters to warp drives can be considered the theoretical best. --Andrew 13:32, May 2, 2005 (UTC)

But another proposed method of propulsion, the Nuclear photonic rocket, which has the patential to exceed $c$, would shorten the journey to proxima centauri at about 4.217 years and only needs a few more reserech before being feasable. So andrew; just trying not to be mean but it dosn't matter what kind propulsion you use. It's the amount of energy you use. Fquantum ^talk 14:29, 4 June 2007 (UTC)

• I think most of the text of these edits isn't useful for the article. A more appropriate version would be a short table listing the specific impulse or exhaust velocity for a variety of engines, a reasonable maximum cruising speed, and a flight time to Alpha Centauri, if the information is included at all. A fair bit of the interstellar travel article could stand editing; if I find myself with time on my hands, I may do a rewrite, but for now, the current version looks fine. --Christopher Thomas 00:22, 3 May 2005 (UTC)

Good! I have been waiting to put a table on this article to improve it.

I have just added the table you suspected, but even it was removed. I'm pervasively Suspicios about the removal, but I do have to exept it. Someone else intrested in this article has to reundo and modify this chart and search for citations.

No need for suspicion. That was me, and I explained my actions below. I didn't remove the table from the article, I just commented it out so that it could be worked on in place. PubliusFL 21:00, 27 July 2007 (UTC)

I also think that all(now most) text is not usful to the entire article. That is why I have partially rewritten the Interstellar distances section.Justin Forbes 20:31, 1 May 2007 (UTC)

research

Not trying to stress anyone; but I was here to reasearch this article for a probe Im brainstorming on a journey to Procyon, not to mess it up. If anyone can tell me where I can find a similar article, that has cleaned up sources, than I would be partially proud of the research I have found. — Fquantum ^talk 18:41, 9 September 2007 (UTC)

Interstellar distances section

Why was the example changed from Alpha Centauri to Epsilon Eridani? Alpha Centauri is much closer, and therefore a better example for illustrating the minimal difficulty of interstellar travel. It may be that Epsilon Eridani is the closest planet known at present to have a planetary system, but that's not saying much, because all we can really detect at this point is gas giants. Alpha Centauri is more likely to have terrestrial planets than gas giants, and all things considered is more likely to be the first target of interstellar travel (unless we are actually able to detect terrestrial planets around some other star system in Sol's neighborhood). Also, what spacecraft is capable of making 77 km/s? To the best of my knowledge, Helios 2 was the fastest spacecraft ever built, and depending on what reference you look at, it was only capable of somewhere around 70 km/s. PubliusFL 01:06, 14 February 2007 (UTC)

I herd there was the first earthlike yet discovered. We are likely to to find alot more in the following year. – Fbs. 13 17:10, 28 April 2007 (UTC)

well.. are any of you going to improve this article, or are you going to leave it lacking sources. I am a pervasive expert on this article and does not like anyone to lack sources on true science. I am also an expert on faster than light travel. ..and if any one, even another expert tries to lack inline citations, I do not want to ignore taking it seriously but you know what might happen.Fbs. 13 00:42, 14 May 2007 (UTC)

interstellar distances section (answer)

I am designing a spacecraft. Fbs. 13 19:43, 23 March 2007 (UTC)

I think the fastest propulsion system may make more sence, the propulsion System you may be looking for may be a magnetoplasmadynamic thruster. Fbs. 13 22:45, 27 March 2007 (UTC)

The problem is not what type of thruster you use. The problem is the energy per unit weight of your fuel, as this gives your maximum possible specific impulse, and so your maximum cruise velocity. --Christopher Thomas 02:58, 28 March 2007 (UTC)

Needs current interstellar spaceflight section

This article would benefit more readers if it provided some "grounding" in reality. Specifically, it would be great to discuss those spacecraft which are currently on interstellar trajectories. Discuss how far they've made it, how long it takes to communicate with them (are they yet light-days away?), etc. This is made even more evident by the redirect of Interstellar probe to this article. Sdsds 23:18, 24 March 2007 (UTC)

Perhaps I was wrong. Maybe it is better to leave this article covering the topic it currently covers, and create content at Interstellar probe to cover current spacecraft and spacecraft planned for the near future. I've removed the redirect and put some preliminary content at Interstellar probe to move in that direction. Sdsds 05:54, 31 March 2007 (UTC)

That makes sense to me. Good work. PubliusFL 06:28, 31 March 2007 (UTC)

I've edited Interstellar probe (edit | talk | history | links | watch | logs) for minor factual corrections, and to distinguish between probes that are expected to reach other stars and ones that aren't. It will be very difficult to keep this article grounded in reality (expect lots of edits from people adding fictional references, among other things). If it can be kept encyclopedic, though, it has potential.--Christopher Thomas 08:49, 31 March 2007 (UTC)

The nearest star (interstellar distances section)

The nearest star may not be proxima centauri, which will take 5,043 years with current technology. Since Nemesis may be the closest star to the sun, lying at about 7,140 AU, which may be an L7-type brown dwarf, current technology may send it in just about 247 years, only twice that of a human lifspan! I have also theorized that it may be close enough to have been part of our solar system and, in theory, it may be a more likely place to harbor an earthlike planet about 2.7 earth masses. —The preceding unsigned comment was added by Fbs. 13 (talk • contribs) 02:40, 1 April 2007 (UTC).

If the Nemesis hypothesis is proven, we should definitely change the interstellar distances section. Until then, it's very hypothetical. And what do you mean that you have theorized that Nemesis is "close enough to have been part of our solar system"? The idea that Nemesis is part of our solar system is the whole point of the hypothesis -- otherwise it wouldn't explain cyclical mass extinctions (I'm assuming you aren't Daniel Whitmire or Albert Jackson). PubliusFL 03:44, 1 April 2007 (UTC)

Here is a probable theory that may explain everything: A second shockwave hit Our solar system. It sliced about 13% of the nebulial disk. The partial nebula was gliding through the Interstellar medium and stoped at about 7,145 AU and formed a dark (cool) L7 red dwarf planetary system with two planets –- one was a jovian planet about 13 earth masses; the other (which you may have realized in the top sentence) was an earthlike planet about 2.7 earth masses. The meteors that caused most of the cyclical mass extinctions where probably small OCO impacts on Nemesis c (the earthlike planet) that caused pieces to sling out of the planet (this may be similar to some of the impacts of Mars). This theory may be difficult to understand but you may soon. — Fbs. 13 01:37, 3 April 2007 (UTC)

We understand the concept behind the Nemesis proposal. It's just that the vast majority of astronomers consider the existence of this companion star unlikely, and the contents of Wikipedia reflect that (per WP:NPOV). If the existence of Nemesis becomes accepted as likely - or even a reasonably plausible possibility - then that change will eventually be reflected in this article. Until then, no. --Christopher Thomas 01:51, 3 April 2007 (UTC)

Insert paragraph on von Neumann probes?

I think it would be useful to add a para which refers to von Neumann probes: manned exploration would be very risky unless we know what's at the other end of the journey, and the smallest objects we can currently detect in other solar systems are hot Jupiters; in theory von Neumann probes could explore the whole galaxy in a few million years.

What do other contributors think? Philcha 20:56, 13 April 2007 (UTC)

Make sure it's given space in proportion to references cited. While the idea is well-known (google for "far edge party"), devoting a huge chunk of the article to it would be overkill. The majority of the article should be the same either way (as the timeframes involved are similar whether or not we're on the ship itself, making the technical challenges similar). --Christopher Thomas 22:17, 13 April 2007 (UTC)

Impossible reaction mass requirements of current technology

NASA used to have a page http://www.grc.nasa.gov/WWW/bpp/bpp_INTERSTELLAR.htm (now a 404, alas) which said that a vehicle the size of the Space Shuttle, using the Space Shuttle engines, would need more fuel than the mass of the known universe to reach the nearest star in 1,000 years (in fact it said propellant required = 10¹¹⁹kg, universe = about 10⁵⁵kg). Does anyone know where to find this now, or something similar? Philcha 21:26, 13 April 2007 (UTC)

Not off the top of my head, but that's actually exactly backwards to how you'd want to draw such a table. Once delta-v gets above exhaust velocity, the amount of mass needed grows exponentially, quickly resulting in silly numbers. What you'd do in practice is assume a best possible mass fraction (95% fuel, 99% fuel, etc), and calculate the delta-v you'd get for any given propulsion method. This in turn gives you the shortest practical cruising time you'd get with any given propulsion approach. I got on the order of 1000-4000 years for fission- and fusion-based drives the last time I worked this out. Your mileage may vary. --Christopher Thomas 22:21, 13 April 2007 (UTC)

I like your explanation of how one would go about designing a mission given a particular propulsion tech. But I was looking for a dramatic illustration of why our current "standard" propulsion tech is unsuitable, with citation. Any ideas? Philcha 10:36, 18 April 2007 (UTC)

Go for one that's accurate, not dramatic, is my best suggestion. Find references that say how long a trip would take using a given mass fraction and drive type, and find other references (or ideally the same references) that say what the maximum lifetime of manned and unmanned craft are expected to be. Numbers I've heard are that around 30-ish years is the maximum design lifetime anyone's willing to give to an unmanned probe, and that's only if it has no moving parts (uses RTEGs or similar generation methods). Pointing out that trip time is a hundred times longer than designed lifetime should be sufficient for your purposes.

I don't have references that do this in front of me, and am too busy to search for them, but they'll be out there if you want to handle this yourself.--Christopher Thomas 19:09, 18 April 2007 (UTC)

Fusion drive question

So, the article states that a fusion drive would be capable of attaining around 10% the speed of light. Why is this? Would this be fast enough that the interstellar medium would produce sufficient drag to limit further acceleration? Some other reason? Whatever the reason, it should be stated or at least cited. Harley peters 03:02, 25 April 2007 (UTC)

Mass ratio. Cited here and in linked articles. Michaelbusch 03:09, 25 April 2007 (UTC)

A trip to the farthest planet

The distance from Earth to the other planets of the solar system ranges from about three light minutes to about five and a half light hours. Depending on the planet and its alignment to earth, for a typical unmanned spacecraft these trips will take a few monthes to a little over a decade.

contradicts

Pluto is five and a half light hours and is now classified as a dwarf planet.

Neptune, now the farthest planet, is about 4.7 light seconds away. So if neptune and earth are lined in a temporal constant motion, Than an unmanned spacecraft, using current technology, such as the magnetoplasmadynamic thruster, will get to Neptune in only 2.7 years, depending on hou much energy per thrust you use.

so If this does not get edited into the article, than I will edit it my self and I will cite it. Fquantum ^talk 21:11, 29 May 2007 (UTC)

Good point about Neptune being the farthest planet. Neptune's about 4.2 light hours from the Sun at aphelion, so I changed the sentence to say "about four and a third light hours." I left the "few months to a little over a decade" time frame because it's talking about a typical unmanned spacecraft, with currently used propulsion technology. Magnetoplasmadynamic thrusters are hardly in common use yet. PubliusFL 14:13, 30 May 2007 (UTC)

A reference to gravity control

There is something I directly herd of called a "Central deflecter fuse". It works by spinning the ship on its side; just like a center fuse. Another, called a "synthetic mass generating cover", which lies at, for example, the back of the saucer depth, generates/transports mass to power the sauser it's self.

If there is any reference to the information I revealed, I barely doubt that it has to be cited soon. Fquantum ^talk 21:26, 15 June 2007 (UTC)

Generation ships

I propose to remove all but the first sentence of the first para of section "Generation ships" (i.e. leaving only the definition), because the remainder duplicates later content which is better described and referenced.Philcha 23:16, 13 July 2007 (UTC)

Done.Philcha 23:26, 27 July 2007 (UTC)

Table of "Propulsion methods that could possibly reach the nearest star"

I have commented out this table because it really needs to be discussed here before going live. What sources is it based on? Without sources it smacks of original research. For one thing, the maximum velocities given are based on unstated assumptions about things like mass fractions. PubliusFL 17:30, 20 July 2007 (UTC)

removed citations broken and cleanup tag

if any of you saw templates removed then look on the history page for the latest edit of my account for the article. you might know that I have removed them because the tags were needed a while ago. now the article might not need them because the tags are out of date.-- Fquantum ^talk 13:57, 3 November 2007 (UTC)