Author Topic: Mars Direct updated for the 21st Century  (Read 7464 times)

Offline envy887

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Re: Mars Direct updated for the 21st Century
« Reply #40 on: 12/04/2017 07:38 PM »
I can't comment on the absurdity of a colony because its off topic. But I can say that 5 tonnes per colonist is hopelessly unrealistic.

What I will say that is on topic is that 6gs is a lot of force on a civilian plucked at random. What makes it worse is months of bone loss in zero g.

Its not a case of grinning and bearing. Its a case of being stretchered out.

Years ago when I was a lot younger and fitter I pulled 6.5 g in a jet fighter for about 20 seconds.  Not being a dedicated pilot, I was wrecked for a good 24 hours afterwards.  A barely trained person enduring those g's for 5+ minutes during EDL is going to suffer for days.

Mars entry and descent after a fast transit is only about 8,000 m/s of delta-v. That's 3 minutes at 5 g or 2.5 minutes at 6 g. 5 minutes at 6.5 g would be over 22,000 m/s of delta-v.

Ballistic entries on Soyuz go over 8 g and also scrub off about 7,500 m/s of delta-v without injuring crew returning from months of zero-z on ISS. The Soyuz 7K-ST No. 16L abort hit 15-17 g for a few seconds without harming the crew. And Soyuz crash-lands at the end of all that.

Online KelvinZero

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Re: Mars Direct updated for the 21st Century
« Reply #41 on: 12/04/2017 08:38 PM »
Kelvin that's still for healthy people who haven't lost bone density in zero g.
My understanding is that for colonists, the trip time has to be only 3 months in order to reuse the BFS each synod.

We have a lot of experience with that timeframe, including reentry afterwards. A lot of medical science has been done to model the effects, and predict the effects of exercise (or lack of)

It also isn't happening tomorrow. There will be experience with small crews to Mars. Probably there will be experience with moon bases. Maybe colonists will need some sort of regimen. Personally I think anyone choosing to go to mars should first spend a year in a simulated Mars base on earth. It is not something to do on a whim like buying an airline ticket. This could also help prevent disease outbreaks in flight, and help with developing mars base technology.

The big unknown at the moment seems to be long term bone health in moon and mars gravity. Maybe even a single synod in Mars gravity will be debilitating. As far as I know, that could still be a show stopper. Im not claiming to be an expert though. Perhaps science can already make a very good guess. We will know before it progresses to 100 colonist trips though.

Offline tdperk

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Re: Mars Direct updated for the 21st Century
« Reply #42 on: 12/05/2017 12:43 AM »
Kelvin that's still for healthy people who haven't lost bone density in zero g.
My understanding is that for colonists, the trip time has to be only 3 months in order to reuse the BFS each synod.

We have a lot of experience with that timeframe, including reentry afterwards. A lot of medical science has been done to model the effects, and predict the effects of exercise (or lack of)

It also isn't happening tomorrow. There will be experience with small crews to Mars. Probably there will be experience with moon bases. Maybe colonists will need some sort of regimen. Personally I think anyone choosing to go to mars should first spend a year in a simulated Mars base on earth. It is not something to do on a whim like buying an airline ticket. This could also help prevent disease outbreaks in flight, and help with developing mars base technology.

The big unknown at the moment seems to be long term bone health in moon and mars gravity. Maybe even a single synod in Mars gravity will be debilitating. As far as I know, that could still be a show stopper. Im not claiming to be an expert though. Perhaps science can already make a very good guess. We will know before it progresses to 100 colonist trips though.

I believe we already know a full year in uG on the ISS is not a showstopper.  I have no reason to think the 1/3rd G of Mars would be.  Potentially worthwhile sending up a well chained chimp and returning them first.

Or a volunteer.

Online KelvinZero

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Re: Mars Direct updated for the 21st Century
« Reply #43 on: 12/05/2017 05:00 AM »
I believe we already know a full year in uG on the ISS is not a showstopper.  I have no reason to think the 1/3rd G of Mars would be.  Potentially worthwhile sending up a well chained chimp and returning them first.

Or a volunteer.
I think there is time to work it out too. Supposing Mars does turn out to be a failure, eaten by space goat or something, we could just choose another direction like asteroid colonies and space habitats with full 1g spin gravity. I personally expect significant LEO space tourism before mars, if Elon really achieves the "747 of space" that the plan hinges on. BFS carrying 100 colonists probably doesn't happen until at least 3 or 4 synods and a lot of experience in cislunar space could happen before that, if this thing is flying regularly.

Online guckyfan

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Re: Mars Direct updated for the 21st Century
« Reply #44 on: 12/05/2017 07:04 AM »
I believe we already know a full year in uG on the ISS is not a showstopper.  I have no reason to think the 1/3rd G of Mars would be.  Potentially worthwhile sending up a well chained chimp and returning them first.

Or a volunteer.
I think there is time to work it out too. Supposing Mars does turn out to be a failure, eaten by space goat or something, we could just choose another direction like asteroid colonies and space habitats with full 1g spin gravity. I personally expect significant LEO space tourism before mars, if Elon really achieves the "747 of space" that the plan hinges on. BFS carrying 100 colonists probably doesn't happen until at least 3 or 4 synods and a lot of experience in cislunar space could happen before that, if this thing is flying regularly.

Point to point on earth may be before mass settlement on Mars. But I am very sure it will be after establishing a base on Mars. If no other reason it is overcoming regulatory hurdles taking time.

Offline Russel

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Re: Mars Direct updated for the 21st Century
« Reply #45 on: 12/05/2017 12:35 PM »
I believe we already know a full year in uG on the ISS is not a showstopper.  I have no reason to think the 1/3rd G of Mars would be.  Potentially worthwhile sending up a well chained chimp and returning them first.

Or a volunteer.

I think there is time to work it out too. Supposing Mars does turn out to be a failure, eaten by space goat or something, we could just choose another direction like asteroid colonies and space habitats with full 1g spin gravity. I personally expect significant LEO space tourism before mars, if Elon really achieves the "747 of space" that the plan hinges on. BFS carrying 100 colonists probably doesn't happen until at least 3 or 4 synods and a lot of experience in cislunar space could happen before that, if this thing is flying regularly.

I don't think we need a full g of spin gravity. My bet is that a lot of ill effects of zero or micro gravity go away with as little as 0.1g.  Enough for there to be a clear sense of "up". Musculoskeletal issues may be a different issue and I don't think we have enough data to know what "minimal" g is.

Also I remain skeptical of exposure of civilians to months of zero g and then subjecting them to 6gs, even for a minute. Case not closed imo.

- Its not that hard to generate a modest level of spin gravity.
- Its just not necessary to land humans on Mars with aerodynamic braking. Fully propulsive landing is entirely feasible. After all its only 4ish Km/s. Its not Earth.
« Last Edit: 12/05/2017 12:38 PM by Russel »

Online KelvinZero

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Re: Mars Direct updated for the 21st Century
« Reply #46 on: 12/05/2017 03:53 PM »
Just inserting another of my hobby horses. VR and expansive environments plus some sort of treadmill and elastic bands to simulate gravity. Or maybe an exoskeleton. I don't think it would be very heavy.

VR needs a bit more development, but this has the potential to keep you in better condition than just having gravity in a cramped cabin, and also satisfy psychological needs for entertainment and space, and could perhaps have practical purposes on Mars for teleoperation.
« Last Edit: 12/08/2017 08:53 PM by KelvinZero »