# Spacesuits and magnetic boots. Why?



## Vertigo (Jul 23, 2015)

Okay am I being stupid here but why do we invariably have astronauts in sf clumping around the outside of their spaceships using magnetic boots? The space station is mostly made of aluminium; why would you use something heavy like iron for the shell of a space craft?


----------



## Ray McCarthy (Jul 23, 2015)

Stronger and maybe more shielding? Recycled nuclear submarines (they probably are spaceworthy!)
We can't afford to launch steel spaceships.  But a hypothetical future craft might be titanium / alumina ceramic / diamond / copper hybrid shell*, goo**, plastic, water then plastic or aluminium inner skin.

Actually it's a long time since I read a story with mag boots EVA. My SF EVA folk have tether lines and little gas thrusters to manoeuvre. No mag boots. Inside they rely on acceleration to create gravity effect.

Edit:
I think I read a story or several that had sort of velcro?

(* refractory, strong, spread heat. Diamond is very heat conductive, hard, refractory, electrical insulator. Titanium is compromise between Aluminium/Magnesium alloy and Steel)

(** Goo that sets if in vacuum etc to seal micrometorite holes.)


----------



## Brian G Turner (Jul 23, 2015)

Vertigo said:


> why do we invariably have astronauts in sf clumping around the outside of their spaceships using magnetic boots?



Presumably because "magnetic gravity" seems potentially more realistic than "artifical gravity".

In other words, there is no gravity - but iron walkways + magnetic boots, and you can at least stop your crew from floating uncontrollably through your starship.


----------



## Venusian Broon (Jul 23, 2015)

Isn't it just a woolly way for those filming SF to explain why, although their characters are in space and should be in freefall, they can't afford to show this? 

I don't remember the last time I read some SF that had this, but I seem to remember it in a few TV shows. It's in ST:TNG where Jean-luc blasts a few borgs off the top of the Enterprise and they had to use magnetic boots to go out to battle them (but surely they had artificial gravity just inside the hull on the decks, why couldn't they have 'extended' this to just outside the ship?)


----------



## Vertigo (Jul 23, 2015)

But why would you use iron, Brian? It's just such a heavy material to use.

Ray the example I mention was the ISS which is mostly aluminium so I guess they figure it provides sufficient shielding. I agree a Velcro approach is a workable solution on carpets or their equivalent and I've seen it used in quite a few sf stories.

So VB you'd agree that magnetic boots in space would likely be pretty useless? I've no idea why this question should have only just occurred to me, and I'm certain I have come across it in many sf books both old and new, not just in films.


----------



## Ray McCarthy (Jul 23, 2015)

You wouldn't use iron at all.
I'm not sure which is the lightest magnetic material for  magnetic boots to stick to, the walkway or shell. Some stainless steels are not magnetic.
Alinco may be lighter. I think the first modern magnetic material, an Aluminium, Nickel & Cobolt alloy.

Generally I think there are no light wieght materials  magnetic boots will stick to. But you'd not use iron.

The boots themselves would be the sort of rare earth alloy magnets in earbuds. It's not any advantage to make a walkway or shell from.


----------



## Vertigo (Jul 23, 2015)

I'm just surprised this has only just occurred to me, I'm usually very pedantic about this sort of thing.


----------



## Venusian Broon (Jul 23, 2015)

Vertigo said:


> But why would you use iron, Brian? It's just such a heavy material to use.
> 
> So VB you'd agree that magnetic boots in space would likely be pretty useless? I've no idea why this question should have only just occurred to me, and I'm certain I have come across it in many sf books both old and new, not just in films.



Yeah, given the non-magnetic nature of aluminium hulls, I'd agree that magnetic boots are pretty much useless. 

(_VB scurries away to check that's he's not written anything in his work that has this...uses very fancy artificial inertial fields instead, VB breaths a sigh of relief) 
_
When you mentioned it, it did seem like a well worn trope to me, but then I struggled to think of any book I've read that uses it. 


Perhaps as an alternative, you could charge the section of the hull you wanted with electrons, say, to give it an electric field then have a pair of boots that have a positive charged core (with heavy duty insulator around it to stop the charge equilibrating). So giving your astronaut some attractive forces on their feet. Possibly dangerous though - haven't done the sums on how much charge you'd need to give a reasonable force.


----------



## Ray McCarthy (Jul 23, 2015)

Venusian Broon said:


> charged core


sorry, won't work.
I know you can stick balloons to walls or paper to combs or anything insulated to front of many CRTs with Static Electricity. I'm fairly sure it won't scale up. Some kind of velcro will work better.


----------



## Venusian Broon (Jul 23, 2015)

Ray McCarthy said:


> sorry, won't work.
> I know you can stick balloons to walls or paper to combs or anything insulated to front of many CRTs with Static Electricity. I'm fairly sure it won't scale up. Some kind of velcro will work better.



Actually looking at it, I think it would scale up nicely and give you a strong force. The balloon example is a case in point - a pitifully few number of electrons is all it takes to counterbalance the full gravitational effect of all the particles in the Earth.

However I'm pretty sure it would be dangerous and cause all sorts of problems with your spaceship. So I agree that if you really must have to walk on the hull, a velcro sort of system would be better.

EDIT: Then again some sort of electrostatic field might also be good at stopping a whole range of harmful radiation penetrating the hull...

Found this interesting article: http://science.nasa.gov/science-news/science-at-nasa/2005/24jun_electrostatics/ 

Yes it's not a spaceship, but it's a nice application of some simple electrostatics.


----------



## BAYLOR (Jul 23, 2015)

Vertigo said:


> Okay am I being stupid here but why do we invariably have astronauts in sf clumping around the outside of their spaceships using magnetic boots? The space station is mostly made of aluminium; why would you use something heavy like iron for the shell of a space craft?



Because it's a science fiction movie, It looks cool, and it's the kind of mistake that the average person wouldn't even notice.

Truth be told I didn't think about that one until you brought it up. It's an interesting point .


----------



## chrispenycate (Jul 23, 2015)

How about neodymium boot soles and superconducting coils in the hull metal with continuously circulating current as screening against charged particles?


----------



## Ray McCarthy (Jul 23, 2015)

Venusian Broon said:


> some simple electrostatics.


A folded to 1cm piece of aluminium foil strip (about 2cm x 3mm)  in a jam-jar (or any glass jar) suspended across the top by plastic cocktail stick. Makes a demo Electroscope for the kids to compare charges.

The two leaves of the fold repel and open it further the stronger the charge as the excess electrons (-) or lack of electrons (+) repel the two leaves. (+ or - works).


----------



## Ray McCarthy (Jul 23, 2015)

chrispenycate said:


> neodymium boot soles and superconducting coils


Don't need the superconducting coils as the neodymium are magnets, so no second magnet needed. Just ferromagnetic material skin.


----------



## TheDustyZebra (Jul 23, 2015)

BAYLOR said:


> Because it's a science fiction movie, It looks cool, and it's the kind of mistake that the average person wouldn't even notice.
> 
> Truth be told I didn't think about that one until you brought it up. It's an interesting point .



I didn't, either. It would not have occurred to me that the space station or any other space installation was aluminum -- seems like it would be too flimsy in case of meteorites (or whatever they're called in space). But of course, now it will bug me. Thanks a lot.


----------



## Ray McCarthy (Jul 23, 2015)

@TheDustyZebra 
A meteorite will zip through steel anyway. Radiation isn't a huge issue (unless in daylight and massive solar flare). We can't afford to ship case /shells heavier than Aluminium. Inflatable plastic is under serious consideration.


----------



## chrispenycate (Jul 24, 2015)

Ray McCarthy said:


> Don't need the superconducting coils as the neodymium are magnets, so no second magnet needed. Just ferromagnetic material skin.


But I wanted the deflection fields anyway.

All this assumes spaceships are built on Earth, or at least the prefabricated bits are shipped up from Earth. If we had a decent size nickel/iron asteroid floated into Earth orbit for raw material, ferromagnetics might be the cheapest solution for building hulls. A bit slower to accelerate, but an ion drive's hardly going to do Ferrari smoking tyres at the best of time:- 0-60 in fifteen hours and a few seconds.


----------



## Ray McCarthy (Jul 24, 2015)

chrispenycate said:


> but an ion drive's hardly going to do Ferrari smoking tyres at the best of time


Unless it's got an 8km long linear accelerator and multiple Fusion power sources


----------



## TØny Hine (Jul 24, 2015)

I think suction pads would be better.


----------



## Ray McCarthy (Jul 24, 2015)

TØny Hine said:


> suction pads


I'm not sure they work in a vacuum.

EDIT:
My suspicion as to how they work is correct.
https://en.wikipedia.org/wiki/Suction_cup

They will work inside the pressurised section.


----------



## Brian G Turner (Jul 24, 2015)

Vertigo said:


> But why would you use iron, Brian? It's just such a heavy material to use.



True, I meant any conducting material, and iron was the first thing that came to mind. I should have thought more carefully before posting.


----------



## Vertigo (Jul 24, 2015)

I'd wondered about suction pads, but I'm sure Ray is right that suction pads work using atmospheric pressure.



BAYLOR said:


> Because it's a science fiction movie, It looks cool, and it's the kind of mistake that the average person wouldn't even notice.
> 
> Truth be told I didn't think about that one until you brought it up. It's an interesting point .


To be fair I wasn't just thinking of movies, I have come across it often enough in books as well.



chrispenycate said:


> But I wanted the deflection fields anyway.
> 
> All this assumes spaceships are built on Earth, or at least the prefabricated bits are shipped up from Earth. If we had a decent size nickel/iron asteroid floated into Earth orbit for raw material, ferromagnetics might be the cheapest solution for building hulls. A bit slower to accelerate, but an ion drive's hardly going to do Ferrari smoking tyres at the best of time:- 0-60 in fifteen hours and a few seconds.


I still think the extra weight, and therefore inertia would make heavy metals impractical at least you wouldn't do it just to make it easy to walk on the hull. Though some interaction with an EM field for shielding does seem a possibility.



TheDustyZebra said:


> But of course, now it will bug me. Thanks a lot.


Sorry but it'll bug me too if that's any compensation! 

It's interesting to think of solutions, though that wasn't really my initial question; I was just trying to figure out what I'd missed and it looks like I hadn't missed anything. On the solution front, I think the simplest solution is that we wouldn't bother and instead would use safety lines and manoeuvre using some of compressed gas 'jets.' The safety lines wouldn't be a huge nuisance as they could be self-releasing and in pairs on reels; clip second one and release and reel in first one and so on.


----------



## Ray McCarthy (Jul 24, 2015)

Brian Turner said:


> I meant any conducting material


Magnetic Material. Loads of conductive materials don't work (tin, brass, bronze, aluminium, magnesium, copper, lead, silver, gold, platinum). While steel generally works, some steels (particularly some but not all "inox" / "stainless") mysteriously don't work with magnets.

I find Magnets, Static Electricity, electro-magnetism, flowing electricity, high voltages, Electromagnetic waves (LW, SW, VHF, UHF, Microwave, IR, Light, UV and the differing properties) all fascinating to read about and do experiments with. Pairs of polarisers, home made waveguides and transitions for 2.4GHz and  10GHz, Log Periodic aerials, phased aerial arrays, parabolic dish variations etc ...

I bought a load of €1.50 "quartz" clocks to experiment with the miniature 1V driven actuator coils. A little electromagnet pokes the second hand cog once a second, driven by IC chip which is dividing a miniature quartz (glass) tuning fork with two silvered contacts so that piezo electric power keeps the fork oscillating at 32768 times a second. This is divided by 2 fifteen times to give the 1 second pulses. Same "crystal" as used in many LCD watches.  Higher frequency quartz crystals are just small wafers using piezo effect to sustain the physical vibrations. An old record player crystal or ceramic cartridge (or gas lighter with no battery) uses piezo effect in reverse to make electricity. The speaker in a tune playing greeting card is a piezo ceramic disc mounted on brass disc.


----------

