Spacecraft Speed

As a science fiction writer, I’ve generally tied to keep my “space drives” at least tenuously related to scientific reality as we currently know it, but that distance is likely more attenuated than many readers realize.

In doing some research for my next book, I came across the speeds of the fastest outbound human space craft, which is currently Voyager 1, at 38,610 mph, or roughly 10.7 miles per second.  For those who are interested, the speed is measured outbound, because anything launched toward the sun will have its velocity increased by the sun’s gravity.  As an example of that, when Comet ISON was discovered in 2012, between the orbits of Jupiter and Saturn, its inbound speed was calculated at roughly 10.5 mps, but by the time it reached perihelion, that speed was between 63 mps and 360 mps (or 1,300,000 miles per hour)[that depended on who was doing the calculating, because exact figures were not possible, given that ISON was either so close to the sun or actually on the far side of the sun from earth at the time around perihelion]. The fastest sun-grazing comets could theoretically reach a speed of over 400 mps.

If a human spacecraft could attain and maintain such a speed headed out of our solar system, it would still take over 118 days to reach the average orbital distance of Pluto from the sun… and something like 2,300 years to reach Alpha Centauri [those are rough calculations; feel free to refine them].  These figures indicate why SF writers tend to focus on interstellar travel through “jumps,”  “warps”, wormholes or the like, especially since there’s the not-so-small problem of what happens when one encounters a comparatively immoveable object at that velocity.  While space is largely empty, it appears as though most solar systems have all sorts of objects scattered around their periphery and approaching any other system with that sort of velocity would be problematical.  So, of course, we writers come up with screens and shields, and never mind the energy consumption required for such powerful drive systems and the requisite shields.

Then, too, according to Einstein, any object approaching the speed of light would also gain a huge amount of mass, possibly infinite mass… and there’s not enough energy to push that mass.  So… we’re back to getting around the speed of light and all those pesky relativity problems.

Theoretically, from what I’ve read, a so-called Hawking wormhole could be used to thwart the speed of light limitations.  There’s just one catch – to create one would require the energy of a small black hole… each time it was used.

Is it any wonder that more fantasy and less hard SF is being written?  And that the vast majority of all the space operas [including, I must admit, some of my own SF] ignore those facts? 


6 thoughts on “Spacecraft Speed”

  1. AndrewV says:

    I love it when you write articles like this. SciFi has an opportunity to be a teaching tool and it saddens me when writers do not provide at least some actual science in the stories.

  2. Wine Guy says:

    There’s no reason to think that these problems are insurmountable… merely very difficult. Just because we can’t think of an answer now does not mean it does not exist.

  3. Robert The Addled says:

    There is a decent mix.

    One of my other favorites David Weber, uses real (or reality based) physics along with the literary workarounds. There are several active forums on Baen, and a good chunk of the discussion IS the tech.

    As a result of the writing and the forum combined, some of the (Weber) books have tech addendums comparing ship size, how the drives ‘work’, etc. Both writers make the assumptions that the power is available in some fashion, but also have delays/tech limits due to power requirements.

    The Multi-author (Flints, Weber, many others) 1632 universe works the same – real tech, within the tech capabilities (whether or not 2 and 2 had been assembled in the subject year to actually make 4) of the years in question, mixed with the tech/general science brought back from the modern day.

    Where real science is input, I think SOME of what we are seeing is Jack of all trades (JOAT) meets Renaissance Man – the authors research into the real physics/science/economics becomes integral to their writings.

  4. Wayne Kernochan says:

    You might be interested in a book of essays Robert Forward (I think; I believe he was a practicing physicist) wrote shortly before his death. According to him, we could (and have) trapped particles of antimatter in a “magnetic trap”; these carry an enormous amount of energy that could be used to power a spaceship for almost indefinite distances. The trick (given that acceleration produces gravity) was to (a) counteract the gravity induced when the spaceship’s acceleration was greater than 1 gravity (Forward had some more speculative ideas on this) and (b) to amass enough antimatter (at present, it can only be done via CERN, which is busy with other matters, and would take a decade or two to amass enough energy for one spaceship).

    But to go to Alpha Centauri in a decade or two, given that type of acceleration/deceleration, is therefore perfectly doable — just hugely expensive. And, of course, there’s Krugman’s paper on how interplanetary/interstellar commerce would never pay (without FTL).

  5. Daze says:

    There’s always the Cities in Flight alternative, which is keeping your characters alive for thousands of years so they can spend a hundred years getting from one place to another … Then Blish still has to have the Dirac FTL communications contrivance to have the characters interact with each other in relevant timeframes, but that is at least imaginable with extensions of current science via entangled stufflets.

  6. Stephen Van says:

    I recall reading an article a while back by NASA relating to the Alcubierre drive, or in classical sf terms Warp drive.

    From my understanding of the principles behind the theoretical engine, space is warped around the vehicle so that you slide in the general direction of your destination.

    The problem brought up with analysis from the University of Sydney claims that using a warp drive of this design comes with a drawback. Specifically, it could cause cataclysmic explosions at your destination. e.g. If nothing else we have a nice shiny new weapon to destroy any enemies we may discover or make through our own failings.

    Supposedly the nature of the warp field would either crush or push objects in the way out of the path of the approaching ship.

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