It could be argued that the "Venus" forum on UMSF is for discussion of UNMANNED missions and this thread on a fantastical manned mission is out of place. The appearance of a manned flight thread in an unmanned flight forum invites comment on manned missions in general.

There is a specific forum for discussion of manned missions, real or imagined.

edit: I'm not against any mention of manned flight in any of the forums, I think it has its place. It's useful to use a theoretical human mission to discuss the environment of a planet, moon, etc. But I don't think the philosophy or nuts-and-bolts of a manned mission should be discussed outside of the manned flight forum.

"Sending Men To Venus" has had some interesting ideas. Should a manned orbiter control a rover? That's sort of a manned and an unmanned mission. The argument was made that if ISS is successful, then manned orbit of Mars or Venus would be successful. But that begs the question of the usefullness of ISS.

To me, unmanned spaceflight serves a short term goal of answering scientific questions. But I think it can have a long-term goal of preparing the way for manned exploration or colonization.

There is an important issue of how to plan that efficiently, but unfortunately, the space programs of every nation have been highly political. America sent men to the Moon because it had become a contest between the USA and USSR to prove who had the superior society. For China its propoganda, maintaining control of a dictatorship. For Europe, its a source of pride and emerging national identity as a union.

But given $100 billion, how do you make the most progress? Do you blow it on collecting one rock from Mars, and then never go back again? Do you build an expensive new space station to explore low-Earth orbit, so thoroughly understood already? Or do you dole it out to a series of robotic missions that lead up to some actual plan?

I don't see that plan. ISS and Bush's Mars and Moon missions all seem like missions with a politcial agenda. And scientists struggle and compete over the remaining slice of the NASA pie. Does everyone else believe things are just fine as they are?

This becomes a controversy only when people lose their tempers instead of engaging in discussion.

Incidently, I assume this thread can be moved to the "manned flight" folder at any time. Why not do so?

I would rather change the forum name from UMSF to SF. The guygs who are participating this forum aren't only bond to unmanned space flights but also of manned ones. Both are complementary. The manned space flights depends from unmanned space flights since the unmanned ones are the first to conquer the unknown frontiers. Then, the unmanned space flight will depend from manned space for a more advanced explorations that might happen in the future such as children spaceships obeying the commands from the mother spaceships to facilite special explorations.

Rodolfo

Not with the current budget. Sure, it would be great to plan a manned orbiting mission to Mars and talk about all the wonderful robots that they could control on the surface from orbit. But this is pure science fiction for the forseeable future.

Unfortunately the reality is that manned and unmanned missions are competing, fiercely, for sparce budget dollars.

Not going to happen. Ever. Want a place to talk about manned spaceflight in a major way, make one yourself. The manned spaceflight section here has been THIS CLOSE (fingers close together) to getting culled, because it's the place where 90% of the arguments, flame wars and resultant bans and mod activity have to happen.

There are plenty of places that disucss manned spaceflight...but very few that do what this place does.

Doug

Well, since Doug owns this forum, that's his call to make, though I'm sure he appreciates the input.

But for those who feel that their particular opinions are getting short shrift here, there's a simple, free solution to cure that. Once you get up and running, let me know. I'd love to read what you (and others) have to write on a given subject -- elsewhere.

Doug receives much deserved praise for maintaining a place for intelligent discussion of UMSF. He rightly (IMHO) sees that this quality would be jepardized if the forums were opened to discussion of manned flight. I generally trust current UMSF members, but once the Buck Rogers, spaceplane types showed up I would face the same problem picking through the forums for realistic, rational discussion of UMSF as I do on other web sites.

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Don, I must say that, with your clarifications, I agree with you much more than I don't.

This thread is good, I think -- though there is a definite self-limiting factor to a manned Venus orbiter right now (energetic cosmic rays and solar flares, with no really good way to shield against them). To safely operate manned vehicles at Venus, I think you'd first need to maneuver an asteroid into orbit around it and dig your manned vehicle into that asteroid. (Unlike Mars, Venus doesn't present us with a ready-made natural piece of real estate in the right location.)

I somehow get a feeling that, by the time we know enough to be able to maneuver asteroids into planetary orbits, we'll have come up with a shielding solution for energetic particles...

-the other Doug

It's not THAT difficult to shield solar cosmic rays. They're relatively low energy. You do need pounds of mass <perferably low atomic weight mass> per square inch surrounding you (sea level on earth has 14 pounds of mass per square inch over it)

What's a real problem is high atomic weight high energy galactic cosmic rays. But 14 lb/sq-in stops most of them, and shatters most into smaller and lower energy particles (cosmic-ray showers, they call'm)

The problem is the simple one of having to live inside a radiation shelter most of the mission. And you have to take that mass with you whereever you go.

I worked on the heavy-nuclei detector in HEAO-C. We actually calibrated it in space using iron nuclei, which are pretty abundant in cosmic rays. I've heard that astronauts occasionally see flashes of light, when one of these passes through their eye and generate Cherenkov radiation.

There has been some research on using strong magnetic fields to shield a craft from cosmic rays. I don't know if that is practical or not.

Perhaps research on suspended animation will open up better possibilities for dealing with multi-year interplanetary missions -- allowing a crew to be kept safe in small shielded areas, and eliminating the need for massive supplies. Some dogs have been maintained in a clinically dead state for many hours without ill effect. But it's far from perfected or safe at this point.

Don:

I think the mechanism for 'seeing' cosmic rays actually involves direct stimulation of the optic nerve - the eyes aren't involved at all.

It's still scary!

Bob Shaw

[...]

Were there ever a set of results posted for the ALFMED experiments flown during Apollo lunar missions? They had a nice setup, with a head-enclosing box that contained film on five of six sides. The idea was that you'd be able to calibrate film hits against taped reports of light flashes reported by the test subjects.

One of the things this was supposed to settle was whether the crews were seeing real light generated inside their eyeballs, or whether the flashes were indeed the result of direct hits on the optic nerves of the brain.

I don't ever recall seeing any results that settled this question. Anyone have any more info about it?

-the other Doug

Why send such things, when you can use piles of rock and ice that Nature has provided? Assuming you can find piles of ice and rock in the orbits you want to use, of course.

Really, though -- just dig into a low-mass moon or asteroid, and you're all set. This would work for most of the worlds in our system, with the exceptions of Mercury and Venus...

-the other Doug

Provided you can put a few tens of thousands of tons of hardware into orbit even that isn't an issue. Find a small near-Earth asteroid, land a mass-driver and some kind of decent power plant -- be it nuclear or solar -- on the asteroid and your 'home' also becomes your fuel supply. It won't get anywhere fast, but by throwing the rock out the back of the mass-driver you can take it to orbit pretty much any planet in the solar system.

Personally though I doubt people will ever land on another planet until they're doing it as a tourist trip. Venus is really kind of a no-hoper due to the atmosphere and surface conditions, where unmanned probes are clearly superior to humans (though obviously rovers controlled from orbit could move faster than rovers controlled from Earth), and while the Apollo astronauts probably achieved more in a few days in localised areas on the Moon than an unmanned probe would in months, for the cost of a manned trip to Mars with today's technology that could thorougly study one area you could 'pattern-bomb' Mars with a thousand or more unmanned rovers and get a good overview of the entire planet... I can't help but feel that the latter would be much better value for money.

I think both effects exist. During the Apollo missions, flashes of light were seen, and these were explained as Cherenkov radiation in the vitreous humour. X-rays and gamma rays can also stimulate the optic nerve and brain.

Super energetic cosmic rays can cause the whole sky to flash. I don't believe the human eye can see this, but there are detectors that essentially use the night sky as a giant detector for these rare events.

OK, here's a question that reveals an area of ignorance on my part...

We have a pretty decent idea of the energetic cosmic radiation levels outside of Earth's protective Van Allen belts. We also know we can see a certain number of these particles on Earth's surface itself (ever seen one of those nifty cloud scintillation chambers that were all the rage 40 years ago?), so we know that not all of these particles are shielded at the Earth's surface. (At least, when I saw one in grade school, they told me that the trails were energetic cosmic rays.)

The question is, what is the relative level of shielding provided by the Earth's magnetic field? I'm just looking for an order-of-magnitude feel for the thing -- is 1/10,000th of the unshielded flux coming through, or more, or less? That kind of thing.

-the other Doug

Here is some information from Caltech's Space Radation Lab (where I was a grad student ages ago).

Interplanetary Dose

History

Radiation is also highly concentrated within the Earth's radation belt, so the most dangerous place to be is a few hundred miles above where ISS is orbiting. In the outer belt, you would get a lethal dose or radation in a couple days.

The Earth's magnetic field looks like it may collapse for a while and possibly reverse, sometime in the next thousand years or so. The field is already about half the strength that it was during the Roman era. The Earth's atmosphere is plenty of shielding against space radiation, but I've already heard people make bizarre and dire claims about what will happen then.

[...]

It still occurs to me that surface sample return is beyond our capabilities at the moment. Venus has a gravity field very similar to that of Earth -- you would need something more powerful than a Delta II to get a sample off the surface and into an escape trajectory, I would think (especially when you consider how much more atmospheric drag it would encounter on the way up).

That's an awfully big rocket to land on Venus and to engineer such that it will survive any sort of surface stay long enough for teleoperations.

Here's a question, though: just how valuable would a sample of Venusian air, collected at, say, 50km altitude, be? We're still above a lot of the atmosphere at 50km, right? You could design an entry probe to pump a chamber full of Venusian air (complete with dust particles, etc.), or perhaps several chambers at different altitudes. Then, when the vehicle is still moving relatively fast (we're talking Mach 6 to Mach 10 operations, here) all you would really need to boost the sample chamber(s) back to an escape trajectory would be something like one of those air-to-orbit rockets.

I'd think the data on isotope abundances and elemental compositions of dust particles would make the samples worthwhile, and you could collect such samples and then rendezvous the collection chamber(s) with a manned flyby, just as John described.

What do y'all think?

-the other Doug

[...]

With the density of Venus' atmosphere, I think any rocket would have severe gravity loss penalties. You would need to avoid any significant dynamic pressure (easily builds up in Venus atmospheric density) and I think that'd actually imply subsonic velocities (and you still might have high losses due to air drag) for much of the atmospheric ride up.

How does this translate to gravity losses? If you're constrained to a velocity, your acceleration is even more constrained. The best (cheapest in terms of delta-V) way to get something into orbit is to send it up as fast as possible to minimize the time gravity decelerates you before you go on a ballistic trajectory with negligible further gravity losses. Fast accelerating rockets in other words. On Venus, your inertial acceleration would be limited to about 1 G (giving a total of about zero for early phases of flight) for a long time so the gravity losses would skyrocket. You'd need much more total delta-V imparted by the rocket than on Earth precisely because you're not allowed to accelerate fast enough in the lower atmosphere.

It begs the question if rockets can be even remotely feasible on Venus and that's even neglecting high surface temperatures and pressures and issues they cause with propellants.

I don't know if this has already been considered but I think its worth mentioning.

Recently I had been examining atmospheric profiles of Venus and have noticed that if one were considering sending humans to the planet, it may be better to build some kind of floatable module that can hover at a certain height in the Venusian atmosphere with Terran air pressure and temperature. I can't recall how high exactly (17km?) but what I do know is that it is 'safe enough haven' for manned exploration.

[...]

I like the floating base idea. Balloons, not rockets, would probably be the best way down to the surface and back up to it.

To get from the base into space, perhaps the best bet would be a rocket with some sort of lifting body so it could accelerate horizontally rather than straight up. At least you're never thrusting directly against gravity then. (And you don't need to design a rocket that'll work at 600 C). It'd need to bring its own H2 for the return flight, but the O2 could be made in situ, and that's 75% of the mass requirement.

--Greg