For some reason writers seem to think a spaceship needs to have the engines on all the time to move in space. That bastion of scientific accuracy, the Avengers series, states so explicitly in “Avengers: End Game”. In the first few minutes Tony Stark tells how he modified the power source to get 48 hours of thrust but now he is “dead in the water” or “dead in space”. The ship is shown motionless against the starry background.
I think anything Tony Stark built will be going like a sonabitch after 48 hours of thrust.
If acceleration and velocity worked like it worked in real life, that would be true, but you’d almost have to put up some warp field or something to allow you to accelerate to interstellar speeds quickly enough to make it meaningful and not kill the passengers. And it’s plausible that that needs continuous energy.
On the other hand, if you merely see it stopped motionless around the planets, the objection has greater weight, since we’d be able to meaningfully travel through the solar system under impulse drives that were limited to 1g or slightly higher.
The ship could well be traveling at thousands of miles per hour in that shot on momentum. At sub-light speeds, the ship is going to appear motionless against a background of stars, because the distances are so vast. In order to go anywhere in their lifetimes, they would need some sort of faster-than-light drive. The FTL drive might have only produced 48 hours of thrust, and now they’re “dead in the water” because the FTL drive needs to be in continuous operation to keep them in “warp” or whatever their FTL tech is.
I suspect, though, that the screenwriters were only accidentally right about all of that, though. I suspect they intended the scene exactly as you were interpreting it, that without continuous thrust, a space ship would be like a sailing ship, and just drift aimlessly or hang motionless in space.
This is such an obvious error that I am surprised I never noticed it before on countless shows and movies. I’m sure that the same thing happened back on Star Trek TOS at some point.
What a great turn of phrase! Now I want to publish a compendium of short stories set in deep space and title it “Tales From Flat Space”.
Or maybe write my own (with proper science, of course).
Then when people see one of my later books they’ll say “Oh, is this another one of his Flat Space books?”
And that is a general problem with the presentation of space travel in general. Even The Expanse, which hews toward something approaching scientific accuracy (at least the writers acknowledge orbital mechanics and thermodynamics even if they don’t actually apply them as realistic constraints when drama and pacing require otherwise) has implausibly efficient high thrust engines (the Epstein drive) allowing rapid flight to the far reaches of the solar system instead of the months it would take even with constant thrust ion engines and the requirements for extracting and carrying propellants.
The reality and limitations of actual spaceflight would be prohibitive to dramatic storytelling, and of course traveling to even the closest star systems in anything less than several human lifetimes requires superluminal travel (or relativistic time dilation, which is problematic if you ever want to return to Earth only to find that dozens or hundreds of years have passed). Most cinematic space-based science fiction is based upon “Age of Sail” modalities of travel and trade, both because they are familiar to viewers and because they provide a useful substrate for drama and conflict.
As for the Marvel Cinematic Universe as a space opera milieu, I don’t think there is any pretense that it in any way based on science. From a “genius billionaire playboy-philanthropist” who builds a microfusion reactor in a cave from spare parts and a guy who transforms into an indestructible giant green rage monster to a literal witch and a Norse god-being who can fly around the universe with his magic hammer, the only mentions of actual science in the films are just a nod to the comic book sensibility of it, e.g. exploding redlined gauges, sparking machines, invisible flying aircraft carriers and so forth. There isn’t much point in getting hung up on implausible science fiction tropes because the entire premise—that superpowered and virtually indestructible heroes will save the world from the threat of cosmic villains—is fundamentally preposterous.
If every science fiction movie and franchise attempted the same degree of technical fidelity as 2001: A Space Odyssey, you wouldn’t hear anything about it because the general public would find it “too boring” to watch. Even movies that attempt to be scientifically plausible presentations of spaceflight like Apollo 13 or The Martian take liberties with fact and science to make a more compact and coherent story or to explain how the protagonist could survive when they should have died five minutes into the film. The space environment is hazardous and rapidly lethal, and finding some conflict that puts the characters in jeopardy but doesn’t immediately immolate or asphyxiate them almost inevitably requires some plausibility-bending storytelling.
Real space travel is like moving over a mountain. It takes a lot of energy to get up there. But once you’re there, you can turn off the engine and you’ll move along at a good speed without any effort. The only problem you’ll have is being able to slow down as you approach your destination.
No, the problem is how they would possibly maintain those constant thrust levels without using a massive amount of propellant. It is evident from the ship layout and the fact that they almost never reference needing to acquire fuel that the fictional Epstein Drive must be enormously more efficient than even a very efficient nuclear fusion thermal rocket. At 0.1⋅g acceleration for 24 hours, a propulsion system with a specific impulse of 10,000⋅s would still require that nearly 9% of the mass of the vessel be propellant, and a 1.0⋅g it would have to be almost 60% propellant. To achieve the kind of constant thrust for days or weeks while using only the small amount of propellant that the ships actually carry means the Epstein Drive must have an efficiency approaching 1,000,000⋅s, which is ludicrously beyond any kind of thermal rocket and would give it an effective exhaust velocity exceeding 30% of c, for which the throughput specific power level would be enormous.
Note that this isn’t limited to The Expanse; the vast majority of ‘hard’ science fiction using fusion engines or some similar thermal rocket propulsion (including Larry Niven) make the same oversight, notwithstanding of how a space vessel could possibly reject the enormous amount of non-working thermal energy such a high temperature energetic process would produce. Of science fiction authors I can only recall Arthur C. Clarke and Stephen Baxter getting this correct. Any really high acceleration vehicle would have to use some kind of non-inertial propulsion or some incredibly high specific power output non-thermal energy source that would have be well beyond what could be generated via ‘normal’ nuclear fusion.
Accelerations in both the book and TV series are exaggerated by approximately a factor 10. That is: At one tenth of the stated acceleration (e.g. 0.1g rather than 1g for cruising) the travel times would be roughly correct.
The authors use extended high g burns for dramatic effect throughout the books. Probably an innocent calculation error when starting to write the books, the authors choose to “keep it consistently wrong” by reporting the relative travel times and distances correctly, but the acceleration consistently too high.
Or just that it doesn’t matter if they describe travel time v. acceleration correctly when they’re using a magical drive?
No, you missed my point–in the books, the travel time between destinations was shown to be weeks or months, not rapid. In fact, the voyages took much longer than they would in reality given the stated acceleration.
In Film IV [the Whales one] it did-the probe comes along, disrupting power to a space station-and a small shuttle instantly starts to slow down in space dock.
As an example of travel times, in Cibola Burn (the book of the previous TV season) it took the Rossi 73 days to travel from the ring gate to the colony world.
The movie Lifeforce actually gives a reason for having the engine on all the time—the opening narration explains that the HMS Churchill is propelled with “constant acceleration,” which creates artificial gravity on the trip to Halley’s Comet. I thought that was interesting.
Unfortunately, they forgot about the deceleration part. There’s no mention of turning the ship around and slowing down. The Churchill gets to Halley’s Comet and they simply shut down the engine and stop.
