Real Science Time! For those of you not interested, you can go back to watching “America’s Funniest Groin Injuries” or reading the latest copies of FHM and BCN (“Barely Concealed Nipples”). This might be interesting as some background info for anyone interested in writing realistic space stories, however.
Let’s discuss the difficulties of sending a manned mission to the surface of Venus and getting them back again. We’ll ignore the difficulties of getting a crew from earth to Venusian orbit. Those are considerable, harder than getting to the moon, far easier than getting to Mars. What we’re going to concern ourselves with is actually *landing* and taking off again.
Venus has an atmosphere which is about as dense as our ocean ½ mile below the surface, the temperature is above the melting point of lead, and the atmosphere is highly corrosive and largely composed of hydrochloric acid vapor. As such, it presents a lot of problems, it’s not a garden spot, but it’s nothing a bunch of clever plastic-working monkeys like us can’t figure out.
First of all, there’s really no reason you’d use rockets to land on the surface of Venus. Once you kick yourself out of the atmosphere, it would make more sense just to use ballast tanks or a balloon or something. The atmosphere is so dense that it would eat up most of the re-entry velocity without needing to use any fuel, and then, since it’s so dense, getting about on the surface would be a snap - the whole lander could ‘float’ in the air like a minisub, and it could move around just by using small propellers. That’s right: Propellers! On a spaceship! How cool is that?
The failing here is that most modern authors (Not that there have been that many) who’ve dealt with these realities have either declared them unsolvable (Silly!), or have cheated and treated it like a lunar or Martian landing. In fact the environment is completely different, so those approaches aren’t appropriate, or even really feasible. I’m not ragging on them for it - they’re writers and producers after all, not scientists - I’m just pointing it out.
You find a site you think looks neat, your space-sub swims over, touches down, and your astronauts come out wearing something like a JIM suit. ( http://en.wikipedia.org/wiki/JIM_suit ) Limited surface time would be a problem, owing to the extreme conditions, but work sparingly, do as much with little grabby hands on the outside of the ship, like they do with Deep Sumbergance Vehicles, it’s not insurmountable, even if it is much harder than anything we’ve done before. As to the effects of the acidic atmosphere on the hull - again, problematic, but not inherently fatally so. I mean, they’ve got heat shields to get them through entry, these would theoretically work on the surface too, and if not, hell, just make the outer hull out of ceramic, which handles high temperatures well and is impervious to most acids.
What do we do about radiating the ship’s own operating heat? We clearly can’t dump it outside, refrigeration wont’ work without a heat dump of some part? I’ll admit I don’t have that worked out yet, though Nwkeys said that Ben Bova used an ablative coating of lead on the outside of a lander in one book. It gradually melted away like ice, taking heat away from the hull. That might work, but it seems awfully fragile. I admit I don’t have an answer for this one, but I’m sure it’s not insurmountable either, it’s just something that requires someone smarter than I am to come along and outclever me. It can happen.
Which brings us to the problems of liftoff, and this actually *is* pretty significant.
Problem Number One is the size of the launch vehicle you’d need, which is much, much bigger than you’d need to get off the surface of the Moon or Mars. All things being equal, Venus has gravity that’s insignificantly lower than earth. Let’s assume, for sake of argument, that the crew compartment of the lander is about the size and weight of an Apollo capsule. Now since the gravity on Venus is almost the same as on earth, it follows that it would take about as much energy to put a six-ton payload in orbit around Venus as it would on earth. It follows, then, that the lander would have to be about the same size as a Saturn 1B rocket - about 224 feet tall an about 22 feet wide. The fact that your lander can move about like a submarine might ameliorate some of this, but not much.
Problem Number Two is the high temperature on Venus: In order to work in an atmosphere, the combustion temperature of a rocket must be higher than the ambient temperature outside. If it isn’t, then you don’t really have a rocket, you’ve got an incredibly inefficient refrigerator (As Fred Phol pointed out), and it just won’t work. So you need some super-high energy fuel if you’re going to do it that way.
Problem Number Three is that in the extremely high pressure, it would be like attempting to launch a rocket from half a mile down in the ocean, which means that (A) you’ve got to build a rocket that can stand the higher pressures - which means a bigger, heavier, sturdier rocket than you’d use on earth - and (B) vastly more atmospheric resistance, which means you’d need to use more fuel.
All of these factors conspire to mean you’d need a rocket that’s much larger than a Saturn 1B, though probably not as big as a Saturn V, to get back off the surface, if you’re going to use a rocket to do it. And keep in mind that you need to actually somehow LAND this big beastie on Venus all in one piece in the first place. So: bottom line, it’s not an insurmountable problem, but it’s a toughie.
My solution? Use a small Nuclear Pulse Rocket. Have a big steel pusher plate on the bottom of your lander, and when you’re ready to go, drop a nuke - maybe half a kiloton, then another, then another, then another, and - bang! (Quite literally) - you’re in orbit!