Riding to Mars in a capsule?

[drwayne]

Unrelated tangent - I finally ordered a reprint of "Ignition!" the other day, it is another classic tome on the propulsion front....<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[danwoodard]

The actual radiation hazard is still unclear. The primary hazard from low-LET (linear energy transfer) rediation such as solar protons is cancer. With a total exposure of about 1 Gy for a 1.5 year mission, this would be an acceptable risk for a small group. Longer or multiple missions would ba problematic. <br /><br />The high-LET risk (primarily due to iron nucleii in cosmic rays) isn't easy to estimate, however. The flux is not as high; only about 20 rem/yr, and high-LET particles do not usually cause cancer, because they produce so much DNA damage that a cell is usually killed if it is traversed. This isn't a problem in most of the body; dead cells can be replaced. But in the brain, dead cells can't be replaced, so some irreverible degredation of brain function is to be expected. Probably this wouldn't be severe enough to cause noticable damage in 1 year (dose about .2Gy?). But experiments with animals show rather dramatic effects on the brain with more than a few grays of heavy ion radiation. And the usual shielding required to effectively reduce exposure (30 cm aluminum or about 2 meters of dirt) is probably beyond what is feasible for a spacecraft, particularly since it is not a situation that can be avoided with a small "storm shelter", galactic cosmic ray flux is constant. Shielding with consumables will become less effective as the consumables are used. Possibly a large superconducting magnet can be used to create an artificial magnetic field. However there is no research in this area at the moment.<br /> <br />I can see the first crew that had the chance to go simply putting up with the damage and accepting the risk, so perhaps for a "plant the flag" misison this is acceptable. But any serious plans for permanent colonization or even repreated visits would need a way to substantially reduce the exposure or after a few years we won't be in any condition to accomplish anything. <br /><br />Dan Woodard<br /><br /> />>>RADIATION<br /><br />An old d

 

[mattblack]

Good post!! Yes, the danger and the damage is mostly during the voyage. On the Moon and Mars, covering the Habitats with regolith would mostly do the trick. Though even on Mars the thin atmosphere gives enough protection to make it the third safest world to live on, after Titan which has an immense atmosphere. <div class="Discussion_UserSignature"> <p> </p><p>One Percent of Federal Funding For Space: America <strong><em><u>CAN</u></em></strong> Afford it!!  LEO is a <strong><em>Prison</em></strong> -- It's time for a <em><strong>JAILBREAK</strong></em>!!</p> </div>

 

[mikejz]

I was thinking for shelding of using the spent upper stage and a 'trash compactor' of sorts that would flatten the stage into something that could be used for sheilding.

 

[spacefire]

while using the Lander and the capsule thingy for extra living space during the trip to Mars seems like a good idea, I have a better one: NO CEV, dedicated ship to take astronauts to Mars, Lander launched separately to rendezvous in orbit. The ship would carry a re-entry capsule (lifeboat) with no life support of its own.<br />The crew would use a CTV to transfer to and from the space ship.<br />The spaceship would include at least two independent habitation modules, propulsion modules, and consumables modules (which could double as radiaton shielding), all launched separately and assembled in LEO.<br />when you go to Mars for the first time you want to take the avenue that ensues the greatest chance of success. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[spacester]

Great post! That assessment and those numbers are consistent with my understanding. Last time I tried, it was still hard to get definitive answers at any level on this subject. So this is encouraging . . .<br /><br />I did find one thing to quibble with, and to me it is significant:<br /><br /><font color="yellow">Shielding with consumables will become less effective as the consumables are used.</font><br /><br />My proposal for Man on Mars places a priority on long-term health. The mission is Settlement, not Exploration, so keeping the Settlers in prime condition on the voyage is an over-riding design criteria. Thus, the ship has to have spin-g and it has to have very, very good radiation shielding.<br /><br />I want the standard level of radiation shielding throughout the entire habitable volume to be at a level that most designs I’ve seen assign to the storm shelter area. I want the whole damn ship to be a storm shelter. As a design concept, the solution is simple; the problem of course is the huge mass involved.<br /><br />My research indicates that the best two shielding materials pound for pound are water and good old polyethylene, so the solution seems obvious: Surround the Settlers with plastic tanks full of water. When I’ve run the numbers, it looks like by the time you bring the entire volume to storm-shelter level, you’ve got enough mass of water to supply your need for so-called consumables without recycling. Thus, you can simply start off with pure fresh water and as you “consume” it, store the grey water and black water in tanks that also shield you. You arrive at Mars with tanks full of grey and black water, the crew goes to the surface and then the ship goes about the business of purifying the water while in Martian Orbit. You may or may not be willing to use this ship to return to Earth. Perhaps it stays on orbit as an orbital garden and refuge.<br /><br />Similarly, when talking about habitats for Moon and Mars, where most folks look at “several met <div class="Discussion_UserSignature"> </div>

 

[mattblack]

Only one thing wrong with your very good and very traditional idea, spacefire:<br /><br />Lack of $$$$$$ for this approach. Mars hardware will have to be as off-the-shelf as Nasa or whomever can make it. <br /><br />Also in regards to using consumables as radiation shielding, there would have to be a certain amount of polyethylene sheeting and water tankage built into the spacecraft structure where possible. The consumables would merely have a bonus shield effect. The polyethylene has been used quite effectively since the 1950's in nuclear subs. I'd also suggest looking at hydrocarbon-enhanced styrofoam and chloroflurocarbon impregnated petroleum gel. These alternatives would be far lighter than, say, an effective lead-salted "foamed" concrete. <div class="Discussion_UserSignature"> <p> </p><p>One Percent of Federal Funding For Space: America <strong><em><u>CAN</u></em></strong> Afford it!!  LEO is a <strong><em>Prison</em></strong> -- It's time for a <em><strong>JAILBREAK</strong></em>!!</p> </div>

 

[JonClarke]

There is aways more we can learn about radiation and its biological effects. However I would argue we do know enough to say that human missions are possible, including permanant bases through which people are rotated every 600 days or so. This does not mean that we don't need to do more work on the subject though.<br /><br />Colonisation through I agree, is a different kettle of fish. One of the things reasons we should go to Mars is to find out.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

Matt, just checking your numbers. You are definitely right about 3000 cubic feet being a bit tight for 6 people. That is only 85 m3. For missions of 6 months or more experience has shown you typically need a minimum of about 10 m of free livable volume per person, which equates to 30 m total pressurised volume, this means that need need 2 times as much volume as you have allowed.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

There is clever redunancy and... not so clever redundancy. Taking two of every major spacecraft element is not so clever, it means you throw away half your mission mass on redundant components that will probably not get used. A better way is to make sure that the redundant mission components are used in subsequent missions.<br /><br />For example, consider a semi-direct Mars mission. You have three spacecraft , a habitat lander (CL), a cargo module (CM) that includes an ascent stage and ISRU plant, and a Mars transfer vehicle (MTV) that includes a CEV in the nose. the CEV provides launch escape and direct entry to earth at the end of the mission. These are launched in the following sequence:<br /><br />Window 1: Launch of CL-1, HL-1 and MTV-1. CL-1 lands on Mars and manufactures consumables, the other two loiter in Mars orbit.<br /><br />Window 2: Launch of CL-2, HL-2, MTV-2. Crew 1 travels to Mars in MTV-2, once there they dock with HL-1 and land next to CL-1. At the end of the missson the ride the ascent stage and dock with MTV-1 and return to earth. meanwhile CL-2 has landed and begun preparing for crew 3, HL-2 and MTV-2 wait in Mars orbit for crew 2.<br /><br />Window 3: Launch of CL-3, HL-3, MTV-3. Crew 2 travels to Mars in MTV-3, once there they dock with HL-2 and land next to CL-2. At the end of the missson they ride the ascent stage and dock with MTV-2 and return to earth. meanwhile CL-3 has landed and begun preparing for crew 3, HL-3 and MTV-3 wait in Mars orbit for crew 3.<br /><br />This way you always have complete redundancy of major mission elements but every misison element is eventually used.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[mikejz]

Just wondering: Are we talking about Direct-Entry, or enter Mar's orbit and THEN seperate and land?

 

[mattblack]

All the more reason to build a bigger Mission Module (Bigelow inflatable?), or keep to a crew of four!<br /><br />I was also a bit conservative in my figure for the pressurised volume of various contemporary modules that a Mission Module could be based on: <br /><br />For a double-Spacehab the figures are -- Research double module, or RDM, provides 2,200 cubic ft. of pressurized volume. (Should be more without experiment racks).<br /><br />The ESA MPLM (Leonardo etc) has 1094 cubic ft.<br /><br />U.S. Node Modules have 2472 cubic ft.<br /><br />Example: CEV+MM(doub-Spacehab-based)+MSAM = 4200 cubic ft. habitable volume. (600+2200+1400= 4200). Or if an MPLM-based module is used -- 3000 cubic ft; just like I first estimated.<br /><br />**In 1997, I interviewed Shannon Lucid about her long stay on Mir and we talked about crew comfort for long missions. I asked her if the pressurised volume of a Space Shuttle (2625 cubic ft), along with a Spacelab or double Spacehab module would be enough for a crew of 6 to go to Mars (I was thinking about a double-Spacehab for a Mission Module). She said that it would probably be adequate room, providing the food was good, the toilet was reliable, and the crew were kept busy!<br /><br />Dr Lucid also said that during 18 day Shuttle missions with the big pressurised Labs, several of her colleagues had remarked that never once, with a crew of 7, did they feel cramped during the flight. In fact, jokes were sometimes cracked about how they wished they had enough fuel to light the engines again and GO SOMEWHERE!!! Mars would be good... <div class="Discussion_UserSignature"> <p> </p><p>One Percent of Federal Funding For Space: America <strong><em><u>CAN</u></em></strong> Afford it!!  LEO is a <strong><em>Prison</em></strong> -- It's time for a <em><strong>JAILBREAK</strong></em>!!</p> </div>

 

[JonClarke]

Sorry if I was not clear. In this scenario the CLs do a direct entry, the others enter Mars orbit. The crew transfers from the MTVs to the HLs which then land.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

The longer the mission the more space you need. Not just for stores and equipment, but personal space. After six months the volume levels off. Johnson and Pranke give 5 m3 as the tolerable limit for 6 months and more, 10 m3 as the performance limit, and 20 m3 as the optimal volume. All these are per person free volumes, actually presurised volume is three times this. So your 3000 cubic foot volume is actually below the tolerable limit for six people, your 4200 cubic foot volume a bit above, and at the performance limit for 4 people.<br /><br />Shannon Lucid had a lot more space during her stint on Mir over 100 m3 per person. This may have coloured her peception. Even an 18 day shuttle mission is very different from something 10 times longer. Survivable? Yes. Useful and healthy, almost certainly not. Remember this mission will be about productive work, not just survival. <br /><br />Jon<br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[mattblack]

I largely agree. If an inflatable Hab with its 5000+cubic ft volume isn't available, and "off the shelf" modules had to be used, then I'd opt for a module derived from doubling-up an ISS MPLM, or even going with a triple-Spacehab Module derivation. This would bring habitable volume up to around the 5000 cubic ft mark. Do-able, for sure. I also think we're underestimating the mental resilience of the Astronauts. The Salyut's, the Mir Core Module (and Zvezda) had slightly more than 3500 cubic ft of volume.<br /><br />In any case, staying within the 5-meter diameter of the HLV payload fairing would probably be the criteria. Also, in Zubrin's Mars Direct, they designed the classic "tuna-can" Hab Module for a crew of 4. With the CEV and Mars Lander in addition, that ought to be plenty. <br /><br />http://www.asi.org/adb/04/03/06/01/spacehab-module.html <div class="Discussion_UserSignature"> <p> </p><p>One Percent of Federal Funding For Space: America <strong><em><u>CAN</u></em></strong> Afford it!!  LEO is a <strong><em>Prison</em></strong> -- It's time for a <em><strong>JAILBREAK</strong></em>!!</p> </div>

 

[n_kitson]

Why do you need to stay within the faring diameter. Can't you just put, say, a 10m diameter fairing on?

 

[strandedonearth]

Too large of a fairing would increase the aerodynamic drag (for the atmospheric portion of the launch) as well as the stresses of MaxQ. Aside from that, I'm guessing (with my layman's opinion and info I've gathered on SDC) that a fairing too much bigger than the booster will lead to boundary layer separation and associated aerodynamic buffeting during the launch.

 

[JonClarke]

Volume of historic spacecraft used on long duration mission is quite large. Later DOS Salyuts had 100 m3 of pressurised volume per person, with a two person crew this equates to 16 m3 of free volume for each crew member. This is more than either of your options even with a four person crew. <br /><br />Zubrin's tuna can hab drawing is a bit misleading for an overal internal volume. It is 8 m in diameter, but does not specify a ceiling height or show external airlocks or storage space. If we assume 2.1 m ceilings, a lower deck with storage, airlock and workshop space the volume per person would be 17 m3.<br /><br />I was under the impression that the SDLV is to have a 7 or 8 m fairing. The 5 m fairing is just for the CLV. If you are going to use 5 m fairings this has big implications for your spacecraft configuration. Not bad implications but it does rule out some configurations - like Zubrin's tuna can, or the similar strcutres of DRMs 1-3<br /><br />Jon<br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[radarredux]

> <i><font color="yellow">Why do you need to stay within the faring diameter. Can't you just put, say, a 10m diameter fairing on?</font>/i><br /><br />Or use an inflatable habitat -- although, not very useful for entry into an atmosphere (at least in inflated mode).<br /><br />See http://www.bigelowaerospace.com/ for examples.</i>

 

[spacefire]

I just can't see ISRU being used for early manned Mars missions. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[radarredux]

> <i><font color="yellow">I just can't see ISRU being used for early manned Mars missions.</font>/i><br /><br />ESAS includes a Methane/LOX engine, a direct nod to ISRU on Mars. Send a seed stock of Hydrogen to Mars, combine it with carbon dioxide in Mars' atmosphere and get Methane and water. 1 ton of Hydrogen will generate 2 tons of Methand and 4.5 tons of water.<br /><br />I bet within 5 years there will be a call for proposal for a mini-Sabatier system to be included on a future Mars lander to test the process on Mars.</i>

 

[j05h]

>If you are going to use 5 m fairings this has big implications for your spacecraft configuration. <br /><br />Especially large implications for the VSE lunar lander, which will be quite a bit wider than 5m, even with the landing legs stowed. <br /><br />Note on the Bigelow inflatables: the diameter change is only about +100% after deploy. The base unit might be 4m in diameter and inflates to 8m. From what I can tell, the fabric layers are thick and don't fold flat. Even unflown, their modules are our best bet for habitats in space. <br /><br />Jjosh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[JonClarke]

The NASA DRM version 3.) had some concepts of a transhab within a partial rigid aeroshell. I am not sure how practical it is. If you are going to have a rigid aeroshell, why bother with an inflatable hab? If you have an inflatable hab, you might as well have an inflatable heat shield like a ballute.<br /><br />Mind you, I am not convinced of the advantage of using an inflatable hab anyway. I don't think it saves mass and it certainly increases complexity and work. I would rather stick with a rigid structure for most applications. But an infatable would be a useful way of creating extra volume for a growing Mars base.<br /><br />Jon<br /><br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

Without ISRU you are left with flag and footprints missions unless you go for simply colossal spacecraft or fleets of spacecraft. With ISRU you can do significant science and exploration for compartively modest masses.<br /><br />Almost every US Mars crewed mission study of the past 15 years has had some component of ISRU from the very beginning - Mars Direct, DRM versions 1.0-4.0, tand various others. It makes such a big difference to mission masses, or as Dobbins would say, mission logitics, that it be almost complete pointless not to have it.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[cuddlyrocket]

"1 ton of Hydrogen will generate 2 tons of Methane and 4.5 tons of water."<br /><br />That's a lot of water! The Mars Reference Mission shows a need for 10 tons of Methane, but only 7.6 tons of water for the mission.<br /><br />The surplus can be electrolysed, with the Oxygen being used for life support and/or oxidiser in the propellant (although a lot of this will come from electrolysing CO2), and the Hydrogen used to make more Methane etc.