Could the DC-X be a possible Mars lander?

[willpittenger]

I was reading The future of the DC-X in Wikipedia's DC-X article. It claims that DC-X might make a good Martian lander. Any comments?<br /><br />Also, I see in the article they were talking about adding a fifth leg (one failed to extend once). I think simpler would be better. How about fixed legs? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[qso1]

IMO, a DC-X derivitive is an excellent candidate for a mars lander except that payload will be severely limited since the vehicle will have to carry mostly propellant.<br /><br />I think a two stage lander would be the ideal choice for initial landings and establishment of an outpost or base.<br /><br />An SSTO (DC-X derived) could then serve as the primary means of crew transport to and from the martian surface once a base has been established. This will still require a propellant infrastructure to service the DC-X derivative in martian orbit and on the surface.<br /><br />But then, anything mars will involve more than what is generally anticipated or proposed in mars mission plans. <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>

 

[willpittenger]

I am sure that Zupin would suggest using regolith for fuel. Would such generators be able to produce fuel at a quick enough rate? Also, I have a feeling that since sending more fuel to Mars is expensive, the orbital refueling station won't happen. If we refuel the SSTO, it will be on the surface with Zupin's regolith fuel.<br /><br />Fortunately, we are starting to see more efficient ways of storing hydrogen. One older technology was to put the hydrogen into a slush state. The slush moves around less than liquid hydrogen and is probably more compact than either that or compressed gas.<br /><br />Another system proposed for fuel cell cars that might or might not be adaptable for rocket fuel would be a system that I think was based on a powder. It absorbed hydrogen like a sponge. To get the hydrogen out, you change the temperature. I don't recall if you heated or cooled it, but it was one of them. The real question would be how fast it can release. Rocket engines are thirsty. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[JonClarke]

"Also, I see in the article they were talking about adding a fifth leg (one failed to extend once)."<br /><br />With five legs if you lose one you won't fall over.<br /><br />"I think simpler would be better. How about fixed legs?"<br /><br />Fixed legs will burn off during atmospheric braking.<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]

"IMO, a DC-X derivitive is an excellent candidate for a mars lander except that payload will be severely limited since the vehicle will have to carry mostly propellant. "<br /><br />Remember that SSTO is much easier on Mars than on earth, orbital velocity is only 5 km/s.<br /><br />"An SSTO (DC-X derived) could then serve as the primary means of crew transport to and from the martian surface once a base has been established. This will still require a propellant infrastructure to service the DC-X derivative in martian orbit and on the surface."<br /><br />Surface yes, but why in orbit?<br /><br />"But then, anything mars will involve more than what is generally anticipated or proposed in mars mission plans."<br /><br />Meaning?<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]

"I am sure that Zupin would suggest using regolith for fuel. Would such generators be able to produce fuel at a quick enough rate? Also, I have a feeling that since sending more fuel to Mars is expensive, the orbital refueling station won't happen. If we refuel the SSTO, it will be on the surface with Zupin's regolith fuel. "<br /><br />Zubrin (and others before him) suggested reacting atmospheric CO2 with imported hydrogen to produce methane and LOX. No regolith involved. of course we now know that there is enough water in much of the Martian regolith to make hydrogen etraction feasible.<br /><br />"Fortunately, we are starting to see more efficient ways of storing hydrogen. One older technology was to put the hydrogen into a slush state. The slush moves around less than liquid hydrogen and is probably more compact than either that or compressed gas. "<br /><br />You can jellify hydrogen by mixing in a little methane. this recuces boil off considerably, I believe.<br /><br />"Another system proposed for fuel cell cars that might or might not be adaptable for rocket fuel would be a system that I think was based on a powder. It absorbed hydrogen like a sponge. To get the hydrogen out, you change the temperature. I don't recall if you heated or cooled it, but it was one of them. The real question would be how fast it can release. Rocket engines are thirsty."<br /><br />Indeed they are/ the other problem is that metal hydrides are heavy. For rockets it's tanks for nothing.<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>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>For rockets it's tanks for nothing.<p><hr /></p></p></blockquote><br />Tanks for cryo-materials are heavy. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p><blockquote><font class="small">In reply to:</font><hr /><p>Also, I see in the article they were talking about adding a fifth leg (one failed to extend once).<p><hr /></p></p></blockquote><br />With five legs if you lose one you won't fall over.<p><hr /></p></p></blockquote><br />I know that. However, the reason Boeing was able to push ETOPS through the FAA rule book was because the more engines a plane had, the more engines could fail. In fact, that was why Lindberg insisted on only one engine for the Spirit of St. Louis. With a lander, the more retractable legs you have, the more things you have to fail.<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><blockquote><font class="small">In reply to:</font><hr /><p>I think simpler would be better. How about fixed legs?<p><hr /></p></p></blockquote><br />Fixed legs will burn off during atmospheric braking.<p><hr /></p></p></blockquote><br />Even with Mars' lower atmospheric pressure? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[JonClarke]

"Tanks for cryo-materials are heavy."<br /><br />Not as heavy as lithium-metal hydrides. Furthermopre there are no economies of scale. The mass to propellant ratio decreases with increasing amount of propellant as the pass of the tank increases according to the square where as the propellant mass increases by the cube.<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]

"I know that. However, the reason Boeing was able to push ETOPS through the FAA rule book was because the more engines a plane had, the more engines could fail. In fact, that was why Lindberg insisted on only one engine for the Spirit of St. Louis. With a lander, the more retractable legs you have, the more things you have to fail. "<br /><br />Let's look at the numbers. Say the probabiliy of a leg failing is 1/100. With four legs all four are needed. The probability of writing of the lander through leg failure is thus 0.9606, or 1/25. <br /><br />With five legs the probability of a single leg failure is 0.956. While this is higher (1/20 than the chance of failure with four legs, to wreck the lander you need two legs the fail. The The probability of that happening is 0.9999, or 1/10,000. <br /><br />Also note that Mars landers are heavy, somewhere between 30 and 60 tonnes on touchdown. The more legs the lower the ground pressure.<br /><br />"Even with Mars' lower atmospheric pressure?"<br /><br />Descending from Mars orbit to the surface requires a dV of ~5 km/s. About 4 km/s will be shed through atmsopheric breaking. If you legs are not folded away behind a heat shield, they will turn off.<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>

 

[holmec]

Get a refill at the surface!<br /><br />Shoot, if you use a parachute for some of the decent then less propellant is needed.<br /><br />I wonder if anyone thought of long legs that the craft can use to slow itself down from the time the legs touched the ground to the time the craft stop. The craft could then slow itself on the long legs with mechanical brakes. <br /><br />Or you could have a cental long pole that hits the ground and the craft can brake on it before it lands. That could serve as a cushioning effect.<br /><br />Or you could make it a really big air bag that is several times the height of the craft. As the air bag deflates, the craft could balance on it with thrusters. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[qso1]

JonClarke:<br />Remember that SSTO is much easier on Mars than on earth, orbital velocity is only 5 km/s.<br /><br />Me:<br />Correct, which means the design will be scaled to operate on mars and as such, will require propellant loads consistent with the vehicles size. The DC-X or Delta Clipper could probably almost go to orbit from mars and return to the surface. If a DC-Y were built for mars, then additional payload capacity would be present.<br /><br />JonClarke:<br />Surface yes, but why in orbit?<br /><br />Me:<br />If used repeatedly, the vehicle will be in orbit when it prepares to land. It will be at maximum propellant load for landing, and then subsequent return to orbit where a propellant depot would be required to allow repeated landing and orbital return cycles.<br /><br />JonClarke:<br />"But then, anything mars will involve more than what is generally anticipated or proposed in mars mission plans." <br /><br />Meaning?<br /><br />Me:<br />Just that anything we plan to do, we almost always run into some unanticipated bumps in the road. This really applies to just about any major planning. But where mars is concerned, when plans reach the public, they almost always show only the main gist of the plan. An example being a mars lander on the cover of a magazine with an astronaut outside. Unless the magazine goes into great detail, and the plan itself includes great detail, the public only gets a general idea of what to expect.<br /><br />We always here the tagline in books and movies..."Things didn't go according to plan". We hear it so much, its cliche. <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>

 

[qso1]

A parachute would be a good idea actually. And for the two stage lander I show in my book, parachutes are used. As for legs, the simpler the better. Unfortunately, I had to come up with a somewhat complex two type of leg design for my book concept. But thats beside the point.<br /><br />The chutes would have to come off prior to landing.<br /><br />holmec:<br />I wonder if anyone thought of long legs that the craft can use to slow itself down...<br /><br />Me:<br />Leg length is added mass which means using propellant to slow down is probably the more practical approach. Extremely long legs will create stability problems associated with the strength of the legs as well.<br /><br />holmec:<br />Or you could have a cental long pole that hits the ground and the craft can brake on it before it lands.<br /><br />Me:<br />This would have stability problems associated with keeping the craft from tilting on the pole. However, in the design I mentioned, I used 4 telescoping poles to assist in a propulsive braking and stabilization. It too is not the perfect solution because it involved more mass, but I'm not the worlds best designer. <br /><br />holmec:<br />Or you could make it a really big air bag that is several times the height of the craft. As the air bag deflates, the craft could balance on it with thrusters.<br /><br />Me:<br />A really big bag could interfere with the crews ability to get out of the craft, making EVA more difficult. OTOH, it could be quite useful as it would provide some materials that could be used for other pruposes once the main purpose has been fullfilled.<br /><br />Bottom line, a DC-X lander is possible on mars as is a two stage lander. The trade off is that more propellant is required for a DC-X type lander but this is not a showstopper, especially a DC-X type lander assigned to a base as a crew transport. And per your original parachute idea, a DC-X with a parachute landing assist capability will free up more payload capacity so long as the parachutes don't cut in <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>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p><blockquote><font class="small">In reply to:</font><hr /><p>Surface yes, but why in orbit?<p><hr /></p></p></blockquote>If used repeatedly, the vehicle will be in orbit when it prepares to land. It will be at maximum propellant load for landing, and then subsequent return to orbit where a propellant depot would be required to allow repeated landing and orbital return cycles.<p><hr /></p></p></blockquote><br />How would you get fuel to the orbital refueling point? Would you ship it from Earth? That would be a big waste. I think we are better off ensuring the lander can make round trips back to the surface and refuel there. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[JonClarke]

qso1 - An SSTO (DC-X derived) could then serve as the primary means of crew transport to and from the martian surface once a base has been established. This will still require a propellant infrastructure to service the DC-X derivative in martian orbit and on the surface"<br /><br />JC - Surface yes, but why in orbit?<br /><br />qso1 in response - If used repeatedly, the vehicle will be in orbit when it prepares to land. It will be at maximum propellant load for landing, and then subsequent return to orbit where a propellant depot would be required to allow repeated landing and orbital return cycles.<br /><br />The surface of Mars is where the propellant can be most easily manufactured. Abundant CO2 everywhere and H2O in some places.<br /><br />In terms of propellant requirements, using methane-LOX it takes a propellant mass about four times the dry mass to reach LMO. It takes about one quarter the dry mass to soft land. <br /><br />Assuming a SSTO dry mass of 20 tonnes, if you refuel on the surface your launch mass will be need 20 + 5 tonnes X 5 = 125 tonnes, of which 105 tonnes will be propellant. <br /><br />If you refuel in LMO, your landed mass will equal your return mass, which is 5 X 20 = 100 tonne tones. The propellant to land that comes to a quarter of this which is 25 tonnes. Total propellant mass required in the LMO refuelling scenario is 105 tonnes. <br /><br />While the propellant masses are the same, it doing to be much easier to land a 20 tonne vehcile than a 100 tonne one.<br /><br />qso1 - But then, anything mars will involve more than what is generally anticipated or proposed in mars mission plans."<br /><br />JC- Meaning?<br /><br />qso1 in response - Just that anything we plan to do, we almost always run into some unanticipated bumps in the road. This really applies to just about any major planning. But where mars is concerned, when plans reach the public, they almost always show only the main gist of the plan. An example being a mars lander on the cover of <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]

willpittenger:<br />How would you get fuel to the orbital refueling point? Would you ship it from Earth? That would be a big waste. I think we are better off ensuring the lander can make round trips back to the surface and refuel there. <br /><br />Me:<br />Agreed, but in the early phases of a mars base for example. Propellant may have to be shipped from earth until martian options prove viable. But then again, they may be able to set up propellant resupply on the surface using Zubrin proposed methane extraction methods. <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>

 

[qso1]

Propellant resupply on the surface of mars has to be proven but I don't see any real obstacle to it becoming operational. It all just depends on how we go about setting up human expeditions to mars and what will prove cost effective in the long run.<br /><br />And yes, the person who sees a lander on the cover of a mag and assumes its that easy will be in for a shock. Unfortunately, thats how the lay public often is. But it goes deeper than that.<br /><br />Maintenance of a DC-X like SSTO if one were operating on mars today, would be a headache if for example, we went with the block II SSME powered SSTO proposal that was to have emerged from the DC-X tests.<br /><br />Imagine regular maintenance on an SSME in an EMU. Those hard to get to places become nearly impossible to reach and maintenance takes longer than planned.<br /><br />Ultimately however, those are just things we in the space community already know of and its just a matter of getting around them as best we can and fortunately, by the time we get a mars base going...we should be able to do an SSTO with a more robust main propulsion system. <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>

 

[willpittenger]

I was having troubles following who replied to who in your post. Could you clean it up a little? It would help. Thanks. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>