eder@ssc-vax.UUCP (Dani Eder) (02/05/86)
> There have recently been several postings relating to > electromagnetic launch from the Earth's surface. > Why not use an accelerator boost for a next-generation shuttle? > For an example, let's suppose this is Mount Kenya, a 5 Km > tall mountain on the equator (the most efficient place to launch > from, at least if you want equatorial orbits.) > > --Geoffrey A. Landis > Brown U. [extensive calculations deleted from above article] The basic idea of electromagnetic accelerators to launch things off the Earth is quite sound. I have a few comments to make on your idea. In general, your launch facility will be expensive and you would want to minimize it's cost and maximize the number of payloads you pump through it so as to spread the cost around. This tends to drive you to as small a launcher as possible and as small a payload size as possible, with a high launch rate. At least for the first launcher you build. If your electrical efficiency is high, you will want to do as much of the acceleration as possible electrically, and minimize the chemical rocket part. A limiting factor is atmospheric heating as you leave the gun at high Mach numbers. A last point I would like to make is you do not have to limit yourself to mountains. With modern structural materials one can build towers that literally extend out of the atmosphere. As an example, T300/934 Graphite/Epoxy composite, which is used in airplanes, has a density of 0.057lb/in^3 and a compressive strength of 215800 lb/in^2. If we divide strength by density we get the height of a column of graphite/epoxy that just barely can support it's own weight. It is 3.786 million inches or 59.7 miles. If we taper the tower, we can make it taller. You also want to work at less than theoretical strength, but the order of magnitude is correct. The cost driver on electromagnetic launchers seems to be the power supplies. You need a Gigawatt pulse on the order of seconds long. Fortunately the magnetic fusion folks are already developing such power suppllies for their own experiments. Thus, at present all the key technologies are in hand or under intensive development. It remains for some far sighted individuals to do a convincing demonstration for the world. It would give people the idea that rockets are not the only way to get into space. Reaching for the stars!/Dani Eder/Boeing/Advanced Space Transportation ssc-vax!eder
mikes@apple.UUCP (Mike Shannon) (02/07/86)
>as you leave the gun at high Mach numbers. A last point I would like to >make is you do not have to limit yourself to mountains. With modern >structural materials one can build towers that literally extend out of >the atmosphere. As an example, T300/934 Graphite/Epoxy composite, which >... This is GREAT! Let's just build an elevator to outer space! Just climb in, punch the button for floor 39,254 , and jump off! (We should note that this was tried once before, in biblical times. :-) (I wonder how many stories tall you'd have to go to get to geostationary orbit? That would be some elevator panel! :=) -- Michael Shannon {apple!mikes}
holloway@drivax.UUCP (Bruce Holloway) (02/11/86)
> (I wonder how many stories tall you'd have to go to get to geostationary >orbit? That would be some elevator panel! :=) >-- > Michael Shannon {apple!mikes} You'd want to get off somewhere near floor 7,744,000. Build this elevator, and five'll get you ten that some nut will run a marathon up the fire stairs.
mangoe@umcp-cs.UUCP (Charley Wingate) (02/12/86)
In article <15500@apple.UUCP> mikes@apple.UUCP writes: >> A last point I would like to >>make is you do not have to limit yourself to mountains. With modern >>structural materials one can build towers that literally extend out of >>the atmosphere. > This is GREAT! Let's just build an elevator to outer space! Just >climb in, punch the button for floor 39,254 , and jump off! (We should note >that this was tried once before, in biblical times. :-) > (I wonder how many stories tall you'd have to go to get to >geostationary orbit? That would be some elevator panel! :=) Too late. As with many other space developments, Arthur C. Clarke has already explored the idea-- in this case, in the novel _The Fountains of Paradise_. It also contains lots of local color (from Sri Lanka, where else?). Suffers from all the late Clarke flaws, but an interesting technical piece nonetheless. C. Wingate
ins_akaa@jhunix.UUCP (Ken Arromdee) (02/12/86)
In article <15500@apple.UUCP> mikes@apple.UUCP writes: > This is GREAT! Let's just build an elevator to outer space! Just >climb in, punch the button for floor 39,254 , and jump off! (We should note >that this was tried once before, in biblical times. :-) > (I wonder how many stories tall you'd have to go to get to geostationary >orbit? That would be some elevator panel! :=) > Michael Shannon {apple!mikes} Believe it or not, building an elevator to outer space is a perfectly plausible idea, though modern materials seem to be somewhat lacking in tensile strength. There was an Arthur C. Clarke novel, The Fountains of Paradise, based on exactly that idea. And it does go to geostationary orbit, with some mass farther out as a balance. -- "We are going to give a little something, a few little years more, to socialism, because socialism is defunct. It dies all by iself. The bad thing is that socialism, being a victim of its... Did I say socialism?" -Fidel Castro Kenneth Arromdee BITNET: G46I4701 at JHUVM and INS_AKAA at JHUVMS CSNET: ins_akaa@jhunix.CSNET ARPA: ins_akaa%jhunix@hopkins.ARPA UUCP: ...allegra!hopkins!jhunix!ins_akaa