The Great Unknowns of Space Radiation

If one lies out on a Florida beach in mid summer, what is the difference between 12.6 minutes and 17 hours? Anyone who has ever had the misfortune of 17 hours bare skinned under the Florida sunshine will tell you that it’s probably time for a long visit to the hospital. How about the visit that lasted 12.6 minutes? For most people, it would not even change the color of the skin.

Why is any of that important? Because that is the same time comparison between the Apollo 17 mission and a minimal trip to Mars. And what does a Florida beach have to do with that? It illustrates an interesting difference in radiation exposure. Even though the radiation species is not the same, the long term exposure effect differences are!

While we have the glorious background of men going to the moon, comparing the Apollo moon flights to a Mars expedition is not the same discussion at all. That fact seems to have been lost on many expectations.

For the entire mission, the astronauts will be exposing their mid-brains to the heavy particles of spaceborne radiation traveling at near light speed with energies measured in billions of electron volts. Again, making the comparison of earthly medical or even nuclear power source radiation is wholly inappropriate. A single LET track of space radiation will leave a track through the cell(s) it kills easily observable with visible-light microscopy.

What is my point? We need to stop comparing Apollo experience with what is coming and we need to get busy designing systems for the long missions and not relying on camping trip technology.

Check out my longer discussion on this at:

http://quantumeditions.com/quantumlimit

I've checked out your website, and found it contained a lot of scientific errors, but your essential point about the duration of radiation exposure is correct. Increased shielding, however, would reduce the exposure.

It would not be very difficult to mitigate the prolonged exposure of a Mars mission. Apollo astronauts had very little shielding, especially in the Lunar Module. A reasonably well equipped Mars mission would have to carry substantial amounts of propellant and water, which with proper design, could be used very effectively to shield the crew quarters.

It all comes down to mass. Trying to fly a Mars mission starting with one or two hundred mT in LEO will lead to low safety margins and high risk. Do it starting with 1000 mT in LEO and it all becomes much easier and safer.

If you're going to wait for the ability to get 1000mT into orbit and low risk then the event will never happen. That's why NASA will never get to Mars. They've even removed it from the VSE and are now only focusing on the Moon.

If we look at some real life examples of risk taking eg. Everest expeditions where the mortality rate is about 10%, then those are the risk levels we should apply to a Mars expedition, not the unrealistic levels NASA is striving and failing to reach. If you get support for a risky venture in terms of money and the capability then it will happen. There will always be those willing to risk life and limb to be first. Actually we pretty much have the capability, only funding and some serious risk takers remain to be found.

Check out RPSpeck's website:

http://www.micro-space.com/

What about a Mars-roundtrip carrying insects or smallest mammals? Then a small vehicles could be used - a reusable one perhaps.

At return the animals could be checked for the effects of radiation.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

That is an AWESOME idea! As a matter of fact, the same sort of experiment could be conducted by a long, eliptical earth-moon orbit by a life sciences spacecraft carrying rodents. This would expose them to the same radiaiton they would receive on the Way to Mars and they would be readily accessible.

That's precisely why the US lost the race to be the first to put a man in space. Even then, they were extremely cautious. I'm not against reducing risk but putting an animal up first doesn't in the slightest way address that issue. Besides, I'm against the idea of putting an form of life in space in place of a man/woman for practical reasons. If something goes wrong there's no chance of recovery whereas a man/woman can react and possibly retrieve the situation. Besides, there'd be no shortage of takers.

Now there's an idea that is a rare one indeed! Protect the animals and let the stupid humans go. But when the stupid humans are lining up fifty deep to be the lab animals, it's actually difficult to argue the point! Your point on instutionalized aversion to risk is well taken, however, and there is more than just a grain of truth to it. I do believe that this whole issue will go away when we can get the private enterprises up and running. If we can keep the FAA out of the risk aversion business, then the human volunteers will be allowed to choose their own fates for their own reasons - whatever it turns out to be.

Now having said that, I have no issue with rats in space. Since they are considered dangerous vermin over the entire world and exterminated without any prejudice, it is hard to mount an argument on using them as human proxies when done humanely and with the proper controls in place.

I really like the idea of testing mice or insects or even microbes for long duration radiation exposure outside the Earth's magnetic field. It could be done cheaply and soon and there is no reason not to do it. I would go further and say that after that data is in and shows we can safely do it, we need a shakedown flight of the actual Mars vehicle, orbiting outside Earth’s magnetic field, maybe at an Earth-Moon Lagrange point or very high Earth orbit above GEO. A crew would occupy the vehicle and test the reliability of the systems without being stuck far away from rescue in the event of some kind of failure. Even the people who sail around the world solo first have shake down cruises in local waters. It is just common sense.

I realise I'm in the minority with respect for the life of all creatures however mankind has the ability to choose whereas insects, mice, and other 'animals' don't hence my argument that it is unethical to use them in that way. I'm being consistent with personal beliefs here as I'm vegetarian. Naturally some will argue about eating vegies but so far no one (to my knowledge) has managed to demonstrate emotions in a cabbage but when they do, I'll have to revise my belief system and just live on water and air.
Look, with respect to radiation experiments, there's plenty of instrumentation that can tell us what we'll face out there in space. Even the MER's were partially protected by spinning their vehicles although that was done mainly to keep them on course.
But I agree with the general thrust of this argument, get the packages out there and then also the shake-down flight - just do it. Why all the procrastination?

By the way, here is a great NASA report on Apollo radiation exposure and effects.
http://lsda.jsc.nasa.gov/books/apollo/S2ch3.htm

What's the point of a shake-down cruise around the moon? The vehicle will be discarded afterwards, and a brand new, untested one used for the Mars mission. Nowhere in ESAS does NASA intend to re-use any craft except the CEV, and that only after extensive refurbishment, on the ground!

NASA can't or won't reuse a manned space vehicle without such extensive, intensive & expensive maintenance, [ISS excepted, but since it doesn't really go anywhere, is it a vehicle? ]. They don't seem willing to fire any large rocket engine more than once or twice. And given the way they build their spacecraft, I totally agree. In order to fit everything needed for a Moon landing on one CaLV, everything must be lightweight, leading to high cost, low margins & limited performance.

An alternate approach is to design a vehicle for each phase of the mission, make them safe, effective, robust & re-usable. Then independently launch them and fuel/refuel in space. e.g.

A small launch/re-entry capsule for human access to LEO. Launched on a smaller version of the CLV or Stick.

A large inter-orbital crew ferry, with plenty of radiation protection, and micro-gravity mitigation devices. For transport between LEO and Moon, Mars or other orbit.

A large crew/cargo lander, with sufficient deltaV to land a substantial payload anywhere on the moon, then launch back to lunar orbit, without refueling or dropping a descent stage. Dropping empty fuel tanks for later re-use may be acceptable. Refueling would probably be required for launch from Mars.

A large, but slow, unmanned, inter-orbital cargo ferry, for transport of fuel and other cargo between LEO and Moon, Mars or other orbit.

Automated resupply stations in LEO, Moon & Mars orbit, using standardized cargo pods and fuel, oxidizer, air & water tanks.

Each of these (except the capsule) would require its own CaLV launch, but then would be used for many years and support tens or hundreds of missions.

A third class of launchers would be required for low value, bulk cargo, like fuel & water. Tenders could be offered for delivery of standard pods & tanks to the LEO depot, stimulating the development of new low cost launchers. And/or a very large low cost launcher like Sea Dragon could be developed.

It's time we start building spacecraft like ships, instead of expendable munitions.

To prove the systems design and verify the crew is not harmed by radiation (or or anything else) during a 2 year exposure.
That is what the Shuttle was supposed to be. It seems we are not up to the task yet.

Supposed to be, maybe. More like an airplane in initial concept. But it was designed and built by missile makers. So we ended up with a winged missile that can be refurbished & reused at great expense.

I wonder what the unit cost of a non-reusable shuttle would have been, assuming 250+ were built over 25 years? It wouldn't surprise me if was a lot less than the current cost per flight.

Nobody is trying to build a spaceSHIP, because weight is seen as the key design factor. Low weight means low margins, low reliability, high complexity & high cost. Not condusive to re-useability

Hello, WannabeSpaceCadet,

please keep in ind your hint that a untested new vehicle would be used for the Mars mission and also that expendable rockets and vehicles are so expensive because of the high hardware costs.

Because of this it allways will be cheaper to use reusable vehicles - but to look for the best radiation protection there shoud be particular reusable vehicle for test of equipments. Such vehicles should allow for quick and easy replacement of equipment - which I suppose to mean that they can't be used for real missions.

By such a vehicle alternative shields etc. could be experimentes with and tested.

Regarding the insects and small mammals to investigate the impacts of remaining radiation on beings - what about replacing them at the first flights by cultures of cells which aren't beings yet but would evolve into ones over a period of time?

What about that?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

It seems that NASA is heading into space with flies.

http://www.spaceref.com/news/viewpr.html?pid=20144