7
$\begingroup$

Among other reasons, the high pressure of Venus and the gas giants atmospheres are often stated as one of the major problems for an unmanned lander. They say the pressure will "crush" the probe. Why is high pressure a problem? Of course you can not have a confined space of gas or vacuum , or foam containing small bubbles of air on-board, but that should be easy to avoid.

edit: Just to clarify, I am totally aware of the terrible environment of Venus, I just wonder about why high pressure in general is a problem.

$\endgroup$
  • $\begingroup$ Engines won't work with huge atmospheric backpressure. $\endgroup$ – Deer Hunter Dec 29 '15 at 17:19
  • 2
    $\begingroup$ @DeerHunter But for landing parachutes work even better... $\endgroup$ – Hohmannfan Dec 29 '15 at 17:24
  • $\begingroup$ The problem for Venus is its high pressure combined with its corrosive atmosphere, IIRC. You can't let the outside air in because it'll attack everything inside. $\endgroup$ – Hobbes Dec 29 '15 at 19:14
  • 1
    $\begingroup$ If pressure by itself wasn't a problem, the sea bed on Earth would have been extensively explored long ago. The affect of pressure is the same irrespective of whether it's from a wet liquid or a dry gas. The other issue with pressure is that craft made to tolerate pressure end up being heavy due to wall thicknesses. This becomes an issue for rockets and launching such craft. $\endgroup$ – Fred Dec 30 '15 at 1:31
6
$\begingroup$

The pressure at the surface of Venus is about 92 atmospheres -- 1400 lbs per square inch, almost 100kg per square centimeter (9.2 MPa).

Many solid, homogenous materials can withstand that, but consider something like an integrated circuit chip, where different metals are layered within a plastic or ceramic carrier. If the different material layers flex by slightly different amounts under the pressure, something is going to crack.

More of a problem than the pressure itself, though, is heat. The surface temperature on Venus is about 460ºC. A lander won't be able to keep its instruments and other electronics cool enough to function for very long.

$\endgroup$
  • $\begingroup$ The pressure would cause things to crack, really? If I have a brittle metal structure at the bottom of the Mariana trench, it is not going to crack, unless it has confined internal spaces. That is over a 1000 atmospheres of pressure. $\endgroup$ – Hohmannfan Dec 29 '15 at 18:14
  • 4
    $\begingroup$ Imagine you have two bars of different materials bonded together along their length. Imagine that under high pressure, one shrinks by 1% and the other shrinks by 0.5%. One of two things must happen: the assembly will bend, or the two parts must come unbonded. $\endgroup$ – Russell Borogove Dec 29 '15 at 18:38
  • 1
    $\begingroup$ You might want add something about the a material parameter like the Poisson ratio which can tell how much a given material will contract for a given stress, in this case homogeneous pressure. Materials like rubber hardly contract, however most metals and other materials do, and do so by different amounts. This can induce internal stresses at the interfaces between those materials, and thus might fail. $\endgroup$ – fibonatic Dec 30 '15 at 5:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.