Question about machines in space

[Dari]

Why is it that a lot of machines (satellites, space station, hubble telescopes, etc...) that go into space seem as if they're built to survive in a vacuum and not in the harsh conditions of space? For example, if you look at any satellite or the space station, it is easy to identify weak points (e.g. the joints, or mirrors). How is it that these points stand up to the harsh environment of space (extreme temperature, space debris travelling at 20k mph)?

For example, look at this machine:

How are those panels able to withstand the extreme environment of space without getting destroyed? Also, if you look at the joints, they don't look all that secure.

Or this:

How are those panels able to withstand debris travelling 26X the speed of sound? How are the joints able to withstand the elements?

 

[96Firebird]

The joints don't need to withstand debris, as the things they are supporting are fragile enough. It won't matter if the joint can withstand the object if the panel the object is supporting will shatter anyways.

 

[sunzt]

they're designed to withstand debris that are usually under 10 cm diameter, which accounts for most space debris. You don't design a ford focus to withstand a missile (asteroid). Also, the joints are not constantly moving much. The solar arrays will be able to tilt some degree, but that's it. If an external force hits a solar array it's going to rotate the whole body rather than shear off the joint. So having an adequate GNC system is important to counter any perturbations. You can design your structures to withstand heat and cold with proper thermal control.

The most consistent threat in space is ionizing and non-ionizing radiation because those are guaranteed to occur, where as a collision with an object >10cm diameter is very rare.

 

[ichy]

Building something to withstand a collision with a big piece of space debris is impossible so there's no point in even trying.

 

[Dari]

Building something to withstand a collision with a big piece of space debris is impossible so there's no point in even trying.

Size is not an issue here. It's the speed and temperature that is an issue. Something travelling at 20k mph, even if very small, can do a lot of damage.

 

[diesbudt]

Size is not an issue here. It's the speed and temperature that is an issue. Something travelling at 20k mph, even if very small, can do a lot of damage.

Temperature is not an issue. Most machines actually work more efficiently (and even electricity) in much colder temperatures.

The only issues in space is debirs, and radiation.

As pointed out majority of space debris the machine is built to take.

The real issue as also pointed out is radiation from the sun. Solar flares could seriously damage the satellites.

 

[Number1]

Cars on earth are built to withstand weather extremes and wind pressure on the highways. They are not made to withstand bullets or being hit by other objects. Same for spacecrafts. They are built to operate in the vacuum of space and to endure extreme temperatures and radiation.

 

[xBiffx]

Temperature is not an issue. Most machines actually work more efficiently (and even electricity) in much colder temperatures.

Where did you come up with that nugget of bs? Robotics, in particular, motors start failing to work before you even reach -80C. Cold is very, very bad for many electro-mechanical devices.

As to the OP. Other than temperature fluctuations and collisions with debris, which you can't engineer around due to the sheer numbers (speed, mass, quantity) involved, conditions in space are not harsh at all. This is part of the reason why the astronauts during the Apollo mission sometimes had merely a few layers of foil protecting them from space and there weren't any major issues because of it.

 

[Fritzo]

Space designs are thin and redundant. The panels may be easily punctured with little damage, and the core section is heavily insulated which provides shielding.

 

[Dari]

So, what you guys are saying is that, with the exception of radiation, if it happens it's either so rare that we don't need to prepare for it or that it'll be so damaging that we cannot prepare for it. Either way, there is no need to prepare for it.

 

[moonbogg]

You can design moving parts with thermal expansion of materials in mind to prevent binding. Mechanical joints in space don't need to support any weight, only the resulting inertial forces from the very slow movements that are employed for fine tuning and adjustments made to panels. If the same panel was used on earth, the joint would be much more robust to resist gravity. I'm a designer, not an engineer. This is just common sense stuff.
Regarding radiation, I have no clue. I heard it can be kind of bad and needs to be planned for?

 

[dighn]

So, what you guys are saying is that, with the exception of radiation, if it happens it's either so rare that we don't need to prepare for it or that it'll be so damaging that we cannot prepare for it. Either way, there is no need to prepare for it.

and cost of sending mass into orbit is very high. putting armor on everything would be prohibitively expensive. making things thin also reduces chance of collision.

 

[sunzt]

and cost of sending mass into orbit is very high. putting armor on everything would be prohibitively expensive. making things thin also reduces chance of collision.

That's why satellite constellations always have backup satellites in case one goes down.

 

[yottabit]

You also believe it or not can run into overheating issues in space. Basically in the absence of air you lose the heat transfer mechanism of conduction (and convection), which is extraordinarily effective. So you are stuck with only radiation heat transfer. Your Hyper 212+ in the abcense of air would have probably 1/10th the cooling capacity

 

[Paratus]

For the ISS:

The pressurized modules can with stand small impacts from orbital debris. The hull is two layers thick. The first layer causes the incoming debris to vaporize which spreads itself out before hitting the inner layer.

Larger debris is tracked by radar and we perform a debris avoidance maneuver if there's enough time.

Debris that could puncture the hull buts too small to pickup on radar we have procedures in place to mitigate damage or at least protect the crew. We know how big a hole the debris could make so we know how much time it would take the stack to decompress. In the worst case the crew would leave in the Soyuz.

For the exterior parts of the station, the solar arrays are designed such that a hole in one cell only stops a small number of adjacent cells from functioning limiting the damage.

The large radiators have multiple independent fluid lines in them that can be isolated if debris punches a hole in one.

The smaller radiators that cool the power equipment on the solar arrays don't have that redundancy and in fact we are going to have an EVA in a couple of days to fix a slow leak in one of them.

Thermal issues are a huge pain for the ISS. Basically anytime we maneuver large number of thermal analysis need to be performed to make sure we don't over or under temp anything.

Most boxes inside an out have spares and can be replaced with some difficulty. We actually just replaced one during 2 EVAs a couple of weeks ago.

For radiation. The command and control computers are a combo of pentiums or 386s which are more resistance to single event upsets due to high energy particles. (Crew laptops are more recent think pads)

The crew are treated like radiation workers and their life time exposure is calculated. If you're bumping up against the limit you don't fly again.

<-- works in mission control

 

[Paratus]

Better picture:

 

[dave_the_nerd]

putting armor on everything would be prohibitively expensive.

Even if it would be FREAKING AWESOME. :awe:

 

[Pulsar]

Temperature is not an issue. Most machines actually work more efficiently (and even electricity) in much colder temperatures.

The only issues in space is debirs, and radiation.

As pointed out majority of space debris the machine is built to take.

The real issue as also pointed out is radiation from the sun. Solar flares could seriously damage the satellites.

If you're going to be retarded, at least don't post it out in the open for everyone to see.

The international space station sees extremes in temperature from 250 degrees F to -250 degrees F. That's just between the two sides of the space station, while in sight of the sun.

In fact, heat is always an issue. The radiation insulation to protect the astronauts also traps the heat in the station, and because convection doesn't exist in space they have to use heat exchangers that excel at radiation to remove all the waste heat.

One of the absolutely biggest design problems on the space station is keeping the whole damn thing sealed up while it's fluctuating +/- 250 F.

Hell, we struggle to calibrate our instruments using a 200mm ceramic bar. Just holding the bar too long while align it will throw it out on the under of 5-10 microns, even with coolant running.

 

[BUTCH1]

Your forgetting that there is no air in space, that's why things that look"flimsy" do just fine, 20K MPH, 40K MPH is irrelevant, there is no wind resistance because there is no air..

 

[ichy]

You also believe it or not can run into overheating issues in space. Basically in the absence of air you lose the heat transfer mechanism of conduction, which is extraordinarily effective. So you are stuck with only radiation heat transfer. Your Hyper 212+ in the abcense of air would have probably 1/10th the cooling capacity

You beat me to it. Air cooled electronics are problematic in space. In one shuttle astronaut biography the author stated very clearly that part of the reason they could never depressurize the entire shuttle cabin was the air-cooled electronics would overheat.

The Russians had the same issue with their first spacewalk. When the US did spacewalks from Gemini and Apollo spacecraft the entire cabin was depressurized so there was no need for an airlock. The Russians used more primitive air cooled electronics on the Voskhod capsules (I'm not sure how they did it on Soyuz) so when Alexei Leonov did his first space walk he needed a rather clumsy inflatable airlock. Depressurizing the cabin would've caused the electronics to get too hot.

 

[ichy]

Temperature is not an issue. Most machines actually work more efficiently (and even electricity) in much colder temperatures.

The only issues in space is debirs, and radiation.

Do a quick google search for the contingency checklists and procedures that shuttles used to use. Aside from engine failures and a loss of cabin pressure the partial or complete failure of the cooling system was probably the most serious problem that they trained for. Temperature is a HUGE issue.

 

[Paratus]

If you're going to be retarded, at least don't post it out in the open for everyone to see.

The international space station sees extremes in temperature from 250 degrees F to -250 degrees F. That's just between the two sides of the space station, while in sight of the sun.

In fact, heat is always an issue. The radiation insulation to protect the astronauts also traps the heat in the station, and because convection doesn't exist in space they have to use heat exchangers that excel at radiation to remove all the waste heat.

One of the absolutely biggest design problems on the space station is keeping the whole damn thing sealed up while it's fluctuating +/- 250 F.

Hell, we struggle to calibrate our instruments using a 200mm ceramic bar. Just holding the bar too long while align it will throw it out on the under of 5-10 microns, even with coolant running.

The heating issue is not caused by "radiation shielding" which the ISS basically doesn't have. It's mostly caused by waste heat from the electronics coupled with solar heating.

 

[Dari]

Your forgetting that there is no air in space, that's why things that look"flimsy" do just fine, 20K MPH, 40K MPH is irrelevant, there is no wind resistance because there is no air..

I see. Then, what exactly is a solar wind?

 

[Dari]

If you're going to be retarded, at least don't post it out in the open for everyone to see.

The international space station sees extremes in temperature from 250 degrees F to -250 degrees F. That's just between the two sides of the space station, while in sight of the sun.

In fact, heat is always an issue. The radiation insulation to protect the astronauts also traps the heat in the station, and because convection doesn't exist in space they have to use heat exchangers that excel at radiation to remove all the waste heat.

One of the absolutely biggest design problems on the space station is keeping the whole damn thing sealed up while it's fluctuating +/- 250 F.

Hell, we struggle to calibrate our instruments using a 200mm ceramic bar. Just holding the bar too long while align it will throw it out on the under of 5-10 microns, even with coolant running.

Could you (or somebody else) rephrase this in layman's terms?

 

[diesbudt]

Do a quick google search for the contingency checklists and procedures that shuttles used to use. Aside from engine failures and a loss of cabin pressure the partial or complete failure of the cooling system was probably the most serious problem that they trained for. Temperature is a HUGE issue.

Yes I see that. My mistake, I was thinking of combustion engines when I said that, which is a whole wrong topic.

(This isnt my field of expertise)

Also Solar wind isnt' "wind" it is: The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time. These particles can escape the Sun's gravity because of their high kinetic energy and the high temperature of the corona.

http://en.wikipedia.org/wiki/Solar_wind