How Safe Is Travel To Mars

[ebort]

if a large asteriod or similar crashed into mars ..this might provide some added impetus to investigating the planet...it might (???) allso provide some shielding from the radiation by throwing large amounts of dust into orbit??<br /> <br />i'm sure that seeing up close and personal the results of a large scale asteriod strike on a non gaseous planet would warrent a manned trip even if no landing was made ?/

 

[mithridates]

Slightly off-topic, but how long in theory would a VASIMR-powered ship take to get to Venus compared to the three to four months to Mars? <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[qso1]

Probably two to three months. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[halman]

qso1,<br /><br />I read a glowing description of the VASIMR engine on a page from the Johnson Space Center, which sounds like it was written by a salesman. The engine definitely has a lot of promise, and it should be intensely funded, I believe. There was one aspect of utilization of the engine which was not covered, and that was the power source. Apparently, this engine is going to require a great deal of energy in the form of electricity, as it must first ionize a gas into a plasma, and, while containing the plasma magnetically, heat the plasma beyond its initial temperature, before injecting it into a magnetically shaped nozzle. All the magnetic containment fields will probably have to be generated with electromagnets, and the heating utilizes radio frequency exitation, as well as a cyclotron. These are energy intensive operations, which means that a lot of electricity is going have to be generated onboad the ship.<br /><br />What method is purposed for doing this? Could the plasma be heated in a fission pile, or does it have to be done with radio frequency exitation and a cyclotron? Even if a fission pile is on the ship, if the engine requires electricity, the pile will have to be used to generate steam, which would be used to turn turbines, which would generate the electricity. I would think that heating a propellant in the pile prior to ejecting it would be more efficient.<br /><br /> <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[qso1]

VASIMR was to have used radio frequency exitation to heat the plasma IIRC, and magnetic containment to contain the plasma which would not be containable by known materials. But as you pointed out, it sounds like it was written by a salesman and there are probably quite a few catches to developing a device with such promise. One catch of which is cost. A VASIMR based design will have to break the cost barrier if we are ever to see it in operation. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[halman]

qso1,<br /><br />You are correct that radio frequency exitation was to be used to heat the plasma, and magnetic containment would be used. What I am trying to figure out is where the energy to create the radio frequencies and power the electromagnets would come from. There is no mention of any kind of powerplant in the paper, even though energy demands would be considerable.<br /><br />I don't think that the paper addressed the possibility of using a fission pile to heat a working gas to exhuast speeds, which is about the most efficient way to utilize nuclear power in rocket propulsion that I am aware of. Simply put, water, hydrogen, methane, or some other substance is passed through a nuclear pile, absorbing heat energy and expanding. It is forced by the pressure of its expansion out of a nozzle which maximizes its exhuast velocity. Such an engine can only be used outside the atmosphere, as the exhuast gas will be radioactive. However, very high IsP is possible, and extended thrust periods compared to chemical rockets could also be acheived. However, the pile has to be seperated from the rest of the vehicle as far as possible, as well as being sheilded on the side facing the rest of the vehicle. This induces design problems, and weight could be a drawback. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[qso1]

I don't recall seeing where the electrical energy would come from either and as you mentioned, a pile would require separation from the habitable portion of the craft VASIMR type engines would really only be useful outside the atmosphere. I recall enormously high ISPs with VASIMR based propulsion systems. On the order of at least 100,000. I do not know if a fission pile can provide that kind of ISP for the reaction mass. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[ebort]

i reckon taking advantage of the rovers etc on mars (whilst they are still operational) might be one way of making the best of things....send an unmanned mission containing a shielded habitat lander and fuel supply spare parts etc...leave the fuel and lander and spares in orbit...drop the habitat onto the surface...(either as building blocks or some sort of compact basic expandable unit)...we can then use the rovers and support infrastructure to check on the habitat etc - in case of damage..if it's a write off ..no one has died..if it's ok then send the crew in a light weight capsule built for speed...able to expend all it's fuel on the out ward journey should help reduce the flight time..(all that fuel to get going and then to brake- more fuel faster transit time?--probably an optimum for that some where faster you go longer it takes to slow down...etc )<br /><br />crew can then use the lander parked in orbit to transit to the surface and use the habitat...<br /><br />the manned capsule can be refueled from the orbiting supply for the return journey...which has spare parts in case of damage break down etc...<br /><br />it's still all a bit "do or die" .which is why i think we need more infrastructure .. a little bit less "die hard/James Bond" etc and a bit more mundane long distance haulage thinking is needed ?? <br />if we build up the infrastructure we can do it with what we've got and build in safe gaurds --??<br /><br />could even send a stream of oxygen cylinders CO2 scrubbers food etc by ion drive capsules designed to drop their cargo from orbit....heck we got a car to the moon!! that's the sort of thing needed...

 

[JonClarke]

You were at the first CFM conference? I have just found a 2nd hand copy of the proceedings and ordered it (it is hard to get now and out of print, I have most of the others in that series except the last two) Did you present a paper? <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>

 

[qso1]

Ebort:<br />which is why i think we need more infrastructure...<br /><br />Me:<br />Thats for sure. We are going to one day have to realize that if we are to stay in the space exploration buz, we need a business minded infrastructure. Using rovers as you suggested would be a good idea if they are still operational in a decade or so. But this would also depend on us landing at the current rover sites assuming you were talking about utilizing the current rovers. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[thalion]

Re JonClarke:<br />All I'm trying to say is that there are real benefits to having higher-thrust propulsion. If we're serious about manned exploration of the Solar System, we're going to have to ditch the turboprop for the jet. Maybe not today, and maybe not tomorrow, but soon.

 

[vulture2]

>>I have just found a 2nd hand copy of the proceedings ..<br /><br />I must be discreet, however on page 173 you may find something of interest. Regrettably superconducting magnets (and electrostatics) for shielding were not considered. Also it is now clear that resistance exercise can reduce bone loss. Otherwise things have not changed all that much in all these years.<br /><br />I also agree with your point that many "questions" are depicted as "roadblocks" that must be "solved" before the first flight can proceed. Regretably NASA has chosen for the most part to fund only life science research that proposes to remove an obstacle in the "critical path roadmap " to an anticipated first manned Mars flight. This has had the rather predictable effect of forcing every researcher to claim the question he or she considers is a roadblock; if it's not, the proposal is unlikely to be funded. This policy seems shortsighted; the history of science is replete with cases in which basic research has been essential to real progress. Suppose we restricted the Hubble Space Telescope to research essential to a manned Mars mission?<br />

 

[JonClarke]

<i>All I'm trying to say is that there are real benefits to having higher-thrust propulsion. If we're serious about manned exploration of the Solar System, we're going to have to ditch the turboprop for the jet. Maybe not today, and maybe not tomorrow, but soon.</i><br /><br />Yes and no. The advantages are real, but so are the development costs. If the development costs are included in the mission costs then the mission becomes very much more expensive that it already is. Since cost, real and perceived, is (IMHO) the biggest obstacle for crewed missions to Mars then adding unnecessary development costs like advanced propulsion systems is a good way to ensure the mission won't happen. It is like waiting for jet engines before attempting the first trans-oceanic flights.<br /><br />It also means that the is held hostage to the uncertain development process of the advanced propulsion system. If the development proves more protracted or expensive than expected or encounters unexpectd problems of a fundamental nature, the mission is endangered. It's difficult enough developing a new chemical propulsion system, let alone some new nuclear electric, solar electric, or nuclear thermal system.<br /><br />Of course, if the advanced propulsion is available independently, then it should be carefully considered. But it should not be a requirement for the first missions. Once people are flying to Mars routinely then, I suggest faster means of transit will become attractive.<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>

 

[thalion]

<<Of course, if the advanced propulsion is available independently, then it should be carefully considered. But it should not be a requirement for the first missions. Once people are flying to Mars routinely then, I suggest faster means of transit will become attractive.>><br /><br />Fair enough. Though I should have been more specific, that is what I meant; developing novel propulsion before going to Mars for the first or second time would indeed be too expensive. But I still think that we need better propulsion (along with CATS, of course) for anything like long-term sustainability; shorter transit times or greater payloads could be invaluable.

 

[JonClarke]

Definitely! <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>