# Lightspeed travel survivability [closed]

In my sci fi novel, a technologically advanced version of the human race is capable of harnessing and creating large amounts of antimatter for interstellar travel at 99% the speed of light , accelerating to those speeds in 10 hours before activating an alcuberre spacetime drive. However, with some rough math, I estimate that acceleration to that speed would put around 850g of force on the squishy humans inside the craft, causing them instant death. Unfortunately, due to the nature of the plot, the humans cannot undergo any genetic or cyborg upgrades allowing them to survive high speeds, in addition, in order to make sure the protagonist doesn't waste months just flying through space accelerating to the minimal speed required for the warp drive to activate. So here's the problem: How could a spaceship accelerate humans to 99% the speed of light in 10 hours without compromising the passengers on board (no physical modifications to the passenger allowed)

• If you're interested in hard science solutions, wouldn't it be just much simpler to avoid the need for a photon drive of unspeakable, planet-liquifying power fueled by planet-shattering amounts of antimatter (because that's what you need if you want to get to .99c promptly) and have a slightly longer speedup time and a slightly lower jump-starting speed for your warp drive? I mean, all these variables are within your control, so why not just tweak them to make stuff work? Feb 24 at 14:54
• Also worth noting that if you can get to .99c in 10 hours, then the business of making relativistic kill vehicles becomes straightforward, and that's not a good place to be. Feb 24 at 14:55
• Zetrox, did you read the hard-science tag wiki before using it? Every answer you've been given fails that tag and are quite literally under threat of deletion because of it. The hard-science tag does not refer to a literary genre. What it does is force answers to prove themselves with mathematics and citations to accredited sources (like scientific papers). Did you actually need an answer that strict considering how fanciful the premise is to begin with?
– JBH
Feb 24 at 17:24
• I’m voting to close this question because hard-science answers to this are impractical. Feb 24 at 17:40
• Does this answer your question? Can a human crew handle cyclic extended high relativistic speed operations? Feb 24 at 18:03

Somewhat of a frame challenge: at this tech level, human bodies are fully expendable

At the beginning of the trip, passenger's consciousness gets transferred to a more sturdy storage (it could even be something like Amazon Web Services interstellar cloud). During acceleration/deceleration, everything is reliably secured. Once we are out of high g, new instances of human bodies are created and initialized with stored consciousness. Passengers wake up just like they do from a more traditional hypersleep.

Full Body Liquid Immersion

This doesn't actually work completely. I've been looking around online and estimates seem to suggest that this technique will, at best, work for around 200g of acceleration. But, hey, that's a pretty impressive 200g, and shouldn't push the acceleration window that much longer.

The theory behind full body immersion is kind of simple, it just comes down to shock absorption and support. If you submerge a human in a tank of shock-absorbent liquid (not water, it needs to be a little better than that), then the liquid will act to transfer the force equally as well as support the body under the intense strain.

The only problem is breathing, because the lungs will collapse at the point of 200g, so you need to fill it with liquid as well. Trouble is we haven't exactly cracked the liquid breathing yet, but if you assume that this society has, then you just need to dunk the subject in a specialized immersion pod, and there you have it! Admittedly, like I mentioned earlier, I'm not sure this method will stand up to the full 890g, so if anyone has a method that does, that's a better answer.

There's a useful question on our sister site that will give you more background: Space Stack Exchange, which is what I'm basing the majority of my answer on.