Gfrktyl

If all of the crew and passengers of an interstellar craft were in suspended animation except prior to Earth departure and just before destination arrival, would they need artificial gravity (through some from of spin) for the length of the journey?

Also please let me know if there's a better place to ask this question. I don't want to step out of context.

Need? No. Want? Yes.

From real life:

Science Results for Everyone
Maintaining strong muscles is a big enough challenge on Earth. It is much harder to do in space where there is no gravity. Calf muscles biopsies before flight and after a six months mission on the ISS show that even when crew members did aerobic exercise five hours a week and resistance exercise three to six days per week, muscle volume and peak power both still decrease significantly. Overall, the data suggest that current exercise countermeasures are not enough. The addition of a second treadmill and the Advanced Resistive Exercise Device (ARED) along with more rigorous exercise regiment are giving good results in preventing muscle loss and preserving overall muscle health.

-Effect of Prolonged Space Flight on Human Skeletal Muscle (Biopsy) - 08.15.18 -NASA

Unless your sleeper technology can make up for the atrophy of muscles that's normally seen in both comatose patients AND the atrophy seen in Active microgravity residents, the addition of artificial gravity would reduce this problem to coma patient level, which could be treated with neuromuscular electrical stimulation.

But neuromuscular electrical stimulation doesn't work for bone mass losses (Osteoporosis) as well, which is also another problem of microgravity. So your sleeper tech would also need that. Artificial gravity would make it a non-issue.

So need? No, your sleeper tech can adjust for the medical issues or have your travelers arrive skinny and weak. But you probably want it.

Whatever the source of the gravity, it should be about Earth normal 1G. Lower gravity would cause less stress to the body and still lead to skeletal-muscular mass losses (at a lower rate), and high gravity causes issues with blood pumping and stress to tissue. Sustained high gravity force can kill a human.

Would a sleeper ship need artificial gravity?

No

There's only one real reason people want artificial gravity during a space journey.

To avoid the muscle atrophy etc arising from micro gravity.

But assuming that the suspended animation suspends (or at least significantly slows) all biological functions at a cellular level (which is the way it's most usually depicted in sci fi) there's no plausible explanation for why there would be any muscle (or other) atrophy from zero g during the journey.

So they wouldn't need it.

Which doesn't mean a sleeper ship won't have it, just that they probably won't have any artificial gravity they have got turned on during the bulk of the journey.

A ship on a regular shuttle run might not have any if no one is expected to spend more than a few hours awake in zero g either end of the journey, while an exploration vessel that might loiter for an extended period above a planet after arriving probably will (if the tech is available).

Absolutely Yes

Humanity was not designed for microgravity.

Life in the microgravity environment of space brings many changes to the human body. The loss of bone and muscle mass, change in cardiac performance, variation in behavior, and body-wide alterations initiated by a changing nervous system are some of the most apparent and potentially detrimental effects of microgravity. Changes to bone are particularly noticeable because they affect an astronaut's ability to move and walk upon return to Earth's gravity. (Source: NASA)

In a nutshell (and building on CDE's excellent answer), all of the following suffer in microgravity, whether you're sleeping or not.

• Bones


• Muscles


• Cardiovascular system


• Nervous system

And, based on the very brief mention of "variations in behavior," the brain itself suffers for lack of gravity.

The simple reality is that long-term space travel will require 1G gravity or Bad Things happen. Sleeping doesn't solve the problem. In fact, extrapolating from the explanations, thanks to the loss of active psychological and physiological activity, it might be a great deal worse.