Some random questions about space travel

[Algiark]

1. Can airlock and docking port be a single part?

2. How good is a grappling hook gun to move around in space?

3. Why don't spacesuits have a flexible neck?

4. Why is the ISS made of cylinder shapes, instead of boxes?

5. How far can you get from the sun until solar panels aren't practical anymore?

6. And what determines the practicality of solar panels?

7. Related to the ISS question, why do realistic spaceship concepts look... the way they do? Long pipes with stuff attached to it?

 

 

[magnemoe]

1 problem is that most docking ports are too narrow to pass trough easy in an eva suit, it would not work with an MMU / jetpack unit. 
If you dock something you could not use it as an airlock anymore
Better to have an dedicated one, perhaps have one port as an emergency airlock 

2 not much, it has to grab something who don't breaks and it might easy come loose if no pressure on it. 

3 Flexible joints in spacesuits are hard, they are also stiff, better to use an larger helmet. it would be lighter than an flexible one. 

4 cylinders fit into fairings and the shuttle cargo bay, they are also easier to make airtight. 

5 Juno use them out at Jupiter. More an issue that effect drops off with distance, 

[kerbiloid]

33 minutes ago, Algiark said:

1. Can airlock and docking port be a single part?

An IRL single part. But with 4 different holes: airlock (top), docking port (rear), torpedo capsule launcher (bottom), front (doorway to home).

Spoiler

 

33 minutes ago, Algiark said:

2. How good is a grappling hook gun to move around in space?

If you miss, it will ricochet and hit you.
If you hit the target, it will pierce it.

33 minutes ago, Algiark said:

3. Why don't spacesuits have a flexible neck?

Because a pressurized suit is a can with a human inside, and its head doesn't need to rotate, while unpressurized but tight (making pressure not by gas, but by rubbers) will smother the owner.

33 minutes ago, Algiark said:

4. Why is the ISS made of cylinder shapes, instead of boxes?

Because a flat wall must be thicker for the same pressure.

33 minutes ago, Algiark said:

5. How far can you get from the sun until solar panels aren't practical anymore?

Afaik, Saturn is the outer limit.

33 minutes ago, Algiark said:

6. And what determines the practicality of solar panels?

They need no fuel, produce no waste or heat, require no engineer to keep them intact, make no problem when a probe explodes in the atmosphere.

33 minutes ago, Algiark said:

7. Related to the ISS question, why do realistic spaceship concepts look... the way they do? Long pipes with stuff attached to it?

They are space favela. Made of tin and random shaped.

Edited November 11, 2016 by kerbiloid

[peadar1987]

4. Among other reasons, not least of which is that cargo bays of launch vehicles are usually cylindrical, cylinders are better at holding pressure. In general, corners are not good in space. Stress tends to concentrate at corners and other sharp changes in shape. A cylinder or other smooth profile is best, as it gives nowhere for stresses to build up. A cylinder would be even better, but they don't pack into cargo bays as easily or tightly, so don't get used so much.

[p1t1o]

2 – As far as I know, grappling hook guns are not a thing. Its all well and good firing a hook over a ledge, but its not guaranteed to catch. And if it does catch, how do you know it will hold your weight?

In space you’d have 3 problems, first, firing the gun (any gun) if you are floating freely, would give you an unwanted impulse, which will propel you away from your target, but much worse it may send you tumbling, and you may not have a way to stop.

Second, you reallllllly don’t want your hooked projectile to puncture anything.

3rdly, say you fire a hooked cable at something and it catches – when you reel yourself in, you maintain the same angular momentum relative to the destination, and just as the ballerina speeds up when she brings her arms and legs closer to her centre of mass, you will rotate around your target faster and faster as you approach, this can easily lead to you being smacked very hard into something, or even being flung into space.

Oh and a hook isnt going to be much use in space, they tend to rely on gravity to catch on anything, so you'd need a kind of "universal" grabby bit, a blob of adhesive might be a good bet, but that has its own problems.

No I don’t think any sort of “gun” would be a great way to move around in space.

4 – The same reason that when you inflate a balloon, it doesn’t become a cube.

[kerbiloid]

54 minutes ago, p1t1o said:

4 – The same reason that when you inflate a balloon, it doesn’t become a cube.

= Because modules are bubbles, and bubbles are round.

[DrLicor]

For as far as it hasn't been answered, here are mine:

1. Can airlock and docking port be a single part?
Yes is can, but not practical. Dockingports are mainly used for docking the crafts. So when people are passing through a docking port, they have no spacesuits on. It would be non practical to make every dockingport that big.

2. How good is a grappling hook gun to move around in space?
Depends, since there isn't any (almost) resistance/friction in space from air. It will be slightly more powerfull. It doesn't lose any speed. However, this will only noticeable with pretty large hooks.

3. Why don't spacesuits have a flexible neck?
Because it's easier. It's not like a motor helmet you put on, you have make sure it doesn't lose pressure. a flexiable neck would make it more complicated to realise.

 4. Why is the ISS made of cylinder shapes, instead of boxes?
Has nothing to do with the rocketshape or something like that, if would want boxshaped parts, they could make the rocket boxshaped too. Instead it has to do with pressure. The same reason why soda cans are cylindershaped too. When apply pressure to a cylinder, the cylinders outside has the same pressure on every spot. (not top and bottom) Thats because the distance from centre of the cylinder to a random spot is the same. The best way, so you you have to use less resources, is to make everything a sphere.
Here's an explanation: http://canyouactually.com/heres-why-the-soda-can-is-shaped-the-way-it-is-and-its-absolutely-fascinating/

5. How far can you get from the sun until solar panels aren't practical anymore?
Again, it depens on your solar panel. i don't know the precise distance, but with technology, that distance is getting bigger and bigger. 

6. And what determines the practicality of solar panels?
It's free energy what you get. And almost the only energy you can get in space. You can't just place a powerplant in space to produce energy. Another way to make energy in space is with fuel, but that is way more expensive. You don't want to bring extra full to the space station for keeping up the power. (besides the fuel need for altitude control) Solar panels require little maintenance. After installation and optimization they are very reliable due to the fact that they actively create electricity in just a few millimeters and do not require any type of mechanical parts that can fail. And it's clean. 

7. Related to the ISS question, why do realistic spaceship concepts look... the way they do? Long pipes with stuff attached to it?
Again, practical reasons. If you make for some reason a sphere space station, you don't use the whole room/space, so you are throwing away the energy to keep it pressurised and warm. However, it is possible to construct those pipes side to side. I don't know the reason why they didn't do that, I don't know why they should. Also, remember you can only construct things made of small thing. You need to launch it in space and can't just launch a 50meter sphere. Unless it's inflatable. Which is an upcoming thing now. 
https://en.wikipedia.org/wiki/Bigelow_Expandable_Activity_Module

 

[Ten Key]

7 hours ago, Algiark said:

4. Why is the ISS made of cylinder shapes, instead of boxes?

As others have mentioned, cylinders are much better at resisting pressure differentials. Submarines have cylindrical pressure hulls for the same reason. 

[mikegarrison]

Sharp corners are bad for stress. The sharper they are, the worse they are. The shape with the least-sharp corners is a sphere, but a tube is also pretty good except at the ends.

What no one has specifically mentioned yet is that reducing stress means you can reduce the strength of the part, which means you can reduce the weight of the part. And that's why airplane and spacecraft pressure vessels usually look like they do -- because it saves weight to make them that way.

[kerbiloid]

Though the topic is about Near future, the ideally shaped spacecrafts of Far future are:

Spoiler

 

 

 

Spoiler

Not a Death Star because its shape is very inefficient for inertial and inner space distribution reason.

 

 

Edited November 12, 2016 by kerbiloid

[radonek]

On Friday November 11, 2016 at 1:33 PM, DrLicor said:

However, it is possible to construct those pipes side to side. I don't know the reason why they didn't do that

Because that would require more structural mass. For most spaceships, strongest forces comes from its own propulsion. If you stack everything on top of propulsion unit, in axis of thrust, structure undergoes only pressure stress. Structural materials handle that pretty well. Radial mass imparts additional torque stress which is harder to handle. (hint: is it easier to break a stick by pushing ends or bending it?)

Other reasons why spacecrafts tend to be elongated is that RCS is more efficient that way. And if spacecraft carries nuclear reactor, it is more efficient to limit exposure by having crew farther away and behind small shadow shield then carrying very, very heavy radiation shielding.
 

[YNM]

On 11/11/2016 at 4:39 PM, Algiark said:

1. Can airlock and docking port be a single part?

2. How good is a grappling hook gun to move around in space?

3. Why don't spacesuits have a flexible neck?

4. Why is the ISS made of cylinder shapes, instead of boxes?

5. How far can you get from the sun until solar panels aren't practical anymore?

6. And what determines the practicality of solar panels?

7. Related to the ISS question, why do realistic spaceship concepts look... the way they do? Long pipes with stuff attached to it?

1. They already do - just add another "door" so the room before last "door" (dock/airlock) can be depressurized / re-pressurized, or you'd need to press-depress the whole station/room, which is impractical. Though, as has been stated before, it's not that practical compared to having dedicated airlocks.

2. Not very well I supppose - most things in space are smooth, unless we're talking about grappling a massive rock or trusses.

3. Helmets. Also, our necks are pretty short. Unless you have giraffe as astronauts I don't imagine we need one.

4. The same thing why most industrial tanks w/ pressurized gasses in them are cylindrical / spherical. Our breathing atmosphere would be considered super-high-pressure compared to space vacuum.

5. Roughly around Jupiter distance, with current PV efficiency figures.

6. Output it generates vs it's weight and size, which are mainly dictated by distance from the Sun and the panel's efficiency, as well as mass density.

6. Because it's cylinder (big pipes) with external cylinders (long pipes) attached to it. Surely you can't live in a bare truss segment, nor that you'd want to pressurize a box.

Edited November 13, 2016 by YNM

[kerbiloid]

15 hours ago, radonek said:

Other reasons why spacecrafts tend to be elongated is that RCS is more efficient that way.

RCS is more efficient when RCS arm is elongated, not a spacecraft. Moment of force ~ Force * Arm
The greater a spacecraft is elongated, the greater its angular inertia. Moment of inertia ~ Mass * Size
The greater is inertia, the less efficient is RCS. Angular acceleration =  Moment of force / Moment of inertia.

So, elongated ships are the worst from the RCS pov. Compact ships with RCS on long trusses are the best.

OS Mir with RCS truss "Sophora" (the upper one).
(The lesser one is "Rapana", with scientific instruments)

Spoiler

 

[NSEP]

Do you peeps mind if i ask some questions too?

8. What materials are fuel tanks made of?

9. Why are fuel tanks not reflective like a mirror to reflect of all the sunlight? Should that not keep the temprature normal?

[radonek]

44 minutes ago, NSEP said:

What materials are fuel tanks made of?

Hydrazine tanks are made of steel or  titanium alloys, since it resists corrosion.  LoX/LH tanks are usually from some light aluminium alloy.

 

[kerbiloid]

20 hours ago, NSEP said:

8. What materials are fuel tanks made of?

Al-Mg, Al-Li alloys.

20 hours ago, NSEP said:

9. Why are fuel tanks not reflective like a mirror to reflect of all the sunlight? Should that not keep the temprature normal?

Inside they are.

Edited November 14, 2016 by kerbiloid

[p1t1o]

21 hours ago, NSEP said:

9. Why are fuel tanks not reflective like a mirror to reflect of all the sunlight? Should that not keep the temprature normal?

You might notice a lot of rockets are white. Generally speaking, matt white surfaces are actually a lot more reflective than mirrored surfaces, it is just that the light is scattered so you dont see a reflected image, but it looks white from every angle due to the large amount of light being reflected/scattered. Why do they use metalised foils and things as space insulation? Probably because its very thin and light.

Another examples is the "anti-flash white" that nuclear bombers used to use back when high-altitude missions were the norm:

http://colors.findthedata.com/l/835/Anti-Flash-White

Fun Fact - this would also apply to sci-fi "anti laser armour", so when your book talks about "mirror armour" or somesuch, it is a bit of a blunder. Not only would matt white reflect more energy, but a literal mirror would not de-focus the beam, so on reflection it could strike another target.

 

Edited November 14, 2016 by p1t1o

[magnemoe]

1 hour ago, p1t1o said:

You might notice a lot of rockets are white. Generally speaking, matt white surfaces are actually a lot more reflective than mirrored surfaces, it is just that the light is scattered so you dont see a reflected image, but it looks white from every angle due to the large amount of light being reflected/scattered. Why do they use metalised foils and things as space insulation? Probably because its very thin and light.

Another examples is the "anti-flash white" that nuclear bombers used to use back when high-altitude missions were the norm:

http://colors.findthedata.com/l/835/Anti-Flash-White

Fun Fact - this would also apply to sci-fi "anti laser armour", so when your book talks about "mirror armour" or somesuch, it is a bit of a blunder. Not only would matt white reflect more energy, but a literal mirror would not de-focus the beam, so on reflection it could strike another target.

 

Against lasers white would also have another benefit, should be pretty easy to make an white ablative material who would continue to be white while boiling of.
An mirrored surface like polished steel would be burned black pretty soon and then absorb much more energy. 

[kerbiloid]

Let me throw a shovel more into the fan.

Warheads are black.

P.S.
ICBM designated as "Satan" is black, too.

Spoiler

 

 

 

Edited November 14, 2016 by kerbiloid

[p1t1o]

11 minutes ago, kerbiloid said:

Let me throw a shovel more into the fan.

Warheads are black.

P.S.
ICBM designated as "Satan" is black, too.

  Reveal hidden contents

 

 

 

The main body: Solid fuelled, not sensitive to solar heating.

The RV: Black is a good colour for a heatshield specifically because it has opposite properties to white - physical law says that good reflectors are poor emitters and vice/versa, black materials tend to radiate more readily than bright, reflective materials. However, most of the heat protection (in ablative heatshields of this type) comes from the layer of gas produced by the pyrolising heatshield material (essentially plastic) which insulates the RV against the extremely hot shockwave, and also carries the heat away with it - protection from radiative heating is a less significant concern in this case. Especially since the heatshield only had to work for a few minutes, whereas a civilian rocket full of cryogenic liquids might be sitting on a pad for hours.

It is of course possible that any vehicle/object could be painted any colour if radiative absorption/emission of heat is dealt with in another way, or is just deemed insignificant relative to other factors.

 

[kerbiloid]

5 minutes ago, p1t1o said:

The main body: Solid fuelled, not sensitive to solar heating

Not sure what do you mean as "main body"

[Ten Key]

3 hours ago, p1t1o said:

You might notice a lot of rockets are white. Generally speaking, matt white surfaces are actually a lot more reflective than mirrored surfaces, it is just that the light is scattered so you dont see a reflected image, but it looks white from every angle due to the large amount of light being reflected/scattered. Why do they use metalised foils and things as space insulation? Probably because its very thin and light.

Another examples is the "anti-flash white" that nuclear bombers used to use back when high-altitude missions were the norm:

Concorde was also painted white for thermal control.   https://en.wikipedia.org/wiki/Concorde#Heating_problems

Quote

Concorde had livery restrictions; the majority of the surface had to be covered with a highly reflective white paint to avoid overheating the aluminium structure due to heating effects from supersonic flight at Mach 2. The white finish reduced the skin temperature by 6 to 11 degrees Celsius. In 1996, Air France briefly painted F-BTSD in a predominantly blue livery, with the exception of the wings, in a promotional deal with Pepsi.[96] In this paint scheme, Air France was advised to remain at Mach 2 for no more than 20 minutes at a time, but there was no restriction at speeds under Mach 1.7. F-BTSD was used because it was not scheduled for any long flights that required extended Mach 2 operations.

The foiled insulation on spacecraft is basically a blanket-- it's designed to both retain heat and reflect it. 

[kerbiloid]

Also, LGM-118 is black.

Spoiler

They are black because of carbon plastic. It has high heat capacity and low heat conductivity

Edited November 14, 2016 by kerbiloid

[p1t1o]

15 hours ago, kerbiloid said:

Not sure what do you mean as "main body"

Was referring to the "fuselage", modern ICBMs are solid-fuelled, or at the very least have done away with cryogenic fuels (in order to keep response time down) so thermal control via paint colour is less important.

[kerbiloid]

3 hours ago, p1t1o said:

Was referring to the "fuselage", modern ICBMs are solid-fuelled, or at the very least have done away with cryogenic fuels (in order to keep response time down) so thermal control via paint colour is less important.

R-36 aka Satan is liquid hypergolic, not solid, but I got your idea.