What's missing to get humans to Mars? - Orbit 11.28


wont be hard to make adjustments…a small ion thruster should be all that is needed to make the required changes…i would think… or some reaction wheels


That’s a lot of mass (and thus a lot of moment arm) to have to reorient, not sure an ion thruster would cut it. Plus you’d have to think of the mass design trade, is the fuel needed to reorient the spinning assembly less than the mass needed to have the panels rotate?


Good issues to consider… so maybe we will need 3/4 reaction wheels built into the Funnel.


So back to perchlorate for a moment… According to google’s wild, unsourced speculations, on Earth we are seeing around 100 mg of dust inhalation per day (I have no idea if that is realistic for a controlled habitat but we’ll roll with it). If the dust is 1% perchlorate, that would be a daily inhalation dose of 1 mg (1000 micrograms) per day. That’s less than half of the 2640 microg/day dose which begins to affect TSH levels. So at a glance, the numbers indicate we’re probably going to be just fine as far as thyroid function.

As for lung damage, the studies showing lung damage were using insanely high doses, more than 22.5 mg/kg (that would be 1,575,000 micrograms for the average 70 kg person). So we’re probably in the safe zone there too.

Even if EVAs cause a transiently increased exposure during ingress at the airlock, the residence time of perchlorate in the human body is only on the order of hours. So, we could just take the EVAs in shifts in order to allow people’s bodies time to clear and resume normal function. Meanwhile, the residence time for absorbed Iodine appears to be on the order of months,

The perchlorate levels are actually looking pretty tolerable.


Yeah I see 1% being stated for perchlorates in the martian soil… however, I think the dust may be at higher concentrations though I don’t have a reference, and I don’t really remember for sure but, 7% seems to be a number that surfaces from my thoughts. I will see if i can find a reference.

PS: Nope cant find anything :slight_smile: forget what i said :slight_smile:


This is an insightful and very well researched post, thank you.

Could you provide links to the studies about lung damage?

I think I’d like to turn this Mars perchlorate research into a Sci-Pod! If I started scripting this in a google doc, would folks be interested in helping with fact-checking and basic proofreading?


Lucky for you I save all these citations :slight_smile:

There’s a few grammar errors, it’s a study from china. It kind of scares to me think what kind of conditions people are working in over there if they’re testing the animals at such high levels.

Their results are kind of questionable in my opinion. I should think that breathing in more than a milligram of any salt all at once would cause serious lung damage (especially since they bypassed the filtering effect of the nose and throat). The saline they used as a control was 45 to 180 times less salty judging by my back of the envelope math.

I might enjoy doing a bit of proofreading, can’t promise I’ll be good at it though!

Wu, Feng-hong. et al. Biomarker expression in lung of rabbit with pulmonary fibrosis induced by ammonium perchlorate. DOI: 10.1177/0748233710386406. Toxicology and Industrial Health, 000(00) 1–7. 2010. ( TIH386406 1..7 )


One thing I didn’t find is any studies on whether extra Iodine really could be used as a treatment to perchlorate poisoning, since anyone on a goitrogen could simply have their dose reduced or discontinued instead. Also, ironically, too much Iodine can also cause hypothyroidism, so it’s one of those situations where the “treatment” could cause the disease… Still, it looks like there’s a pretty good range of doses where it could be effective.

This might make for a good future research project for some group with plans for Mars.


After thinking on it for a while, this might be research the State of California would want to fund, since giving people in perchlorate affected areas twice yearly Iodine supplements and having the forest service drop salt blocks for wildlife would be a lot cheaper than trying to remediate groundwater.

In the 1910s Dr. David Marine did something similar in schools near the Cleveland Clinic. Giving 2 grams sodium Iodide in syrup form twice yearly to 2000 school girls. The incidence of goiter dropped from 21.5% in the control group to 0.2% in the test group. I wish studies were so clear these days.

In the 1920s Dr. David Murray Cowie in Michigan lead a quest to stamp out goiters, we can basically thank him for Iodized salt in the US:

Markel, H. MD. When it Rains it Pours": Endemic Goiter, Iodized Salt, and David Murray Cowie, MD. Public Health, Then and Now. AJPH February 1987, Vol. 77, No. 2. Feb 1987. ( https://ajph.aphapublications.org/doi/pdf/10.2105/AJPH.77.2.219 )


Been thinking that there isn’t really any technical problems beyond our capacity to solve with very little effort… it’s just that we lack the critical mass of people with the will to work on, solve, build and launch and the people to pay for it…

How do you get those people?
We need an Economic, Political, Religious, or Existential need to get off this rock and settle on the most Earth like body in the solar system.

The America’s got colonized because initially there was money to be made doing so… Then Political competition and desire for a cut of those profits…Then mass migration due to religious persecution and other existential threats to the lives of various groups. And the technology to move people and goods across oceans rapidly advanced since there was massive economic incentives to speeding things up and thus a whole lot more people working on doing just that.

So to sum up. The one thing we lack is a really compelling business reason. Some thing of value … physical object or activity or something else entirely such that the cost of going is worth it.

I think Asteroid processing and Asteroid mining ship port of call and repair… and maybe even manufacturing could be that business reason.


Entry descent and landing has a high failure rate. To get it certified safe is going to be hard. One unlucky rock will cause catastrophe.


I’m absolutely agree with you. We can’t wait for 100% safe transportation system to Mars, because we can’t provide that even on Earth.

Virgil Ivan Grissom said once: “If we die we want people to accept it. We are in a risky business, and we hope that if anything happens to us, it will not delay the program. The conquest of space is worth the risk of life.” He and 2 others astronauts died in the Apollo 1 mission. The program was delayed a little, but not stopped - without it, we probably wouldn’t have even reached the Moon by now.

I hear a lot of exclamations about the fact that you can’t send people to Mars because it’s risky. And at the same time these people are support conscription (we have it). So why should i risk my life for some one piece of land on our planet, and i can’t risk my life for the future of all mankind as a whole? It’s silly.


We don’t need artificial gravity at all. Valeri Polyakov spent continuously 437 days in Mir station and he rose himself to his feet after landing - this is 2.4-3.1 times more than the required time travel to Mars and 2,64 times more than the necessary gravity. So that flown to Mars astronauts will be able to start working almost immediately upon arrival even without artificial gravity.

Or 4.5 month. And SpaceX even talk about less time, but i personally do not support the idea of even more time reduction. In what state astronauts return to Earth is not very important - on Earth they wil be waiting for a qualified medical staff. The main thing that they survived the overload at the reentry of the Earth atmosphere.

Mars have a lake under south pole several square miles across and at leas 3 feet deep. So if astronauts can reach it - it will provide them with almost unlimited water resources. But I think that for the first missions there will be enough and simple evaporation of water from the soil - even at the equator its content reaches 10%.

The previous version of the ship had retractable panels. Perhaps the new version will have them too.


I would like to see how he did it without help. But I did not find a video where he did that. Anyway suppose he did it. But stand up and be able to work is two different things. And probably he is an unique man.
So if we want to be intact on arrival to Mars we need to have at least partial “gravity” or drastically shorten the travel time.


options 1
partial “gravity” / full 1G “gravity” adds huge complexity and costs. But keeps crew in a proper condition. Plus we need better radiation shielding as well…costs, mass.
options 2
way way faster trip. Lets say under 60days or so. Less complexity(compared to options 1), less radiation. But huge amount of fuel. There is almost no room for cargo. Or need a new type of propulsion.
No matter which option we choose the first flights will still cost a lot (a LOT). But these are just numbers. And we all know that we are not in short supply of money itself. This is just a matter of adequate funding.
In short, we must change the way of thinking. And I am not talking about us. I am talking about common folks,
politicians, executives, etc etc.
So again …“What’s missing to get humans to Mars?”… motivation factor. Therefore, this is an unsolvable task for a government organizations. Can it be solved by a private company? Maybe cause they does not lack of motives. But they do not have enough money.


Latest mars satellite photos-




Here’s something small which could have a major impact on Interplanetary mission design.

The perdiem dose from Galactic Cosmic Radiation (GCR) during a Mars transit is around 1.84 mSv / day (about 90 chest xrays per day). If the EPA adopts a Threshold Model for radiation using a threshold of let’s say around 0.5 mSv / day, then the expected cancer risk associated with that mission’s dose would drop by 0.5/1.84 = 27%. If NASA follows suit and also adopts a threshold model, they could recalculate their cancer risks and subsequently reduce their calculated risk of long-term mission induced death (which is required not to go above 3%).

Potentially, this recalculation could be mission enabling, since “the radiation problem” is so commonly cited as holding back a Mars mission.

In case you want to know where I pulled that 0.5 mSv / day from, check out this chart from a long-term, low dose study of beagles [Fliedner et al] (the chart actually comes from a study done in the 60s, but the more primary sources are not easily available online):

(Note: in this study, the rad source was Gamma rays, which means 1 cGy = 1 cSv = 10 mSv)

Notice the 0 dose population died of old age, i.e. “natural causes” which was tumors about 70% of the time. The next dose group up is about the same. The tipping point where death rates start to increase from blood-cancers appears to be between 3.0-7.5 mSv/day. The EPA regularly tacks on a safety factor of 10x to account for population variability: thus we have 0.5 mSv/day. NASA astronauts are actually a lot healthier than the general population so NASA might even go higher with its threshold. That could potentially place the GCR dose below threshold, meaning it wouldn’t be expected to contribute at all to cancer.

News articles on this (not a one of which talks about space ::sigh::):

Nasa’s radiation guidance:
Huff, J.L. and Cucinotta, F.A. Chapter 7: Risk of Degenerative Tissue or Other Health Effects from Radiation Exposure. In: Human Health and Performance Risks of Space Exploration Missions. (Eds: Mcphee, J.C. & Charles J.B.) NASA LBJ Space Center. Houston, Texas. 2009. ( https://spaceradiation.jsc.nasa.gov/references/Ch7DegenRisks.pdf )
Curiosity’s radiation measurements:
Hassler, D.M. et al . (2013). Mars’ surface radiation environment measured with the Mars Science Laboratory’s Curiosity rover. Science 343 , 1244797. ( http://www.michaeleisen.org/blog/wp-content/uploads/2013/12/Science-2013-Hassler-science.1244797.pdf )
Long term animal study at low doses:
Fliedner T.M., Graessle D., Meineke V., Feinendegen L.E. Hemopoietic Response to Low Dose-Rates of Ionizing Radiation Shows Stem Cell Tolerance and Adaptation. Dose-Response 10:644-663. Oct. 9, 2012. ( Hemopoietic Response to Low Dose-Rates of Ionizing Radiation Shows Stem Cell Tolerance and Adaptation )


I was curious, so I did some analysis on the graph from the above post. There was a dog in that study in the 7.5 cGy/day group who took a cumulative dose of 151 Grays, lived 6.5 years in the study, and still didn’t die of a blood disease. That’s one tough Beagle.

You can see (if you squint) that the 3 mGy/day group lived about 11 months shorter than the 0 dose group but died of cancers at about the same rate (they actually had slightly fewer tumors). To reiterate, the GCR dose during a Mars transit is 1.84 mSv/day at solar maximum (best case). Worst case would be solar minimum which is about 2.5 times that or 4.6 mSv (for comparison to the beagles, in this case 1 Sv=1 Gy). Assuming Beagles are actually a good analog for people, it’s clear that we’ll be pretty close to the line on dose rate, and that’s not even counting solar flares and solar energetic particle events. We’ll still need to keep those transits short, and get under the dirt ASAP.


Not sure where to put this but this animation for a BFS Mars landing looks great.


I think dangers on trip to Mars due to lack of earths protective EM field are worried about too much.
Just take a look at this SpaceX prototype generator, charged particle radiation is the last of our worries. :joy: