Wikipedia:Reference desk/Archives/Science/2019 April 17

= April 17 =

Interstellar Propulsion
I wish you all a good day!

I was wondering if actual technologies exist, which could allow humanity to travel across the galaxy. I recall that a good friend of mine has had a book during our time at high school which dealt with such ideas and it offered quite outlandish ideas. I remember that he spoke of a "photon rocket", which he called "the only existing way to actually travel across the known universe". I was wondering if there ever were plans to build a real interstellar spaceship.

Thank you most kindly for your answers!--2A02:120B:2C17:3CA0:D43D:F270:18DE:3724 (talk) 10:06, 17 April 2019 (UTC)


 * There are a number of technologies that could be described that way, and I would point you towards our article on Laser propulsion. As mentioned there, testing is ongoing for several of these. In the near future, you are only likely to see them used to propel very very tiny probes. Generally, the real devil in interstellar travel is the rocket equation, i.e. that fuel costs increase exponentially with total required delta-v for the payload. Pushing a colony ship to a good fraction the speed of light using conventional rockets would take a fuel tank heavier than the observable universe, for instance. Terrible. But if you can propel a spacecraft by shooting it with a laser beam from a ground station, and you can keep that beam on target over a considerable distance, you are kind of cheating - you don't need to take your fuel with you, and in scientific terms that saves hella weight. Someguy1221 (talk) 10:24, 17 April 2019 (UTC)


 * Possibly he is thinking of Breakthrough Starshot, which is not a way for people to travel but is at least a plan. The closest to a plan for humans I recall is Project Orion and subsequent proposals for nuclear pulse propulsion which seems like it would be ... inelegant at the logistical level.  But reading through that article I see some interesting developments toward a fusion rocket which might be more reasonable. Wnt (talk) 11:31, 17 April 2019 (UTC)


 * Even with a ship taking thousands of years a big problem would then be slowing down at the far end. My guess is that the initial effort to make a workable system would be to somehow get robots to the far end so they can build something like a laser system to slow things down as they reached there. A huge undertaking but mainly of technology rather than materials. As to sending grown people - unlikely. More likely grow people at the far end. Dmcq (talk) 12:14, 17 April 2019 (UTC)

Thank you very much, Gentlemen!--2A02:120B:2C17:3CA0:7443:7455:66DD:2543 (talk) 18:06, 17 April 2019 (UTC)


 * Or just transform into a machine civilization and then upload the digital brain contents via radio or laser beams to another civilization far away. There is then no need to build any spacecraft. The transmissions can be one way communications. You can just send a message that explains how to decode the next message after which the next message containing the data is sent. That data then also contains the instructions on how to build a machine that can run  the algorithm that will render some particular individual. This entire  message is then  repeated over and over again. Count Iblis (talk) 21:58, 17 April 2019 (UTC)


 * rather less feasible and with unknown technology and unknown aliens! At least what I was saying will soon be feasible and could be replicated in quantity. The only real downer is that the various steps would take a very long time. Dmcq (talk) 22:29, 17 April 2019 (UTC)


 * It could actually be faster to communicate with aliens to go there than send messages. That is, people on a ship going close to the speed of light would have time dilation effects which would make the decades, centuries, or millennia seem like only years aboard the ship.  Of course, those back on Earth wouldn't get in on the communication any sooner. SinisterLefty (talk) 19:17, 18 April 2019 (UTC)

There are different ideas like the Bussard ramscoop as a method of interstellar travel, i.e. taking some number of years to reach nearby stars that are a few light-years away. Travelling across the galaxy (diameter around 185,000 light years iirc) without faster-than-light travel is something else entirely. I can't even think of any science fiction where that happens, though there probably is some. 67.164.113.165 (talk) 21:08, 18 April 2019 (UTC)
 * Tau Zero comes to mind. 93.136.13.167 (talk) 17:24, 19 April 2019 (UTC)
 * Thanks! I might look for that sometime.  I had seen the title before but didn't know what the book was about. 67.164.113.165 (talk) 02:00, 21 April 2019 (UTC)


 * Interstellar travels are impossible, there are many reasons for it: hard radiation, gamma rays, proton showers, GRB's, junk in the space, etc. Even the radiation in a near earth orbit changed an astronaut's DNA. Traveling to Mars and back will raise a chance to have a cancer by 5-10%. If moving at the speed of Voyagers I or II to reach the closest stars will require 80,000 years. Enormous star ship and a crew of thousands need to be considered as initial condition for such a voyage. Imagine the next generation may ask: "What are we doing in here?" We will never move beyond our mother earth. AboutFace 22 (talk) 23:08, 22 April 2019 (UTC)