Manned missions to Mars using existing launchers

[keermalec]

<p>There was a lot of discussion and research being done on this forum a few months back about sending humans to Mars using existing launchers. Most noteworthy was JO5H's "Mars, 9 tons at a time" thread. For my part, I was one of the sceptics, believing it was not possible to send humans in a safe manner using existing launchers' limited "throw capacity" to Mars.</p><p>Main hurdles we came up with was time of flight, on the one hand, believed by many to be limited to 6 months in space because of the effects of zero-g and galactic cosmic rays on the human crew. The other main argument against sending many light vehicles instead of a large, was that, according to the literature published by NASA and others, a typical 6-person vehicle would mass around 30 tons, or 5 tons per person.&nbsp;Considering the throw capacity of today's largest launcher is 8 tons to Mars, the limitations are obvious.</p><p>On another thread I was defending the idea of using continuous low thrust (ion drives) to send all that was not alive to Mars first, on long slow trips but with high efficiency (useful arrival mass/departure mass ratio) in order to reduce launch mass and cost.</p><p>Since then I have worked out the math and after starting again many many times I have come up with a hybrid but realistic solution where an ion drive space tug is used to raise the trans-Mars vehicle in Earth orbit, before it injects onto a transfer trajectory using chemical high thrust, dramatically increasing the payload sent to Mars. I would like to share this concept here with you, for comments and suggestions for improvement.</p><p>A Mars Heavy Transport Architecture</p><p>&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[scottb50]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>There was a lot of discussion and research being done on this forum a few months back about sending humans to Mars using existing launchers. Most noteworthy was JO5H's "Mars, 9 tons at a time" thread. For my part, I was one of the sceptics, believing it was not possible to send humans in a safe manner using existing launchers' limited "throw capacity" to Mars.Main hurdles we came up with was time of flight, on the one hand, believed by many to be limited to 6 months in space because of the effects of zero-g and galactic cosmic rays on the human crew. The other main argument against sending many light vehicles instead of a large, was that, according to the literature published by NASA and others, a typical 6-person vehicle would mass around 30 tons, or 5 tons per person.&nbsp;Considering the throw capacity of today's largest launcher is 8 tons to Mars, the limitations are obvious.On another thread I was defending the idea of using continuous low thrust (ion drives) to send all that was not alive to Mars first, on long slow trips but with high efficiency (useful arrival mass/departure mass ratio) in order to reduce launch mass and cost.Since then I have worked out the math and after starting again many many times I have come up with a hybrid but realistic solution where an ion drive space tug is used to raise the trans-Mars vehicle in Earth orbit, before it injects onto a transfer trajectory using chemical high thrust, dramatically increasing the payload sent to Mars. I would like to share this concept here with you, for comments and suggestions for improvement.A Mars Heavy Transport Architecture&nbsp;&nbsp; <br /> Posted by keermalec</DIV></p><p>Interesting and well researched. What I see as a problem though&nbsp; is depending on existing launch capabilities and seperate methods for people and cargo. While easily done and economical the ion drive would end up taking way more time and launch expense then it would saves. I see a use for ion drives enroute to Mars, but even there the contribution would probably not be worth the mass to get it into space to begin with.</p><p>What I see is 32,329 pounds to GTO for the Delta IV Heavy in 2011, roughly two launches for your six passengers. Since you would be leaving LEO, rather then the surface it would make more sense to use three launches, the first the outbound/return vehicle and landing/ascent vehicle, the second the supplies needed enroute and the third the crew and propellant needed to leave LEO, brake into LMO, descend to the surface, return to LMO and return to LEO.</p><p>With everything remaining in LEO for the next roundtrip a second trip could provide expanded surface structures and a larger crew with maybe two launches. This pre-supposes return to LEO and not a highspeed plunge to Earth and a vehicle that could economically do that, a simple up and back vehicle, not a multi-multi tasking Shuttle.</p><p>That this could even be done with expendables is my biggest question. As a one shot, plant the flag and go home mission it could probably be done, but to establish a base and keep it manned and supplied just makes no sense with current launchers. The same holds true with the so called "vision", a repeat of Apollo at the best then the costs preclude future expansion.</p><p>I would say 30 tons and 6 people for the first mission would be about right, but if the second mission can't take 12-15, or more, people no one will be willing to pay for it, been there done that.</p><p>The reality is propellant is cheap and engines exist that can use it now, it's how you put them together that makes the difference. First we need a TSTO system, a heavy lifter that can take an upper stage to a point it can reach LEO, return, refuel and do it again. The upper stage needs to be flexible enough to be broken up into individual Modules and re-used for various purposes. Finally a return vehicle that carries passengers to LEO and back, attached to the upper stage.</p><p>The upper stages, which are basically tanks with attached engines then become the building blocks for everything else. Refueled they could be used as Tugs, taking cargo or people to different locations. Drained of propellant they could be used to build Stations, Vehicles, Landers or virtually anything needed in Space.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[BrianSlee]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>First we need a TSTO system, a heavy lifter that can take an upper stage to a point it can reach LEO, return, refuel and do it again. </DIV></p><p>See rocket powered blimps under this forum heading.</p><p>Why not use this concept in lieu of the ion drive space tug.</p><p>Assuming this can be done how would it change the current calculations. i.e. given a 15% reduction in delta-v requirements to LEO and significant reductions in launch facilities cost, how much would it improve the concept?</p> <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[keermalec]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>First we need a TSTO system, a heavy lifter that can take an upper stage to a point it can reach LEO, return, refuel and do it again.

See rocket powered blimps under this forum heading.Why not use this concept in lieu of the ion drive space tug.Assuming this can be done how would it change the current calculations. i.e. given a 15% reduction in delta-v requirements to LEO and significant reductions in launch facilities cost, how much would it improve the concept? <br />Posted by BrianSlee</DIV></p><p>Developing a new launch capability that could place 30-40 tons in LEO in a single launch would effectively dramatically improve the feasibility of a mission to Mars. But&nbsp;developing this launcher&nbsp;would also dramatically increase the cost of&nbsp;the mission, and could very well be the showstopper for humans on Mars.</p><p>I was limiting myself to answering the question: can we go to Mars now, with only existing launchers and technology?</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[keermalec]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Interesting and well researched. What I see as a problem though&nbsp; is depending on existing launch capabilities and seperate methods for people and cargo. While easily done and economical the ion drive would end up taking way more time and launch expense then it would saves. I see a use for ion drives enroute to Mars, but even there the contribution would probably not be worth the mass to get it into space to begin with.</DIV></p><p>Actually cargo and people use exactly the same mode of transport from Earth orbit to Mars. Its just the orbit raising part around Earth which is different: people are carried to the departure orbit by a direct launch, whereas cargo is transported by slow ion drive. this is necessary to limit the time people spend in space.</p><p>The ion drive increases time but dramatically reduces initial mass in LEO. Without the 18-ton space tug you would either need a 78-ton chemical drive space tug or a launcher with 2.3x the current capacity of the Delta-IV Heavy, to send the same size payload to Mars.</p><p>The issue of what we do there once we get there is a critical one, and you do right to underline it: should we go just to say we have been there? Is the scientific excursion sufficiently valid to justify risking men's lives and billions of dollars? Or do we go to stay? I have not tried to answer this question as&nbsp;I believe it is more one for politicians and philosophers. I simply wanted to pinpoint what we can do today if we decide to do it, a sort state of the art for going to Mars.</p><p>&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[BrianSlee]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Developing a new launch capability that could place 30-40 tons in LEO in a single launch would effectively dramatically improve the feasibility of a mission to Mars. But&nbsp;developing this launcher&nbsp;would also dramatically increase the cost of&nbsp;the mission, and could very well be the showstopper for humans on Mars.</DIV></p><p>&nbsp;Not necessarily.&nbsp; Everything but the airframe is already in existence.&nbsp; And assuming a business model similar to the A380 would put the cost for each LTA system at about 500 million a copy.(I think I can do it for much less but thats what an A380 costs)</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I was limiting myself to answering the question: can we go to Mars now, with only existing launchers and technology?</DIV></p><p>LTA systems are not a new technology.&nbsp;This would simply be a new application of the technology</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The issue of what we do there once we get there is a critical one, and you do right to underline it: should we go just to say we have been there? Is the scientific excursion sufficiently valid to justify risking men's lives and billions of dollars? Or do we go to stay? I have not tried to answer this question as&nbsp;I believe it is more one for politicians and philosophers. I simply wanted to pinpoint what we can do today if we decide to do it, a sort state of the art for going to Mars.&nbsp; <br />Posted by keermalec</DIV><br /><br />I would risk my life to help make it happen and we need to get off this rock if we are going to survive in the long term.</p> <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[keermalec]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Not necessarily.&nbsp; Everything but the airframe is already in existence.&nbsp; And assuming a business model similar to the A380 would put the cost for each LTA system at about 500 million a copy.(I think I can do it for much less but thats what an A380 costs)LTA systems are not a new technology.&nbsp;This would simply be a new application of the technologyI would risk my life to help make it happen and we need to get off this rock if we are going to survive in the long term. <br />Posted by BrianSlee</DIV></p><p>By LTA do you mean Lighter Than Air? If so, I suppose you are referring to JP Aerospace's Orbital Spaceship concept which is, at the moment, unfortunately&nbsp;far from being implementable and so does not fall into the "existing technology" limitations I set myself.</p><p>The problem with "future technologies" is no-one can say which will become feasible and cost-effective first. Therefore planning on any of these does not tell us how and when to get to Mars. It is interesting but not practical speculation. Will you use the Orbital Spaceship, the space elevator, fusion propulsion, anti-gravity or teleportation?</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[BrianSlee]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>By LTA do you mean Lighter Than Air? If so, I suppose you are referring to JP Aerospace's Orbital Spaceship concept which is, at the moment, unfortunately&nbsp;far from being implementable and so does not fall into the "existing technology" limitations I set myself.The problem with "future technologies" is no-one can say which will become feasible and cost-effective first. Therefore planning on any of these does not tell us how and when to get to Mars. It is interesting but not practical speculation. Will you use the Orbital Spaceship, the space elevator, fusion propulsion, anti-gravity or teleportation?&nbsp; <br />Posted by keermalec</DIV><br /><br />keermalec,</p><p>&nbsp; Yes,&nbsp; LTA stands for Lighter Than Air.&nbsp; As for the J.P. Aerospace design the answer is no, I concur that they are not close enough to be considered a player, the closer analogy would be the Lockheed/Martin Skycat Program which&nbsp;has already been built.&nbsp;There are links to the program &nbsp;and video of some low level tests in the thread titled "rocket powered blimps" under "Space Science and Astronomy" in this forum section.&nbsp; Here is the part of the thread that talks about Skycat.</p><p>DARPA funded Lockheed to build the Skycat, which was&nbsp;part of a&nbsp;development program to provide DoD with a heavy lift capability.&nbsp; Read more here </p><p>&nbsp;</p><p><font color="#5574b9">http://en.wikipedia.org/wiki/Skycat</font></p><p>Skycat was defunded following what&nbsp;I believe (emphasis on believe) were successful low level handling and control tests.&nbsp; I was told by DARPA that this was a congressional decision *based on budget* and no reasons of a technical nature&nbsp;were offered upon further inquiry *which is not surprising* given the nature of the program.&nbsp;</p><p>here is some video</p><p><font color="#5574b9">http://www.youtube.com/watch?v=W3n5cUaG5fg</font></p> <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[keermalec]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>keermalec,&nbsp; Yes,&nbsp; LTA stands for Lighter Than Air.&nbsp; As for the J.P. Aerospace design the answer is no, I concur that they are not close enough to be considered a player, the closer analogy would be the Lockheed/Martin Skycat Program which&nbsp;has already been built.&nbsp;There are links to the program &nbsp;and video of some low level tests in the thread titled "rocket powered blimps" under "Space Science and Astronomy" in this forum section.&nbsp; Here is the part of the thread that talks about Skycat.DARPA funded Lockheed to build the Skycat, which was&nbsp;part of a&nbsp;development program to provide DoD with a heavy lift capability.&nbsp; Read more here &nbsp;http://en.wikipedia.org/wiki/SkycatSkycat was defunded following what&nbsp;I believe (emphasis on believe) were successful low level handling and control tests.&nbsp; I was told by DARPA that this was a congressional decision *based on budget* and no reasons of a technical nature&nbsp;were offered upon further inquiry *which is not surprising* given the nature of the program.&nbsp;here is some videohttp://www.youtube.com/watch?v=W3n5cUaG5fg <br />Posted by BrianSlee</DIV><br /><br />Thanks for the links, BrianSlee. Very impressive technology of which I wasn't aware.&nbsp;Concerning Mars though,&nbsp;it is not (yet) part of a viable&nbsp;space launching system.</p><p>&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[BrianSlee]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Thanks for the links, BrianSlee. Very impressive technology of which I wasn't aware.&nbsp;Concerning Mars though,&nbsp;it is not (yet) part of a viable&nbsp;space launching system.&nbsp;&nbsp; <br />Posted by keermalec</DIV><br /><br />keermalec,</p><p>I will admit that there is still work to be done,&nbsp;but keep your eyes peeled.&nbsp; It might happen pretty fast given how close I think we are to adapting the technology for practical use in this area and the utility it provides in many others.</p> <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[nimbus]

<p>This is just my unprofessional opinion, but we should start laying the groundwork for permanent settlement asap. &nbsp;Whether that means one compromise or another of building/resource gathering and science, or sending willing people on one way trips, is above me... But it seems to me that resource exploitation is the one thing that most allows everything else. &nbsp;We can do some science now (and certainly we would do a minimum of science to validate and prepare for a settlement/resource mission), but the bigger the original settlement and delay in initial production/mining/etc, the bigger the output once things do get going.</p><p>This would probably require or at least favor some sort of academic curiculum to prepare to be a space colonist.. &nbsp;I think the initial bottleneck is like the initial tooling cost in mass production.</p><p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The issue of what we do there once we get there is a critical one, and you do right to underline it: should we go just to say we have been there? Is the scientific excursion sufficiently valid to justify risking men's lives and billions of dollars? Or do we go to stay? I have not tried to answer this question as I believe it is more one for politicians and philosophers. I simply wanted to pinpoint what we can do today if we decide to do it, a sort state of the art for going to Mars. &nbsp; <br /> Posted by keermalec</DIV><br /></p> <div class="Discussion_UserSignature"> </div>

 

[keermalec]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>This is just my unprofessional opinion, but we should start laying the groundwork for permanent settlement asap. &nbsp;Whether that means one compromise or another of building/resource gathering and science, or sending willing people on one way trips, is above me... But it seems to me that resource exploitation is the one thing that most allows everything else. &nbsp;We can do some science now (and certainly we would do a minimum of science to validate and prepare for a settlement/resource mission), but the bigger the original settlement and delay in initial production/mining/etc, the bigger the output once things do get going.This would probably require or at least favor some sort of academic curiculum to prepare to be a space colonist.. &nbsp;I think the initial bottleneck is like the initial tooling cost in mass production. <br /> Posted by nimbus</DIV></p><p>Nimbus, I perfectly agree with you when you say that development of in-situ ressources utilization is critical for the long term vision of humans on Mars. Producing water will save mass transported from Earth's gravity well, developing building methods using local materials will enhance comfort and security for the surface team, and mastering the production of food from martian soil will both reduce mass brought from Earth and erase the time limit on human presence on the Red Planet.</p><p>If people were crazy enough to want to live on Mars without coming back, as you mention, mission costs would also be substantially lowered even more. Such "colonists" could therefore be paid a handsome amount.</p><p>Assuming one Standard Mars Aeroshell for the Mars trip, another for landing, a third for surface equipment, a fourth for the ascent vehicle, and a fifth for the return vehicle, that's 5x18 tons of hardware for 3 people to Mars and back. </p><p>Quick cost estimate: assuming 100 million USD /ton (the cost of a typical high cost ISS module), the overall cost of a mission could be around 9 billion for the SMAs + 4.7 billion for the Orbital Transfer Tug + 1.5 billion for launches (4 Delta IV Heavies, 4 Soyuz 11A511U for OTT tanks and two more Soyuz for the crew) + 1 billion for modifying the upper stage to enable cryogenic coolling =&nbsp; 16.2 billion USD in 1999 dollars. That would be around 20.8 billion USD in 2008 dollars assuming no greater development costs/ton than for an ISS module (this is debatable). Add 20% contingency provisions and we're at 25 billion USD.</p><p>If we were to scrap the return hardware the cost would come down by some 27%... (two SMAs less) to about 18 billion USD per 3 persons including contingency...</p><p>This is substantially less than previous manned Mars schemes because of the non-development of a new heavy lift capability (remember the Ares V is estimated to cost 40 billion USD in R&D). Using existing commercial launchers is yet another key to reducing the cost of a mission to Mars.</p><p>&nbsp;</p><p>&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[nimbus]

<p>Well, payment in money would only serve them so much, considering where they're going &nbsp;It's a crazy idea, but apparently not that crazy. I would definitely go myself, if there was some guarantee what I did wasn't in vain.</p><p>If only there was a way to get this idea presented to the public without setting off their disbelief.. It's really not that far out after all, considering the precedents here on Earth a few centuries ago. &nbsp;There just needs to be an appealing enough goal within reach to sell to the public to overcome the initial inertia. I have to admit I don't know what else to add to the topic without derailing it further &nbsp; Reducing the payload fraction with a one way trip formula is the only suggestion I can think of... I really don't know enough about propulsion or insulation or orbital mechanics (except for the hohmann method). </p><p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Nimbus, I perfectly agree with you when you say that development of in-situ ressources utilization is critical for the long term vision of humans on Mars. Producing water will save mass transported from Earth's gravity well, developing building methods using local materials will enhance comfort and security for the surface team, and mastering the production of food from martian soil will both reduce mass brought from Earth and erase the time limit on human presence on the Red Planet.If people were crazy enough to want to live on Mars without coming back, as you mention, mission costs would also be substantially lowered even more. Such "colonists" could therefore be paid a handsome amount.Assuming one Standard Mars Aeroshell for the Mars trip, another for landing, a third for surface equipment, a fourth for the ascent vehicle, and a fifth for the return vehicle, that's 5x18 tons of hardware for 3 people to Mars and back. Quick cost estimate: assuming 100 million USD /ton (the cost of a typical high cost ISS module), the overall cost of a mission could be around 9 billion for the SMAs + 4.7 billion for the Orbital Transfer Tug + 1.5 billion for launches (4 Delta IV Heavies, 4 Soyuz 11A511U for OTT tanks and two more Soyuz for the crew) + 1 billion for modifying the upper stage to enable cryogenic coolling =&nbsp; 16.2 billion USD in 1999 dollars. That would be around 20.8 billion USD in 2008 dollars assuming no greater development costs/ton than for an ISS module (this is debatable). Add 20% contingency provisions and we're at 25 billion USD.If we were to scrap the return hardware the cost would come down by some 27%... (two SMAs less) to about 18 billion USD per 3 persons including contingency...This is substantially less than previous manned Mars schemes because of the non-development of a new heavy lift capability (remember the Ares V is estimated to cost 40 billion USD in R&D). Using existing commercial launchers is yet another key to reducing the cost of a mission to Mars.&nbsp;&nbsp;&nbsp; <br /> Posted by keermalec</DIV><br /></p> <div class="Discussion_UserSignature"> </div>

 

[keermalec]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, payment in money would only serve them so much, considering where they're going &nbsp;It's a crazy idea, but apparently not that crazy. I would definitely go myself, if there was some guarantee what I did wasn't in vain.If only there was a way to get this idea presented to the public without setting off their disbelief.. It's really not that far out after all, considering the precedents here on Earth a few centuries ago. &nbsp;There just needs to be an appealing enough goal within reach to sell to the public to overcome the initial inertia. I have to admit I don't know what else to add to the topic without derailing it further &nbsp; Reducing the payload fraction with a one way trip formula is the only suggestion I can think of... I really don't know enough about propulsion or insulation or orbital mechanics (except for the hohmann method). <br />Posted by nimbus</DIV></p><p>Very, very interesting article, Nimbus. I had no idea people could be that crazy but then again, that's exactly what they were doing 500 years back...</p><p>Personally I am not&nbsp;especially in favour of sending people on a one-way trip to Mars, though I would respect anyone's decision to do so. Like I said before, that is an issue for politicians and philosophers and I like to see myself as a technician. I&nbsp;run a construction company and I'm used to just getting things done.</p><p>More realistically, there should be several successful reconnaissance missions first to validate the technology and allow better cost and security planning for would-be colonists.</p><p>If people are ready to travel 6 months in a cramped manner, they may travel in the descent vehicle itself, the habitat part of which would mass between 4 and 8.9 tons (aeroshell minus lander mass). For comparison: the Apollo habitat (ascent vehicle) massed 2.2 tons for 3 persons.</p><p>If the descent vehicle were dual use, one could reduce the total mission mass by one full SMA.</p><p>In an optimal scenario then, where the crew travels in the descent vehicle which doubles up as an ascent vehicle too (after in-situ refueling) a round trip for 3 persons would involve:</p><p>3 SMAs (54 tons of hardware)<br />3 OTT jettisoneable tanks (21 tons)<br />1 OTT (11 tons)<br />1 crew transfer vehicle to departure orbit (14 tons)&nbsp; <br />------------------------<br />Total hardware: 100 tons</p><p>Required launches:</p><p>4 heavy (18-25 tons to LEO)<br />4 medium (7 tons to LEO)</p><p>&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[nimbus]

<p><font size="2">Keermalec, using your plan, would it be possible for the return trip TOF to be either 6 or 9 months, or only 6 months? &nbsp;I assume the mention (in your plan's pdf) of avoiding crew exposure to space transit longer than 6mos on the way to Mars implies you only consider 6mo return trips..</font></p><p><font size="2">Is it not possible with current hardware to return in 9 months? &nbsp;&nbsp;</font></p><p><font size="2">&nbsp;edit- The above question gets stranger and stranger the more I learn about orbital mechanics between mars and earth (I knew nothing when I originaly posted this). &nbsp;I ask because someone on another forum is telling me this:</font></p><p><br /><<<br /><font size="2"><em>The United States does not currently have a rocket system that is big enough to carry a crew of 2 or 3 to Mars via the "short route" and come back via the "long route" if necessary. There are only certain times of the year where a take off time scheduled to arrive at the shortest possible route. It still takes a good 6 months to get there on the shortest route possible and 9 to 10 months on the longer route. The Ares V/VI series wouldn't be adequite either. The technology I refer to does not exist yet or we'd be there already.<br /><br />By the time it takes a spacecraft (by current our current technology standpoint = liquid fueled) to get to Mars via the shortest possible route (distance) due to the different orbits that the Earth and Mars have, coming home by the exact same short route may not be possible. Earth and Mars have orbits that are more egg shaped at times than perfect circles around the Sun. You also need to time your take off and return to avoid getting anywhere near the Sun.<br /><br />I'm talking scientific logistics here:<br /><br />1) Fuel to get to Mars via the shortest possible route <br />2) Enough area onboard to carry enough water or a water/urine filtration system to get them there & back<br />3) Enough area onboard to carry enough food or food producing systems to get them there and back<br />4) Enough fuel and a big enough spacecraft to carry it to take them home via the shortest route possible.<br /><br />Shooting off "slow poke" supplies in advance in Low Earth Orbit might be a good idea. But why not just use the ISS? It's not colmpleted yet but that is one of the ISS objectives. The ISS is a good start as a relay station for a Mars expedition.<br /><br />Saturn V technology depended on the fact that the mother-vehicle is able to maintain it's E while orbiting the planet while the men and exploration vehicle are on the planet's surface. Once the men and exploration craft have rendezvoused with the mother-vessel, they would have to do a controlled burn for the return at precise time to return to Earth. For Mars you's have to do that and then return to earth. With solid/liquid fuel technology we're talinking one HUGE honkin' arsed sized mother-vehicle.<br /><br />The ISS is currently being built in stages to provide a long-term Earth orbiting space station that would essentially be a gigantic scientific SkyLab. It was/is never intended to be a transplanetary space vehicle, it was originally intended to be a very large modular space science laboratory and have docking facilities for both manned and (future) drone spacecraft. It has been, however, considered a possible future relay station for space exploration vehicles, i.e.: blast off from Earth---go to the ISS--get into pre-assembled craft from there and then depart there for other planets.<br /><br />The problem still exists for the big four: Oxygen, water, food, and fuel. &nbsp;<br /><br />It has been often debated by scientists if a solid/liquid fueled rocket/space shuttle could dock with thei ISS, deliver it's crew and supplies, and then depart for mars in a pre-assembled--pre-supplied space vehicle that was NUCLEAR powered...eliminating the need for liquid fueled engines and speeding up the travel time over liquid fueled rockets. Also cutting down substancially on the amount of water, oxygen and fuel a common liquid fueled rocket would require.</em></font> <br /> /> />&nbsp;</p><p><font size="2">It sounded really odd the first time I read it.. The only reasons I can think of that would disallow going via 6 month trajectory and returning via 9 month trajectory, is if the 9 month trajectory requires more fuel than the 6 month one. &nbsp;And/or if the next 6 month return window is so much later after arrival that it means the mission requires more human supplies than any existing rockets can carry. &nbsp;</font></p><p><font size="2">I'd read the old 'Mars 9t at a time', so it sounded strange that there were no rockets available today that could go there and back safely for human passengers. &nbsp;But then there's the "point" that no rocket can go in 6mo and return in 9 "<em>if it has to"</em></font><font size="2"> &nbsp;What is that supposed to mean?<br />Some of the other things in the above quote sound wrong, but they don't really matter.<br /></font></p> <div class="Discussion_UserSignature"> </div>

 

[keermalec]

<p>Hi Nimbus, the post you quote is correct on several points but the author seems to be quite dogmatic about a number of things.</p><p>First of all, to set things straight: a 9-month trip to Mars is possible and will require LESS propellant than a 6-month trip. As you correctly pointed out, I did not consider 9-month trips for crew health reasons and that is the only reason 9-month trips are missingh from my tables.</p><p><font size="2">When the author states that a rocket can go in 6mo and return in 9 "<em>if it has to"</em> he is talking about propellant load I believe.</font></p><p><font size="2">I use the awesome (and free for non-commercial use) Jaqar software to calculate C3s.</font></p> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[nimbus]

Thank you.<br /> <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

Hey I'm back! It's been too long. :mrgreen:

I'm glad to see you have not rested when it comes to the ideas threshed out on the old thread, "Mars, 9 tons at a time". BTW, I can't seem to find that thread anymore, even when I click on your link. Did the thread go poof? It would be a shame for all that interesting work to just disappear.

I don't have time right this moment to examine your new architecture, but I promise to get to it soon and then give you some feedback.

 

[gunsandrockets]

A Mars Heavy Transport Architecture

Oh, no! dead link

I would really like to see the proposal. Anyone have a copy?

 

[nimbus]

I'd gladly send you a copy but the HDD with it crashed.. I'll appreciate a new copy if Keermalec still has one