No scripts / Mars roundtable 11.28


#1

What a great episode!
Just wanted to say that :wink:


#2

agreed. great topic and very compelling dialog. Thanks TMRO!


#3

It was great to see all the energy in the show and after dark. Well done all.


#4

Open-ended discussions are great … Start with Why Mars … then GO! I really enjoyed the Mars roundtable and the After Dark that followed.


#5

I was disappointed that I couldn’t watch this one live! Great discussion!

I’d like to comment on two things that were brought up in the roundtable: radiation and artificial gravity.

On the radiation side of things, I’ve got three points. The first is simple: with current career radiation dose limits for NASA, it’s not possible to do a manned Mars mission with current technology, even if the entire crew were complete rookies. Even with advanced propulsion systems, the crew are in space too long to avoid this, even if they received zero dose on the surface. ESA, JAXA, and Roscosmos all have higher career rad limits than NASA does, and even then it’s difficult.

The vast majority of the ionizing radiation is charged particles. NASA has been working with a number of organizations, but most notably the Rutherford Appleton Laboratory in the UK, to develop artificial magnetospheres for spacecraft that don’t cause the payload (and crew) to deal with a high magnetic flux. This means that while they’re in space, the crew would be able to receive a far smaller dose.

As a side note, the faster you get to Mars, the less radiation you receive. Once there, it’s likely that the habitat will be buried, so it’s less of a concern, the trip there and back is the problem.This is why NASA has planned on the use of NTP (nuclear thermal propulsion) or BNTP (bimodal nuclear thermal propulsion, basically NTP that also produces electricity for a big ion drive) since the 1970s, and those plans haven’t changed. NTP cuts off weeks of trip time, and BNTP months. This is why NASA’s putting so much money into NTP, and why the planned crewed mission schedule is driven by engine development.

For the microgravity concerns, the SpaceX design is the only serious plan to get to Mars that DOESN’T use centrifugal gravity in one form or another, and again this goes back to the 1970s. Most spacecraft that are carrying enough propellant, supplies, etc for the trip are long and thin (look up the Boeing IMIS proposal for the original planned spacecraft), which means flipping end over end is a perfectly easy way to get comfortable artificial gravity (the term is “tumbling pigeon”). Other designs have two habs on either end of the main axis of your spacecraft (like the Hermes from the Martian, which is based on a Stan Borowski NASA design), but this adds weight and complexity.

Without gravity, your crew won’t be able to do anything on Mars due to microgravity problems, and will be completely disabled on their return to Earth, if not dead due to medical complications of microgravity. NASA hasn’t seen a way around this in decades of study.


#6

The gravity situation isn’t quite that bad. Most of the worst effects of a 3 to 5 month period without gravity can be compensated for with the Advanced Resistive Exercise Device (ARED). The most debilitating will be the disturbances to the cerebellum, which cause a short period after landing where people find it hard to keep their balance. This period is only about 3 days though, so people can take the time they need adjusting their brains back to having gravity by controlling robots which can do the heavy lifting of unloading, initial ground clearance, and site construction.

That being said, I also support artificial gravity 100%, it’s a must have technology for trips longer than Mars transit.


Loehr J.A., et al. Musculoskeletal Adaptations to Training with the Advanced Resistive Exercise Device. Med. Sci. Sports Exerc., Vol. 43, No. 1, pp. 146–156. 2011.