# How long could a human stand 3X gravity

#### GhostDoggy

##### Senior member
I'm figuring that if a craft left Earth orbit with an acceleration of three times that of gravity so that the craft's occupants would be crashed then how fast would they get at the mid-point of any journey in order to do a 180º ship-flip to slow down at the same rate. Let's assume the destination is local, like Pluto and we are just traversing the approximate planet-Sun radius (3.6 Billion for Pluto and 0.093 Billion for Earth).

This ouwl mean an radially-outward travel is roughly 3.5 Billion miles. Simple math, but the time is still long vs. the gravity getting unbearable for long-term exposure.

#### stardrek

##### Senior member
I don't think there is any definitive answer to this but NASA has discussed this exact method with an acceleration/deceleration or derivation thereof of 9.81 m/s^2 so as to simulate the same amount of gravity we have hear on earth.

As a side-note can I say "amount of gravity"? Can you quantify it in that way and express it like that grammatically?

#### Smilin

##### Diamond Member
Navy / Airforce probably have some good data on this somewhere.

For someone simply being a "passenger" and perhaps laying around they might withstand this for weeks. Your cardiovascular system is gonna be hurting. Digestion, kidney function all that good stuff would have to be watched too.

Just speculating. Don't really know

#### sdifox

##### No Lifer
depends on the period. If you accelerate slowly, working your way up to 3G say in a year, I would say your body will adapt, which proper physical prep. If you do one of those 0 to 60 things, not going to last too long.

#### alcoholbob

##### Diamond Member
You can't maintain continuous acceleration without a crazy (undiscovered) fuel source. You can certainly maintain a lot of speed in space with ease.

#### Nithin

##### Senior member
that doesn't sound right. why would we need any energy to maintain speed in space? there is no deceleration is there?
shouldn't any energy go directly into acceleration?

#### iwantanewcomputer

##### Diamond Member
I imagine humans could withstand ~1.5 G's for years at a time as long as you moved around frequently with respect to the acceleration direction. (like not spending all day standing up) this would be more of a problem colonizing other planets with higher gravity cause we are not likely to come up with engine/fuel sources that can sustain that aceleration for long.(think how long a saturn V rocket lasts)

#### gbuskirk

##### Member
We're talking about continuous acceleration, not continuous velocity. It takes energy to accelerate a mass.

#### GhostDoggy

##### Senior member
We are talking about the human body, and mind, capable of standing three times the natural gravity for humans for long periods of time. We are NOT talking about spacecraft--go talk about that somewhere else. I want to assume some a-hole of a physicist came up with the means, but I want to know if the human body can withstand long periods of 3G, and if so how long of a period would that be. I do not want to talk about feasability of propulsion, but rather the human condition and its limitations.

BTW, are not today's astronauts subjected to, all be it for a very limited amount of time, to something in the 3G neighborhood, or was that the Apollo experience? I know is not deemed a difficult thing to sit in a chair and be accelrated at 3Gs, but that isn't what I had in mind for practical application--unless we plan on slithering around the floor on our backs.

Smilin, you mention that Navy people go through this all the time. Can you elaborate on this? I'm not aware that they sustain 3Gs continuously in one direction. I can see where the add force of a swelling sea might have minute periods of >G on the body, but this is rollercoastering in effect and not sustain for long periods of time.

#### DrPizza

##### Administrator Elite Member Goat Whisperer
Originally posted by: sdifox
depends on the period. If you accelerate slowly, working your way up to 3G say in a year, I would say your body will adapt, which proper physical prep. If you do one of those 0 to 60 things, not going to last too long.

I think I understand what you mean - you don't mean "accelerate slowly", but rather mean "slowly increase the acceleration from 1g to 3g's over the course of a year." (3rd derivative of position = time rate of change of acceleration = jerk... just an oddity I toss at the physics students each year). So, you mean, "If you jerk slowly, working your way up to 3G say in a year..."

And, for what it's worth, other than your idea, I doubt the human body can withstand 3g's for very long. (with respect to the length of time of such a trip) - At a guess, a few days. I think the circulatory system would be the weakest link. It wouldn't be hard to experiment with though... just go purchase one of those carnival rides where you stand up and spin in a circle... set the controls to keep it on for a week, climb aboard, have fun!

#### Peter

##### Elite Member
The most fuel economic way of long-distance travel in space is SLOW acceleration over half the distance, and then SLOW deceleration over the other half.

Fuel consumption increases way more than linearly with propulsion - simply because for a faster flight that consumes more fuel, you need to propel all that extra fuel along with the payload, which requires stronger thrust which again consumes more fuel.

#### sunnpat

##### Junior Member
A fighter pilto can execute 5g turn and actually if you are on a rollercoster yoou probably experience about 2-3g.
How the human body would react would be interesting. The trunk muscles would probably grow bigger (like a body builders) as they would have to support a greater weight (different to mass). Probably at risk of blood pooling in the veins of your legs, due to the increased gravity but this may be overcome by a number of methods. Higher Blood preasure, a greater number of valves in the veins, better assisted flow via actions of the skeletal muscles. Not sure about he kidneys and intestines though.
Human body is very good at adapting to the environment it is in.

Sunny

#### GhostDoggy

##### Senior member
Originally posted by: sunnpat
A fighter pilto can execute 5g turn and actually if you are on a rollercoster yoou probably experience about 2-3g.
How the human body would react would be interesting. The trunk muscles would probably grow bigger (like a body builders) as they would have to support a greater weight (different to mass). Probably at risk of blood pooling in the veins of your legs, due to the increased gravity but this may be overcome by a number of methods. Higher Blood preasure, a greater number of valves in the veins, better assisted flow via actions of the skeletal muscles. Not sure about he kidneys and intestines though.
Human body is very good at adapting to the environment it is in.

Sunny

You are using examples of impulse sitautions and not sustained conditions. We've tested humans to +9 g's, but not four-to-six months duration of 3g's.

#### Gibsons

##### Lifer
I think some effects would simply be the reverse of what we see from long term living in zero G.

So, increases in bone density, muscle tone, etc. which sounds good, but...

People with weak circulations would likely see swelling in their feet/ankles (maybe severe, some people might need to wear G suits), the cardiovacular system would certiainly be taxed. Another thing is it would just be dangerous. Just a little stumble and you're more likely to fall, and a fall might frequently result in broken bones, even among young and healthy crewmembers. Dropping something on your foot would be something to avoid at all costs. Ouch.

#### alpha88

##### Senior member
I think the human body would not have a difficult time adjusting to a gravity of ~3g.

Here is why:

a) The body can withstand bursts of significantly more than 3g, so I'm confident things won't break over time.

b) The body can handle higher G for durations (minutes, hours) with no significant side effects.

This leads me to believe that since the body performs just fine for hours at higher gravity (with no signs that trouble is around the corner), then if exposed to higher gravity for longer durations (days,weeks) the body will continue to perform just fine, and after months and years, the body will make minor adaptations to the new gravity.

I expect that one would grow stronger bones and muscles. I'm not sure how the circulation system will change, but skeletal muscles should help keep blood from pooling at your feet.

#### Vee

##### Senior member
I think there are very good reasons to assume that humans cannot adapt to 3g. Unless you're lying down, my guess is that you'd develop various brain damages due to lack of oxygen and nutrition rather soon. And if you're lying down, you'll have other circulation problems soon enough. Just like in 1g, but worse, because the tissue under pressure will be more so.

But the question seem to me rather irrelevant. 1g is plenty for space travel. ...If it could be achieved.

#### imported_Seer

##### Senior member
the most damage would be from your internal organs being pulled down at a weight of 3x that of what they were. We were talking about this in physics the other day when discussing the gravity on jupiter (~3g)

#### Matthias99

##### Diamond Member
Originally posted by: alpha88
I think the human body would not have a difficult time adjusting to a gravity of ~3g.

Here is why:

a) The body can withstand bursts of significantly more than 3g, so I'm confident things won't break over time.

b) The body can handle higher G for durations (minutes, hours) with no significant side effects.

This leads me to believe that since the body performs just fine for hours at higher gravity (with no signs that trouble is around the corner), then if exposed to higher gravity for longer durations (days,weeks) the body will continue to perform just fine, and after months and years, the body will make minor adaptations to the new gravity.

I expect that one would grow stronger bones and muscles. I'm not sure how the circulation system will change, but skeletal muscles should help keep blood from pooling at your feet.

Your logic needs some work. I'm not sure "b)" is really true at all (most people certainly do not hold up well under 3+Gs for any length of time), and the leap you made in "a)" (ie, high Gs are okay for short periods of time, so they'll also be okay for long periods of time) is completely nonsensical.

#### Alexstarfire

##### Senior member
I don't see why it's not possible to last your entire life in 3Gs. If you just slowly work your way up to 3Gs you would adapt to it. There is no reason why you shouldn't considering that everything has adapted to the gravity that we have here. We don't really even feel it anymore.

#### alcoholbob

##### Diamond Member
Being mentally able to adapt to it is different from your bodily functions being able to adapt to it. Just like the experiment where you slowly heat water around a frog until he boils to death; he has certainly mentaly adapted but he has physical constraints.

Your body is not genetically designed withstand those Gs. If the entire human race suddenly faced 3Gs, 99.9% of people would probably die from it eventually, and the strong that survive procreate and continue the "new" human race. That's evolution in action. Nobody "adapts" physically, its whoever was "built from birth" to withstand latent pressures that create the next generation.

#### Gibsons

##### Lifer
Originally posted by: Astrallite
Being mentally able to adapt to it is different from your bodily functions being able to adapt to it. Just like the experiment where you slowly heat water around a frog until he boils to death; he has certainly mentaly adapted but he has physical constraints.

Your body is not genetically designed withstand those Gs. If the entire human race suddenly faced 3Gs, 99.9% of people would probably die from it eventually, and the strong that survive procreate and continue the "new" human race. That's evolution in action. Nobody "adapts" physically, its whoever was "built from birth" to withstand latent pressures that create the next generation.

The fascia supporting them can be strengthened, their fibrous (collagen) content can be increased.

#### Nathelion

##### Senior member
Not all parts of the human body are platic; compare it to software and hardware. If we regard muscles as "software", they could undoubtedly grow stronger and adapt (although there would be a limit to this as well). The basic structure of certain internal organs, such as the aforementioned kidney and liver, and the brain, is not subject to change due to environmental influences, however. Such "hardware" may not be able to withstand the higher gees.

##### Member
I have a mass of 70Kg, which translates to 686 Newtons (if my physics memory has not failed me; F=MA and in the case of weight F=Mg).

So at 3g obviously this is 2058 Newtons, or equivalent to carrying another 140Kg on me.

That is the same as someone with a mass of 154lbs carrying an extra 308lbs.

You may be able to survive for some time (hours, days, weeks?) but have fun huging the floor.

A more reasonable gravitational/accelerational force woul be 1.25g.

#### Smilin

##### Diamond Member
There is more to it than simply weighing three times as much. A fat guy doesn't have his brain squished into the back of his skull when he lays down.

What if your kidneys were thrown into a centerfuge? Would they still continue to function properly? What about if the blood flow to them was significantly reduced? Heck, are red blood cells even being properly formed at the same rate?