Von Braun's Manned Mars Expedition (II)

I was surfing YouTube, and came apon an interesting clip: sometime in the 1950’s Von Braun proposed amanned expedition to Mars, using spacecraft that looked like giant pinwheels. Unlike his massive fleet of chemical propellant rockets, these ships were powered by electric propulsion (ionized caesium atome, accelerated by ahigh voltage electric fiels. The ships were powered by nuclear reactors, in which the reactors heated a silicon oil working fluide which drove turbines/generators.
Because the mass of the propollant gas was so low, the craft (a fleet of five ships) would have to make several spiralling orbits of the earth, to attain escape velocity.
Was this ionic prpulsion ever tested? And, would nuclear reactors in space work? Seems like shedding the exhaust heat might be a problem.

Wikipedia has a decent article on ion propulsion. Practical engines have been developed and have been used on satellites, mostly for stabilization control.

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

Nuclear reactors can be made to work in space, though as you noted there are some engineering challenges to making it practical. The Soviets lead in this field. Wikipedia has a decent article on their Topaz and Topaz II reactors.

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

The U.S. has also put a reactor into space.

Shedding heat is why the ships looked like pinwheels; the “flower petals” are radiators.

Disney’s “Man in Space” TV series had a chapter on these ships.

That is fascinating… using 80’s tech, creating a generator that wasn’t that large, that could provide 5kw steady for 3-5 years. Makes me wonder why it hasn’t been developed more for deep space exploration?

Oh wait… nuclear. Nevermind. :frowning:

Those of us who grew up in the '50s read lots of books with these missions laid out, usually by von Braun or Willy Ley. Lots of color pictures of the mission, and yes, the Disney series was based on them. Alas, the ones I read are from the library and I don’t have any in my collection.

Back then it was commonly assumed that you would need a space station before even heading for the moon, let alone Mars.

That’s an interesting suggestion. For manned missions, how beneficial would it be to have a large station in orbit where (I assume) you could assemble and refuel (and do other stuff I haven’t thought of to) ships before they got on their inter-planetary trek? Enough to make building the station worth while?

It would seem to me that you’ve got to get that mass up there one way or another. I suppose if the Saturn V weren’t available you could take it all up to orbit piece by piece with several launches, but I don’t see why you would need a space station for that.

Probably because nuclear reactors are heavy, complex, and more powerful than you need for a deep-space probe. RTGs are much simpler (no moving parts) and better suited for space probes. They are still used.

Having a space station in orbit isn’t imperative or even necessarily useful for a one-off mission; you could even send up a core habitat module that acts as a space station until you add on command, propulsion, and mission modules to it to make your interplanetary spacecraft. However, if your plan is to build a space infrastructure to support mining, refining, or manufacturing of propellants or structural materials in space to support ongoing exploration and permanent habitation, one or more permanent space stations are imperative.

However, RTGs have a very low specific output; enough to minimally power a ballistic space probe for a few decades, but not enough to provide energy for propulsion or keep people alive for a few years. For that, a nuclear reactor or some other compact, high specific output power source is necessary. If you are exploring the in-system, solar is probably more practical in terms of complexity and weight, but in the out-system (beyond Mars) solar flux becomes a fraction of what it is at Earth’s orbit, and you would have to be able to supplement or replace it with some other power source, like a nuclear reactor.

Although the US has had some modest experience with the use of nuclear reactors in space and nuclear propulsion (NERVA), none of it has been at the mature production level, and research in this area has pretty much been dormant since 1972. The people who have familiarity with practical nuclear thermal rocket applications are either dead or retired. We would have to build up a new heritage of experience. This isn’t ion propulsion, of course; it is nuclear thermal, and therefore higher thrust but lower I[sub]sp[/sub] (specific impulse, or impulse imparted per mass of propellant expended). The thing about electrostatic ion propulsion, however, is while the I[sub]sp[/sub] is high, the overall energy efficiency is quite low, often 1-2%, and it doesn’t scale up well to larger applications. These are used exclusively for stationkeeping and low thrust space probe applications (Deep Space 1, Hayabusa, DAWN). Electromagnetic thrusters using magnetoplasmadynamic thrusters or VASMIR offer far more scalability but have very high power threshold requirements and fine control of magnetic fields that is currently at the bleeding edge of space propulsion technology.

The problem with getting a nuclear payload to space are twofold: one is that it has to be unitary; it isn’t practical to assemble a nuclear reactor in space, and so the size and mass of such a unit is limited to existing space launch vehicle capabilities. By going to a modular system this can be mitigated somewhat, but it still places some design constraints. The other, and a major factor that has prevented the US from developing nuclear propulsion technology, is the hazard posed by the failure of an SLV to make orbit. It will be very difficult to fully encapsulate a large reactor and ensure that it will survive an abort or range destruct intact, and salting the downrange with long lived radioactive isotopes and toxic heavy metals is a bad thing, publicity-wise, even if the statistical casualty calculations show only a minor increase in E[sub]c[/sub]. This is what killed ORION, and will heavily restrict any ground-to-orbit launch of active nuclear reactors unless an onerous and impractical level of payload survivability can be demonstrated. Nuclear space propulsion will probably have to await the ability to produce and assemble fuel elements in space.

Stranger

Von Braun was both a pragmatist and publicist. He knew a very great deal about conventional liquid fuel rockets. Other ideas such as a space station, nuclear power and ion drives – and here I’m not criticising – should be considered publicity.

Disney also turned the ideas of another prominent thinker into film with “Victory Through Air Power”, based on the ideas of Alexander P. Seversky. There’s opinion voiced that Disney’s 1943 movie had a particularly unfortunate effect on American air strategy in WWII – vastly overestimating the effectiveness of bombers. That’s because Seversky was voicing an untested opinion. However Disney and others saw “Victory Through Air Power” as a great accomplishment. Hence some of Disney’s interested in “the next big thing” in the 1950s.

Von Braun, however, was one of the two undisputed geniuses of rocketry, so even his guesswork about the distant future for publicity purposes was liable to have practical value.

Von Braun’s tenure at NASA ended due to politics at the point the moon missions were winding down, so he had little chance to put his longer term plans in effect. And that’s unfortunate, because we ended up with the Space Shuttle, which is the biggest, most expensive and scientifically unfortunate technical dog the world ever created, except perhaps in some respects the Concord supersonic plane.

Thanks…in some ways, the 1950’s USA was unique-it looked like there was nothing that US money and technology could not accomplish!
Just looking at those old Disney films (and the Chesley Bonestall space paintings) brings a tear to my eyes-imagine what we could have done if we had the will (and didn’t get into places like Vietnam).

There was quite a bit of salesmanship in those depictions, too. We thrashed this out in an earlier thread, where I wondered why it was that the old Colliers/chesley Bonestell/von Braun/Disney depictions of the 1950s looked so completely different from what was produced. They uniformly showed very rounded objects, with streamlined spaceships and balloon-like space stations. When we got to the 1960s actual spacecraft they had projections and non-rounded surfaces. Even in our fictional depictions, like 2001, the space station was no longer a nicely rounded inner tube, but a squared-off and projection-covered double wheel, which somehow seemed more realistic.
It’s been admitted since that von Braun’s rockets would have to be much larger than depicted in order to carry the payloads desired. His space station wouldn’t have produced one gee, but significantly lower than that. (So would the centrifuge on the spacecraft in 2001, although they didn’t show it that way).

I’ve thought the same thing. The United States had a window of opportunity that has now passed. The Space Shuttle was a horrible mistake. If we’d continued building Saturn V’s for an additional ten years, we’d certainly be on the moon now, and perhaps even Mars.

By the time I got to NASA, the Space Shuttle had been sucking vital blood from the program for years, and the attempt to revitalize it with the ISS was misguided. I remember no one really seemed to have a good idea what it should be for.

Now we have a bureaucratic, slow-moving organization that’s better suited to research and modest-size projects than anything revolutionary – the way the Saturn V and moon lander were.

Luckily, robotics have come of age, which are cheaper and easier for the NASA organization to handle.

There is an irony in the Chinese developing manned space flight at this moment. I was talking to an acquaintance who worked as a Chinese translator at the UN. He was quite taken back when I said that the Chinese were buying a pig-in-a-poke. Lol. I wonder what he reported back to China of that conversation.

Three things going on:

  1. Spheres are the shape best able to handle uniform external pressure, followed by cylinders. Spheres are the shape that has the highest volume for surface area. So the thinking was spheres would be the most economical, cylinders next most. (Note that the ISS is largely made of cylinders.)

  2. Non-rounded surfaces got a boost when it was discovered, testing early manned capsules, that the blunt surface created a shock wave which created less overall drag than turbulence all along a surface would. This wasn’t understood in the 1950s, because we didn’t have vehicles that moved fast enough to notice the effect.

  3. For all that we have advanced in manufacturing, flat rectangular surfaces are still the cheapest to design for and manufacture. Picture your basic specialist NASA team of today, designing a special purpose satellite, rover, telescope mechanism, whatever. Where’s the intellectual horsepower? In the cutting edge stuff that’s just becoming practical – whatever it is. Over the last decades more and more of spacecraft development is software. So … you get together a team of qualified engineers … including a high proportion of software engineers … and not one knows or cares much about metal fabrication. Sure, the Martian rovers would be very marginally better at maintaining heat with rounded surfaces, but if heat was really a problem, they’d tackle it by designing in more power – a design option that’s well understood.

A good illustration of the thinking at the time is the series of stories by Clarke called “Venture to the Moon” which were published in 1956-1957. These involve a lot of spaceships, assembled at a space station, and a long stay. This was a pretty common model of lunar exploration, certainly more common than two guys staying less than a day for the first trip. I don’t recall any stories from the time with lunar orbit rendezvous techniques.

Wasn’t there a proposal, in the 1960’s to make a shperical space station? The station would be like a gian balloon-it would be held togther by the internal air pressure.
Seemed like a cool idea to me!