Author Topic: Can we get to Mars using existing rockets?  (Read 15263 times)

Offline mmeijeri

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Re: Can we get to Mars using existing rockets?
« Reply #40 on: 01/26/2011 02:45 pm »
But I guess I just don't see the point. Mars does have an atmosphere, and while it might not be sufficient to get a heavy lander to subsonic speeds, you can still let significant deceleration work out of it.

Agreed. Fully propulsive landings are mainly useful as a reference point to compare other solutions with. It's what we could do if we had to land a heavy payload on Mars in a hurry. Or one thing we could do if we wanted to stimulate development of cheap commercial lift by buying lots of propellant in orbit.
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Offline OpsAnalyst

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Re: Can we get to Mars using existing rockets?
« Reply #41 on: 01/26/2011 03:10 pm »
Radiation. Crew. Long pole in the tent.

Offline Robotbeat

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Re: Can we get to Mars using existing rockets?
« Reply #42 on: 01/26/2011 03:31 pm »
Radiation. Crew. Long pole in the tent.
I disagree.

Radiation in Mars orbit is about 440mSv per year, as measured by Odyssey (radiation on the surface will be much lower than that, less than radiation on ISS). http://www.jpl.nasa.gov/releases/2003/34.cfm
Note that this is below 500 mSv annual limit to the blood-forming organs set by the NCRP (intended to limit the risk of cancer to an acceptable level).

This compares to about 260 mSv for the background radiation of parts of Ramsar, Iran.
"Inhabitants of Ramsar have lived for many generations in these high background areas. Cytogenetic studies show no significant differences between people in the high background compared to people in normal background areas." http://www.ncbi.nlm.nih.gov/pubmed/11769138
(Ssome folks in Ramsar, Iran receive an annual equivalent dose greater than would be received annually almost anywhere on the surface of Mars... http://www.solarstorms.org/MarsDosages.html assuming you like hanging around naked on the Martian surface. And those Iranians seem to live healthy lives.)


So, the annual dosage isn't far beyond what can be very well tolerated by humans on Earth. What about acute radiation from solar particle events?

This slide is very interesting for many reasons... (BTW, 1 cSv = 10 mSv)
http://www.bioedonline.org/slides/slide01.cfm?tk=56&dpg=13
(attached below for convenience)

In other words, as long as the astronauts are inside a spacecraft and not just in a spacesuit, even an exceptionally intense solar particle event stays well below even a significant chance of vomiting, let alone a significant chance of death--note the vertical scale is logarithmic. And by retreating to a well-shielded shelter during solar particle events--which are forecastable--astronauts can significantly reduce their total mission dose... simply being between the water (or propellant) tank and the Sun would work for these events (though it's a little more complicated than that because the radiation can be directed via the solar magnetic field, but that works to a zeroth order guess). A Bigelow-type module for such a trip would easily have at least the equivalent radiation protection as 30 grams/cm^2 of Aluminum (the blue line in that graph) (especially if you took refuge in the core).

And if you can shield against solar radiation to the extent it becomes negligible (by using an inflatable style module and placing supplies between the crew and the Sun) compared to cosmic rays, arranging the trip during solar maximum would mean (because of the stronger solar magnetic field repulsing galactic radiation) an even lower total radiation dose.

And this is all without even touching any drugs or other treatments which can possibly reduce the effects of both long-term and acute exposure (there are some drugs that are especially promising for acute exposure).
« Last Edit: 01/26/2011 06:35 pm by Robotbeat »
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Offline DarkenedOne

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Re: Can we get to Mars using existing rockets?
« Reply #43 on: 01/27/2011 11:22 pm »
Radiation. Crew. Long pole in the tent.
I disagree.

Radiation in Mars orbit is about 440mSv per year, as measured by Odyssey (radiation on the surface will be much lower than that, less than radiation on ISS). http://www.jpl.nasa.gov/releases/2003/34.cfm
Note that this is below 500 mSv annual limit to the blood-forming organs set by the NCRP (intended to limit the risk of cancer to an acceptable level).

This compares to about 260 mSv for the background radiation of parts of Ramsar, Iran.
"Inhabitants of Ramsar have lived for many generations in these high background areas. Cytogenetic studies show no significant differences between people in the high background compared to people in normal background areas." http://www.ncbi.nlm.nih.gov/pubmed/11769138
(Ssome folks in Ramsar, Iran receive an annual equivalent dose greater than would be received annually almost anywhere on the surface of Mars... http://www.solarstorms.org/MarsDosages.html assuming you like hanging around naked on the Martian surface. And those Iranians seem to live healthy lives.)


So, the annual dosage isn't far beyond what can be very well tolerated by humans on Earth. What about acute radiation from solar particle events?

This slide is very interesting for many reasons... (BTW, 1 cSv = 10 mSv)
http://www.bioedonline.org/slides/slide01.cfm?tk=56&dpg=13
(attached below for convenience)

In other words, as long as the astronauts are inside a spacecraft and not just in a spacesuit, even an exceptionally intense solar particle event stays well below even a significant chance of vomiting, let alone a significant chance of death--note the vertical scale is logarithmic. And by retreating to a well-shielded shelter during solar particle events--which are forecastable--astronauts can significantly reduce their total mission dose... simply being between the water (or propellant) tank and the Sun would work for these events (though it's a little more complicated than that because the radiation can be directed via the solar magnetic field, but that works to a zeroth order guess). A Bigelow-type module for such a trip would easily have at least the equivalent radiation protection as 30 grams/cm^2 of Aluminum (the blue line in that graph) (especially if you took refuge in the core).

And if you can shield against solar radiation to the extent it becomes negligible (by using an inflatable style module and placing supplies between the crew and the Sun) compared to cosmic rays, arranging the trip during solar maximum would mean (because of the stronger solar magnetic field repulsing galactic radiation) an even lower total radiation dose.

And this is all without even touching any drugs or other treatments which can possibly reduce the effects of both long-term and acute exposure (there are some drugs that are especially promising for acute exposure).

I think the radiation on the surrace could be solved with simple excavation technology.  Not to long ago NASA partnered with Caterpiller in order to create a lunar construction truck that would be remotely controlled.  What you could do is essentially use dirt from the landing site to create a very effective and rather inexpensive shield against all types of radiation and micrometorities.  Sand and dirt on Earth has a halving thinkness of about 3.5 inches.  Assuming the sand on Mars and the Moon has similiar properities very effective radiation shielding is possible.

Offline Robotbeat

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Re: Can we get to Mars using existing rockets?
« Reply #44 on: 01/27/2011 11:46 pm »
Radiation on the surface isn't really a problem. Folks in Ramsar, Iran get more radiation than that, and they're healthy. But, as you said, you have lots of shielding material readily available. The easiest way to do it would be a small shovel (which you'd already probably have for scientific uses) and a whole bunch of bags to shovel Martian soil into. Place the sandbags on top of your hab, and voila! Radiation dosage, already low, is halved. I suppose you could just heap dirt up there without even any bags, if it was flat.

Anyway, radiation on the Martian surface is not a problem (as long as you aren't on Olympus Mons).
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Patchouli

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Re: Can we get to Mars using existing rockets?
« Reply #45 on: 01/28/2011 01:41 am »
With the delays in SDLV and possibly no budgeting, can we use existing launch vehicles without major upgrades to design, launch, and assemble in space, vehicles and equipment to get to Mars?  If so, what launch vehicles? and how do you think we could do it? 

The Delta IV-H can be upgraded to 48T with relatively speaking minor upgrades and existing facilities
http://www.astronautix.com/lvs/delde48t.htm

It has options all the way to 70T existing tooling and 100T with tooling changes.
http://www.astronautix.com/fam/deltaiv.htm

Looking at the changes 40T out of the D4H should be low hanging fruit well within budget if there is no SDLV.
Actually with no SDLV even the more insane EELV upgrades likely could be afforded with money left over for Falcon X.
Also F9-H with Raptor should have an IMLEO payload in excess of 40,000Kg.
« Last Edit: 01/28/2011 01:43 am by Patchouli »

Offline DarkenedOne

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Re: Can we get to Mars using existing rockets?
« Reply #46 on: 01/28/2011 02:23 am »
Radiation on the surface isn't really a problem. Folks in Ramsar, Iran get more radiation than that, and they're healthy. But, as you said, you have lots of shielding material readily available. The easiest way to do it would be a small shovel (which you'd already probably have for scientific uses) and a whole bunch of bags to shovel Martian soil into. Place the sandbags on top of your hab, and voila! Radiation dosage, already low, is halved. I suppose you could just heap dirt up there without even any bags, if it was flat.

Anyway, radiation on the Martian surface is not a problem (as long as you aren't on Olympus Mons).

Look I here you and I think your right, but it is NASA we are talking about here.

The thing about radiation is that too much radiation will kill you fast, but small amounts of radiation over time will put you at risk for cancer. 

I highly doubt that NASA is going to take significant risks with radiation.

Offline Robotbeat

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Re: Can we get to Mars using existing rockets?
« Reply #47 on: 01/28/2011 05:19 pm »
Radiation on the surface isn't really a problem. Folks in Ramsar, Iran get more radiation than that, and they're healthy. But, as you said, you have lots of shielding material readily available. The easiest way to do it would be a small shovel (which you'd already probably have for scientific uses) and a whole bunch of bags to shovel Martian soil into. Place the sandbags on top of your hab, and voila! Radiation dosage, already low, is halved. I suppose you could just heap dirt up there without even any bags, if it was flat.

Anyway, radiation on the Martian surface is not a problem (as long as you aren't on Olympus Mons).

Look I here you and I think your right, but it is NASA we are talking about here.

The thing about radiation is that too much radiation will kill you fast, but small amounts of radiation over time will put you at risk for cancer. 

I highly doubt that NASA is going to take significant risks with radiation.
The risks of radiation exposure are not greater than the other risks of spaceflight.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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