News We probably won't be going to Mars anytime soon.

[Hlynkacg]

Well for one difference between centrifugal gravity and mass gravity.. you have no torque.

With the torque removed when you return to earth.. You might walk lopsided and kinked for a while!

1: That assumes that you will be returning to earth in the first place.

2: It comes right back to the fact that the engineering tolerances for torque and other forces on the human body are easily testable.

In either case, the argument that we can't do long term space travel because we don't have the technology to compress a planet sized mass into a manageable volume is so farcical that it barely warrants a response.

 

[kamaz]

What I am talking about is physiological damage: Do
we know for a fact that centrifugal force OVER EXTENDED.
PERIODS (6 months say) causes no harm to tissues/cells.
For a Station the radius of 300m ( Size of wheel in film2001 Spc Odys. for Example.)

If you are committed to building a Mars stack, the mission to verify that can be put together pretty quickly: launch a hab connected by a 300m tether to a counterweight into LEO. Send a crew up on Orion, keep it in space for 6 months, return it, check the health state. A typical Mars program schedule runs 10-20 years anyway, so a year of delay is not going to be a catastrophe.

Seriously, these kind of arguments seem to be raised by people who want to not go to Mars and are looking for excuses.

 

[Loru]

You know we assume centrifugal force is a good substitute for gravity.

Long enough tether (to minimize torque and gravity gradient) makes it identical to gravity achieved by other means (accelerating vessel at 1g, being stationary in gravity field of a planet or having convinient small black hole strapped under your ship's floor ).

For human being it does not matter how it's achieved. What counts is acceleration in proper direction, magnitude and gradient. We know this as [ame="http://en.wikipedia.org/wiki/Equivalence_principle"]equivalence principle[/ame] .

---------- Post added at 09:52 PM ---------- Previous post was at 09:46 PM ----------

As for prolonged exposure (Space odyssey type station):

Your body is at almost constant movement every second. Each time you lean in your seat, breathe, move your head, walk and generally do stuff, parts of your body experience accelerations in different directions. Sailors at sea have it much harder than little bit of torque at 300 meter in radius centrifuge.

 

[Admiral_Ritt]

1: In either case, the argument that we can't do long term space travel because we don't have the technology to compress a planet sized mass into a manageable volume is so farcical that it barely warrants a response.

Easily Testable, WITH AN ACTUAL STATION: This visual acuity problem
astronauts experienced, did anybody anticipate or pre-test for that ON EARTH?

You want to throw FARCE at me: go ahead,
But all of these technologies to create artificial enviroments
have to work w/o side effects.

I was giving a hypothetical example were a technical barrier may
not have a tractable solution, and thus can become a show stopper.

 

[Hlynkacg]

Easily Testable, WITH AN ACTUAL STATION: This visual acuity problem astronauts experienced, did anybody anticipate or pre-test for that ON EARTH?

Or a merry-go-round...

Trorque gradients are trivially easy to reproduce here on earth.

The visual acuity problem is a direct result of exposure to micro gravity, specifically increased pressure on the optic nerve due to the fact that blood and CSF does not drain from the eye or the area surrounding it as it normally would.

You want to throw FARCE at me: go ahead,
But all of these technologies to create artificial enviroments
have to work w/o side effects.

No they don't. The side effects just need to be manageable.

You also have yet to explain how gravity derived from mass is different from gravity derived from acceleration.

 

[kamaz]

You want to throw FARCE at me: go ahead,
But all of these technologies to create artificial enviroments
have to work w/o side effects.

Nope. They have to work with acceptable side effects.

In many professions, risk of occupation-caused disability or death is quite high, yet deemed to be acceptable (as people wouldn't take these jobs otherwise). And these jobs pay much less than being a career astronaut!

 

[Admiral_Ritt]

Nope. They have to work with acceptable side effects.

For Decades in duration/effect in an interstellar voyage.?

 

[Hlynkacg]

For Decades in duration/effect in an interstellar voyage?

Yup.

If the side-effects can be mitigated or are otherwise deemed acceptable by those making the voyage, duration becomes largely irrelevant except for calculating logistics.

 

[Loru]

For Decades in duration/effect in an interstellar voyage.?

Are you concerned about this minimal torque in case of 300 meter centrifuge?
Solution: sleep one day in one direction and other day in oposite.

Gravity gradient at this radius is minimal and forces on your body are smaller than streching you do after you wake up.

 

[MikeB]

We talk about centrifugal force, but I seldom see anything about coriolis forces in a rotating spacecraft. An effective "1-g" of centrifugal force can be achieved with a variety of radius and rotation rate, but I suppose they would all "feel" different due to coriolis effects. For instance, the path of a dropped object will be curved anti-spinward. Does anyone have a feel for how this would affect an "optimal" (in whatever sense you wish to propose) arrangement? Have any tests been done?

 

[kamaz]

For Decades in duration/effect in an interstellar voyage.?

Moving goalposts. First, interstellar voyage is not the subject of the thread. Second, if your ancestors were thinking like you are, they'd be still in Mesopotamia trying to design a 747 instead of using a boat.

Besides, non-relativistic interstellar voyage is a dumb idea. See Orphans of the sky or Wall-E.

 

[RGClark]

Why would gravity require physical mass? Why not 9.81 m/s^2 of acceleration?

Likewise the causes of micro gravity's physiological effects are fairly well understood. Basically it comes down to atrophy and the fact that is no longer flowing down-hill.

The problem here for linear acceleration is the engine would be firing continually over the entire distance and I think this would turn out to have too small an acceleration to have a useful effect.

Bob Clark

 

[Hlynkacg]

That's not actually a problem because 1: centrifugal force works. and 2: brachistochrone trajectories to Mars are within our theoretical capability, even if we will never actually do it because (as this thread illustrates) people tend to be freak out about any and every thing involving radiation and nuclear power.

 

[RGClark]

Further on the radiation dangers of a Mars mission:

Cosmic ray radiation could prevent humans from travelling to Mars.
3 DAYS AGO APRIL 25, 2014 8:57AM

Cucinotta estimates that, as technology currently stands, an astronaut’s lifespan would be shortened by 15-24 years by a trip to the red planet.
http://www.news.com.au/technology/s...avelling-to-mars/story-fnjwlcze-1226895669558

Why I say we need to do short travel times to Mars such as by plasma propulsion.
At the Humans to 2 Mars conference the focus was on solar electric propulsion as an enabling technology. Recent advances suggest we currently have the capacity to produce such a mission.


Bob Clark