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- In the realm of science fiction that has science... Timemaster by Robert L. Forward (who writes science papers with a plot - and that's a good thing).
The main character wanted to get out to the asteroid belt in an accelerated time frame (not relatively accelerated but rather faster than the current slow methods)
> "Sorry, sir," said Mary, the perky nose on her image twitching under her large glasses as she thought. "I'd be glad to turn over all the cable we've been making for the Mars rotovator, but by the time Bull's division could turn it into a cable catapult, you'd be there using the existing system."
> "Can we push the gee limit higher?" asked Randy.
> "Well... yes..." admitted Bull. "We have small express pods we use to send emergency cargo. We can accelerate those at ten times the normal three-gee launch acceleration and get them up to three hundred kilometers a second."
> "How soon would that get me there?" asked Randy.
> Bull, his fingers too large to operate a cuff-comp, pulled an hp pseudocray out of his shirt pocket, and did a short calculation. "Three weeks," he said. "But those capsules accelerate at thirty gees! You'd be squashed flat!"
> Randy paused for a while as he thought. "I've read about deep-sea divers who survived at high pressures by breathing an oxygen-carrying liquid," he said. "If I floated in a tank of that, I could handle thirty gees easily."
> Tony, Mary, and Bull each thought for a while; then all three nodded, although reluctantly.
> "If I were you, I'd check with some medical and diving experts first," said Tony. "It could be hard on your lungs."
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Granted, that's science fiction and there are some real problems with that approach too...
https://en.wikipedia.org/wiki/Liquid_breathing#Space_travel
> Acceleration protection by liquid immersion is limited by the differential density of body tissues and immersion fluid, limiting the utility of this method to about 15g to 20g. Extending acceleration protection beyond 20g requires filling the lungs with fluid of density similar to water. An astronaut totally immersed in liquid, with liquid inside all body cavities, will feel little effect from extreme G forces because the forces on a liquid are distributed equally, and in all directions simultaneously. Effects will still be felt because of density differences between different body tissues, so an upper acceleration limit still exists. However, it can likely be higher than hundreds of G.
> Liquid breathing for acceleration protection may never be practical because of the difficulty of finding a suitable breathing medium of similar density to water that is compatible with lung tissue. Perfluorocarbon fluids are twice as dense as water, hence unsuitable for this application.
We're not at the point where we can launch at hundreds of Gs yet (and I'm not sure I would want them to be centripetal Gs initially either - that sounds very not fun) ... but when we get to the point were we want to launch a person into space in the direction of another planet at 10 or 20 or 30 Gs of initial acceleration, this is likely something to be revisited.
- All the Myriad Ways - by Larry Niven https://archive.org/details/Galaxy_v27n03_1968-10/page/n31/m...
Not a time travel premise, but rather a parallel universe approach... for that I'd suggest The Theory and Practice of Time Travel which expresses Novikov self-consistency principle ( https://en.wikipedia.org/wiki/Novikov_self-consistency_princ...) (see also https://en.wikipedia.org/wiki/Niven%27s_laws#Niven's_Law_(Ti... ).
I'd also suggest a watch of Time Travel in Fiction Rundown - Minute Physics https://youtu.be/d3zTfXvYZ9s
If you want something longer on the subject, then Timemaster by Robert L. Forward is a good book to read ( https://archive.org/details/timemaster00forw/page/n11/mode/2... ). It begins with:
> There exist semieducated but obstinate people who have raised the concept of strict local causality to godhead, and attempt to use such words as "obviously" and "it only makes sense that . . ." in an attempt to "prove" that their version of causality cannot be violated, and that any sort of time machine is logically impossible. From my reading of the scientific literature, they are wrong. If I receive a letter from this sort of person complaining about the "impossibility" of the time machines in this novel, I will throw the letter in the nearest wastebasket . . . unless the letter is accompanied by a reprint of a scientific paper published in Physical Review (or any other reputable, refereed scientific journal), written by the person writing the letter, which proves that the paper "Cauchy Problem in Spacetimes with Closed Timelike Curves" by Friedman, Morris, Novikov, Echeverria, Klinkhammer, Thorne, and Yurtsever, is erroneous.
You'll note that history in that story remains consistent... and you can't kill Hitler.
- Thank you! The first thing I did when coming to this thread was search for posts containing "Robert Forward", as any discussion of negative inertial mass is incomplete without mentioning his work. So, kudos.
Anyone interested in the implications of negative mass should probably check out Timemaster, a sci-fi novel by Forward. Negative mass can hypothetically do some interesting things. Things such as allowing lightspeed travel by matching negative mass to positive mass in equal amounts, leaving a non-photon object with rest mass = 0, or producing energy by accelerating negative mass to high velocities.
Unfortunately, Forward is much better as an idea guy than he is as an author. The scene where the hero travels back in time and has a threesome with himself and his wife is a bit awkward...
- I am curious what a earth to space launch rotovator that is capable of doing 30g would have for its overall acceleration profile.
Robert Forward (the author of Timemaster) was a physicist and I would do a check of his anatomy related topics before getting into one... but I would be confident of his math.
He wasn't unfamiliar with the technology being used.
https://en.wikipedia.org/wiki/Robert_L._Forward
> He then went to work at the research labs of Hughes Aircraft, where he continued his research on gravity measurement and received 18 patents. He took early retirement in 1987, to focus on his fiction writing and consulting for such clients as NASA and the U.S. Air Force. In 1994, he co-founded the company Tethers Unlimited, Inc. with Robert P. Hoyt, where he served as chief scientist and chairman until 2002.
https://en.wikipedia.org/wiki/Tethers_Unlimited,_Inc.
> Founded in 1994 by Robert P. Hoyt and Robert L. Forward, Tethers Unlimited began developing products based on space tether technologies, including concepts for removal of space debris and momentum exchange tethers for launching payloads into higher orbits. TUI has since broadened its suite of technologies to include power, propulsion, actuation, and communications systems for small satellites, robotic technologies for on-orbit fabrication and assembly, optical fiber winding and deployment, software defined radio communications, and 3D printed radiation shielding.
...
And so, on his word, I'd suspect that it would not be unreasonable to do a fluid breathing 30g ... given the right fluid breathing setup. The rotovator setups are looking at significant fractions of a day for earth capture to space release (6 or 12 hours). I don't think there would be human significant jerk, snap, crackle, and pops either. Though again, I'd be curious to see that acceleration profile (not that I'd ever be doing it myself).
- > Greg Egan is often cited as one of the current greats when it comes to hard sci-fi.
I'd also suggest a good look at Baxter's books and Robert L Forward's too.
I've jokingly called Forward's books science papers with a plot. Timemaster starts out with:
> There exist semieducated but obstinate people who have raised the concept of strict local causality to godhead, and attempt to use such words as "obviously" and "it only makes sense that ..." in an attempt to "prove" that their version of causality cannot be violated, and that any sort of time machine is logically impossible. From my reading of the scientific literature, they are wrong. If I receive a letter from this sort of person complaining about the "impossibility" of the time machines in this novel, I will throw the letter in the nearest wastebasket... unless the letter is accompanied by a reprint of a scientific paper published in Physical Review (or any other reputable, refereed scientific journal), written by the person writing the letter, which proves that the paper "Cauchy Problem in Spacetimes with Closed Timelike Curves" by Friedman, Morris, Novikov, Echeverria, Klinkhammer, Thorne, and Yurtsever, is erroneous.
My take on it is more of a "what is the focus of the story?" Is it the soft sciences? Psychology and sociology and politics ... and the Foundation.
Or is it one more of challenges met with the STEM disciplines of physics and astronomy and biology?
It's also not a "it is either a this or that." Some books can be both and I think that Clarke is a prime example of this. 2001 is as much of a story of psychology as it is about astronomical distances and the ship needed to accomplish that goal. The Songs of Distant Earth is about two cultures clashing ... with the real problems of engineering a ship to travel (it's a softer story than it is hard).
Protector by Niven likewise scores high on both the soft and hard scales.
Foster tends to higher on the 'soft' side of the scale, though sometimes it edges up there with some real biology and the limits of technology are sometimes real limits.
And so, it is "are the challenges that the characters surmount solved with tools developed from the soft or hard sciences?"
"Use the Force Luke" is not a hard science solution.
- Robert Forward. https://en.wikipedia.org/wiki/Robert_L._Forward
In the preface to Timemaster (which features time travel and various paradoxical events), he states anyone who wishes to argue against his hard science use of time travel must first have a published article in a peer reviewed journal refuting a particular paper.
