Rocketman Type MMU, For Lunar Exploration

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kyle_baron

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<p>When NASA goes back to the moon in 2020, they'll explore the south pole region for a lunar base.&nbsp; Water (ice) is supposed to exist in the craters there.&nbsp; I went to the NASA web site, and they say some of these craters are 2.5-3 miles deep.&nbsp; To get in and out of these craters, astronauts will need a propulsion unit:</p><p>&nbsp;</p><p>http://en.wikipedia.org/wiki/Manned_Maneuvering_Unit</p><p>&nbsp;</p><p>Is it possible to upgrade an existing 20 yr. old MMU, for lunar exploratory purposes on the moon?&nbsp; Or, will it have to be completely redesigned?&nbsp; Or, is it even feasible? </p><p>&nbsp;</p><p>From what I've read, a fully suited astronaut, with a fully loaded MMU weighs about 600 lbs.&nbsp; On the moon, that would be 100 lbs.&nbsp; The current MMU creates only 1 lb. of thrust from pressurized nitrogen.&nbsp; I'm thinking of strapping LH2 and LOX to the back of an MMU and turning the astronaut into a real, lunar, rocket man.&nbsp; Would this propellent give the necessary 100 lbs. of thrust to propell an astronaut the necessary 2-3 miles high, out of a crater?&nbsp; How long would an astronaut be able to maintain this thrust, if the tanks can hold 40 lbs. of propellent?&nbsp; Just looking for rough estimates.&nbsp; Here's two more links on the MMU:</p><p>&nbsp;</p><p>http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790008382_1979008382.pdf</p><p>&nbsp;</p><p>http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900001658_1990001658.pdf</p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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aphh

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It's obvious they'll need a service platform with thrust capabilities. But instead of wearing one, I'm thinking more like&nbsp; Armadillo type flying platform.
 
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Cygnus_2112

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>When NASA goes back to the moon in 2020, they'll explore the south pole region for a lunar base.&nbsp; Water (ice) is supposed to exist in the craters there.&nbsp; I went to the NASA web site, and they say some of these craters are 2.5-3 miles deep.&nbsp; To get in and out of these craters, astronauts will need a propulsion unit:&nbsp;http://en.wikipedia.org/wiki/Manned_Maneuvering_UnitIs it possible to upgrade an existing 20 yr. old MMU, for lunar exploratory purposes on the moon?&nbsp; Or, will it have to be completely redesigned?&nbsp; Or, is it even feasible? &nbsp;From what I've read, a fully suited astronaut, with a fully loaded MMU weighs about 600 lbs.&nbsp; On the moon, that would be 100 lbs.&nbsp; The current MMU creates only 1 lb. of thrust from pressurized nitrogen.&nbsp; I'm thinking of strapping LH2 and LOX to the back of an MMU and turning the astronaut into a real, lunar, rocket man.&nbsp; Would this propellent give the necessary 100 lbs. of thrust to propell an astronaut the necessary 2-3 miles high, out of a crater?&nbsp; How long would an astronaut be able to maintain this thrust, if the tanks can hold 40 lbs. of propellent?&nbsp; Just looking for rough estimates.&nbsp; Here's two more links on the MMU:&nbsp;http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790008382_1979008382.pdfhttp://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900001658_1990001658.pdf <br /> Posted by kyle_baron</DIV></p><p>&nbsp;</p><p>Not viable.&nbsp; The propellant load would be too small. &nbsp; the Bell Jetpack only could carry enough fuel for&nbsp; 1 minute of&nbsp; flight.&nbsp; Also legs are not reliable landing gear.&nbsp; This was looked at in the 60's and it was determined that a small vehicle would be needed </p>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Not viable.&nbsp; The propellant load would be too small. &nbsp; the Bell Jetpack only could carry enough fuel for&nbsp; 1 minute of&nbsp; flight.&nbsp; Also legs are not reliable landing gear.&nbsp; This was looked at in the 60's and it was determined that a small vehicle would be needed <br />Posted by Cygnus_2112</DIV></p><p>&nbsp;</p><p>Oh, I don't know about that:</p><p>&nbsp;</p><p>http://en.wikipedia.org/wiki/Bell_Rocket_Belt</p><p>&nbsp;</p><p>For the pack they selected a rocket engine with a thrust of 280 pounds-force (1.25 kN or 127 kgf). The pack with its fuel weighed 125 lb (57 kg).</p><p>&nbsp;</p><p>High thrust and low weight, makes this an interesting alternative.&nbsp; Compared to the MMU which had 1 lb. thrust (for an astronaut in orbit, or free fall).&nbsp; And IIRC, the MMU weighed in at 325 lbs.<br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Oh, I don't know about that:&nbsp;http://en.wikipedia.org/wiki/Bell_Rocket_BeltFor the pack they selected a rocket engine with a thrust of 280 pounds-force (1.25 kN or 127 kgf). The pack with its fuel weighed 125 lb (57 kg).&nbsp;High thrust and low weight, makes this an interesting alternative.&nbsp; Compared to the MMU which had 1 lb. thrust (for an astronaut in orbit, or free fall).&nbsp; And IIRC, the MMU weighed in at 325 lbs. <br />Posted by kyle_baron</DIV></p><p>&nbsp;</p><p>Probably not practical.&nbsp; However, here's another thought:&nbsp; What about 2 solid rocket engines (similar to the shuttle).&nbsp; One solid rocket to get into the crater, and one to get out.&nbsp; I thought I read somewhere, that solid rocket motors were throttle-able.&nbsp; These mini-SRB's could be refilled, once returned to Earth.&nbsp;</p><p>&nbsp;</p><p>&nbsp;http://en.wikipedia.org/wiki/Solid_rocket</p><p>&nbsp;</p><p>More advanced solid rocket motors can not only be throttled but can be extinguished and then re-ignited by controlling the nozzle geometry or through the use of vent ports. Also, pulsed rocket motors which burn in segments and which can be ignited upon command are available.</p><p>&nbsp;</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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Cygnus_2112

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Probably not practical.&nbsp; However, here's another thought:&nbsp; What about 2 solid rocket engines (similar to the shuttle).&nbsp; One solid rocket to get into the crater, and one to get out.&nbsp; I thought I read somewhere, that solid rocket motors were throttle-able.&nbsp; These mini-SRB's could be refilled, once returned to Earth.&nbsp;&nbsp;&nbsp;http://en.wikipedia.org/wiki/Solid_rocketMore advanced solid rocket motors can not only be throttled but can be extinguished and then re-ignited by controlling the nozzle geometry or through the use of vent ports. Also, pulsed rocket motors which burn in segments and which can be ignited upon command are available.&nbsp;&nbsp; <br /> Posted by kyle_baron</DIV></p><p>&nbsp;</p><p>Even less viable. They would weigh more than a liquid system.&nbsp; </p><p>MMU based design is out, it needs a structure with landing gear </p>
 
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Boris_Badenov

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<p><font size="2">As your mission requirements go up, so does the size of the fuel tank you need to accomplish the mission.</font></p><p><font size="2">Among their other excellent ideas SpaceDev has envisioned a rather unique method&nbsp;of landing on the Lunar surface & returning to orbit.</font></p><p><font size="2">http://www.youtube.com/watch?v=in8hPNhfTOo</font></p> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Even less viable. They would weigh more than a liquid system.&nbsp;</DIV></p><p>&nbsp;</p><p>So what.&nbsp; You would also get a lot more thrust.</p><p>&nbsp;</p><p>&nbsp;Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>MMU based design is out, it needs a structure with landing gear <br />Posted by Cygnus_2112</DIV></p><p>&nbsp;</p><p>I'll agree.&nbsp; That's why I like Boris 1961's idea of a rocket chair.&nbsp; Maybe with McPherson struts on each leg!<br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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Cygnus_2112

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;So what.&nbsp; You would also get a lot more thrust<br /> Posted by kyle_baron</DIV></p><p>Incorrect. Just&nbsp; because it is a solid, doesn't mean it has more thrust.&nbsp; Solids, just like liquid engines can sized for the task at hand.&nbsp;&nbsp; With a solid motor, it has a lower ISP, which means more propellant mass is needed. &nbsp; </p>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Incorrect. Just&nbsp; because it is a solid, doesn't mean it has more thrust.&nbsp; Solids, just like liquid engines can sized for the task at hand.&nbsp;&nbsp; With a solid motor, it has a lower ISP, which means more propellant mass is needed. &nbsp; <br />Posted by Cygnus_2112</DIV></p><p>&nbsp;</p><p>Now that we've removed the human legs, and substituted them for 4&nbsp;LEM legs (with McPherson struts) the sky is the limit.&nbsp; Having longer LEM legs enables larger and longer propellent tanks.&nbsp; Yes, you are correct, solid rocket motors aren't as efficient, but either method, IMO could now be used.</p><p>&nbsp;</p><p>http://en.wikipedia.org/wiki/Specific_impulse</p><p>&nbsp;</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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KosmicHero

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Now that we've removed the human legs, and substituted them for 4&nbsp;LEM legs (with McPherson struts) the sky is the limit.&nbsp; Having longer LEM legs enables larger and longer propellent tanks.&nbsp; Yes, you are correct, solid rocket motors aren't as efficient, but either method, IMO could now be used.&nbsp;http://en.wikipedia.org/wiki/Specific_impulse <br />Posted by kyle_baron</DIV><br /><br />Please provide a link to these throttleable solids.&nbsp; </p><p>My recommendation is to use storable liquids.&nbsp; They're easier to restart, don't need a lot of special equipment to keep, and they're safer.&nbsp; You'll have to take a small penalty in performance compared to the high-energy O2/H2, but I think the reliability and risk-reduction is a good trade.&nbsp; </p><p>&nbsp;There are several designs on Lunar Hoppers but they are mainly used for longer distance 'hops' (on the order of 100&nbsp; km).&nbsp; I think this is a good idea.&nbsp; Some NewSpace startup or enthusiast group should take this up as a design project.</p> <div class="Discussion_UserSignature"> kosmichero.wordpress.com </div>
 
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Boris_Badenov

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<p><font size="2">The fuel storage tanks on the Apollo LEM weren't very big. The specs are in this article.</font></p><p><font size="2">http://www.astronautix.com/craft/lmdlsion.htm</font></p><p><font size="2">IIRC they were Hypergolics also.</font></p> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>
 
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Swampcat

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I think this is a good idea.&nbsp; Some NewSpace startup or enthusiast group should take this up as a design project. <br />Posted by KosmicHero</DIV><br /><br />Armadillo Aerospace is already on it.</p><p>http://media.armadilloaerospace.com/2002_09_28/firstMannedFlight.mpg</p><p><br /><img src="http://sitelife.space.com/ver1.0/Content/images/store/11/11/9b226901-38e7-4b1d-bbe9-4d536031be90.Medium.jpg" alt="" /></p> <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Armadillo Aerospace is already on it.http://media.armadilloaerospace.com/2002_09_28/firstMannedFlight.mpg <br />Posted by Swampcat</DIV></p><p>&nbsp;</p><p>Thanks!&nbsp; Cool video, for a 4 sec. flight.&nbsp; Looks like he had a hard landing.&nbsp; McPherson struts are the solution.</p><p>&nbsp;</p><p>In the video, the pilot is close to the ground.&nbsp; I envision something much taller (like a Mini-LEM).&nbsp; Maybe 8 feet high.&nbsp; Where the pilot would have to climb a ladder, or a step,&nbsp;to get to the seat.&nbsp;&nbsp;This Mini-LEM&nbsp;could fold up, like the lunar rover did, on the side of the LEM.</p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Armadillo Aerospace is already on it.http://media.armadilloaerospace.com/2002_09_28/firstMannedFlight.mpg <br />Posted by Swampcat</DIV></p><p>&nbsp;</p><p>The nitrous oxide thrusters in the video would make good maneuvering thrusters for an RCS system, but not as the main power source.&nbsp; The nitrous oxide might be used to decend the vehicle into a crater, but not powerful enough to get out of one, IMO.<br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The fuel storage tanks on the Apollo LEM weren't very big. The specs are in this article.http://www.astronautix.com/craft/lmdlsion.htmIIRC they were Hypergolics also. <br />Posted by boris1961</DIV></p><p>&nbsp;</p><p>I found some excellent spec's on the LEM here:</p><p>&nbsp;</p><p>http://www.braeunig.us/space/specs/lm.htm</p><p>&nbsp;</p><p>For the descent stage, I have a question.&nbsp; Since the specific impulse is 311 sec. (5 min.), by throttling the engine down to 55%, does that allow the extended burn time to increase to 12.5 min ?&nbsp; Also, the delta v is 2,470 m/s.&nbsp; Is that a little over 1 mi. per sec. at full throttle?<br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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qso1

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<p>The main problem with a rocket belt MMU approach will be safety. Can and would lunar astronauts operate the system safely enough?</p> <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>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The main problem with a rocket belt MMU approach will be safety.</DIV></p><p>&nbsp;</p><p>By consensus, we've gone to a rocket chair type of MMU, eliminating the astronauts legs, which is the weakest link.&nbsp;</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Can and would lunar astronauts operate the system safely enough? <br />Posted by qso1</DIV></p><p>&nbsp;</p><p>If NASA wants to explore the south pole region, riding around in the lunar rover, won't get the astronauts in the craters, where the ice&nbsp;should be.&nbsp; IMO, the safety risk is acceptable, as long as, a large and powerful enough rocket motor is used.&nbsp; It should be throttleable, with enough propellent to get in and out of 2 or more craters.&nbsp;</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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qso1

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<p>You or I might be of the opinion that its safe enough, but were talking NASA here and some of the hoops they have to jump through to get political support. Especially in the risk averse climate of today.&nbsp;</p> <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>
 
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aphh

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> does that allow the extended burn time to increase to 12.5 min ?&nbsp; Also, the delta v is 2,470 m/s.&nbsp; Is that a little over 1 mi. per sec. at full throttle? <br /> Posted by kyle_baron</DIV></p><p>So roughly 1/3G on average was experienced by the astronauts during descent to the surface. 2470/750 = 3.29 m/s? That is a smooth ride to the surface of the moon.&nbsp;</p>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You or I might be of the opinion that its safe enough, but were talking NASA here and some of the hoops they have to jump through to get political support. Especially in the risk averse climate of today.&nbsp; <br />Posted by qso1</DIV></p><p>&nbsp;</p><p>What NASA really needs, is more interest from the general public, in exploring the moon.&nbsp; The Lunar Rover isn't that exciting anymore.&nbsp; I think, by using a rocket chair, astronauts can explore craters, and lava tunnels beneath the surface.&nbsp; And explore the tops of hills, and mountains, above the surface of the moon.&nbsp; The only other thing needed, is a tv camera mounted to the rocket chair, so the general public can go along for the ride!&nbsp; <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" /><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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aphh

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Yup. What we want is the people to look up in the sky and see the moon and think: "my god, there's people there living and working right now".
 
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qso1

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<p><font color="#800080">What NASA really needs, is more interest from the general public, in exploring the moon.&nbsp; The Lunar Rover isn't that exciting anymore.&nbsp; I think, by using a rocket chair, astronauts can explore craters, and lava tunnels beneath the surface.&nbsp; And explore the tops of hills, and mountains, above the surface of the moon.&nbsp; The only other thing needed, is a tv camera mounted to the rocket chair, so the general public can go along for the ride!&nbsp; <br /> Posted by kyle_baron</font></p><p>Not a bad idea. I can imagine some of the shots that would be obtained in this way. Even movie or documentary producers would probably want to use that footage.&nbsp;</p> <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>
 
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qso1

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<p><font color="#800080">Yup. What we want is the people to look up in the sky and see the moon and think: "my god, there's people there living and working right now". Posted by aphh</font></p><p>Especially folks who might be thinking of going and working on the moon.&nbsp;</p> <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>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Probably not practical.&nbsp; However, here's another thought:&nbsp; What about 2 solid rocket engines (similar to the shuttle).&nbsp; One solid rocket to get into the crater, and one to get out.&nbsp; I thought I read somewhere, that solid rocket motors were throttle-able.&nbsp; These mini-SRB's could be refilled, once returned to Earth.&nbsp;&nbsp;&nbsp;http://en.wikipedia.org/wiki/Solid_rocketMore advanced solid rocket motors can not only be throttled but can be extinguished and then re-ignited by controlling the nozzle geometry or through the use of vent ports. Also, pulsed rocket motors which burn in segments and which can be ignited upon command are available.&nbsp;&nbsp; <br />Posted by kyle_baron</DIV></p><p>The only practical throttlelable solids of which I am aware are air breathers, though pintle nozzles have been studied.&nbsp; I am not aware of any notions for extinguishment by varying nozzle geometry.&nbsp; Extinguishing a solid rocket can be done via very rapid depressurization, generally too rapid to be performed by simply varying nozzle geometry.&nbsp; It is usually done explosively with no intent to re-ignite.&nbsp; The vent port idea is more commonly used for thrust reversal, usually for staging purposes, and more commonly in older designs.&nbsp; Ignition of a solid is accomplished with a separate component, called an igniter, wihich is a one-time use item.&nbsp; Multiple ignitions require multiple ignition systems.&nbsp; This can be done, but it takes some serious engineering.</p><p>Pulsed rockets are fairly common among tactical rockets.&nbsp; There are no large (as in space launch size) pulse solids in production, and I don't know of any that have ever been tested.&nbsp; Two pulse motors have been produced.&nbsp; SRAM II was one.&nbsp; There are others.&nbsp; Design of the mechanisms to keep the second grain from igniting while the first one burns takes some work.&nbsp; So does design of ignition systems.</p><p>Refilling SRBs is of dubious economics.&nbsp; I know that it is done on the&nbsp;shuttle, and I am quite familiar with the process for refurbishing them.&nbsp; I believe that the economics is a bit iffy even there and for small motors and quite sure that the economics won't support re-use.&nbsp; The cleaning, refurbishing and inspection of used parts would cost more than using new ones.&nbsp; For something like the personal propulsion system that&nbsp; you are talking about a cartridge-loaded system like that use for the Hydra-70 missile (the one you see launched out of a pod on helicopters) would probably be the way to go.</p><p>But, with solids you don't get easy throttleability and without that you certainly would not be able to convince me to strap one of these things on.</p><p>With any rocket you also get&nbsp;hot gasses and the possibility of an occasional explosion.&nbsp; I think I would stay away from those.&nbsp;</p><p>There have been hybrids tested.&nbsp; Solid fuel grains with liquid oxidizers.&nbsp; Those are throttleable.&nbsp; But they have their own set of problems.</p><p>Personally I agree with the assessment that a vehicle is the way to go.&nbsp; With that you get relatively easy controllability, and the ability to carry a practical cargo load.&nbsp; <br /></p> <div class="Discussion_UserSignature"> </div>
 
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