Long cables to power plasma rockets to orbit.

Page 3 - Seeking answers about space? Join the Space community: the premier source of space exploration, innovation, and astronomy news, chronicling (and celebrating) humanity's ongoing expansion across the final frontier.
Status
Not open for further replies.
E

exoscientist

Guest
While doing a web search I found a report on creating inflatable vacuum chambers, where the walls are filled with pressurized gas for strength. Such chambers could even be buoyant if the walls were filled with a lighter than air gas such as helium.<br />This then could be used to extend a vacuum travel path from the ground all the way to high altitude for orbital rocket launch.<br /><br />Stability Analysis of an Inflatable Vacuum Chamber.<br />http://arxiv.org/abs/physics/0610222v4 <br /><br /><br /> Bob Clark <div class="Discussion_UserSignature"> </div>
 
N

neilsox

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That's an interesting point. Altitude is not what gets you in orbit, horizontal velocity is. So a space elevator gets very squirrely as a mass gains altitude but not horizontal velocity. I haven't seen that issue addressed in any Space Elevator threads AFAIR. Hmmmm. <br />Posted by MeteorWayne</DIV></p><p>You do gain a little horizontal velosity as you climb the space elevator. richalex is almost correct. The space elevator is optimum for GEO orbit and beyond, but you can get to low Earth orbit by droping off the space elevator about 3/4 of the way to GEO altitude. You drop like a rock, missing Earth by a few hundred kilometers, in a highly eliptical orbit. You need some energy to circulize the orbit, but it is much less than the energy to lift from Earth's surface.</p><p>While some forms of CNT conduct electricity almost as well as copper or aluminum, CNT is not a superconductor except near absolute zero, so I agree the long extenion cord magnetoplasmadynamic engine is practical for only the first 3 or 4 kilometers, unless&nbsp;enough electricity can be delivered by laser beam, which is also low probability.&nbsp; &nbsp;Neil</p>
 
C

Cygnus_X_1

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Magnetoplasmadynamic thrusters have the advantage that they can be scaled up to produce large amounts of thrust, while still maintaining the high ISP of ion drives: Magnetoplasmadynamic Thrusters. "Testing for these thrusters has demonstrated exhaust velocities of 100,000 meters per second (over 200,000 mph) and thrust levels of 100 Newtons (22.5 pounds) at power levels of 1 megawatt. For perspective, this exhaust velocity will allow a spacecraft to travel roughly 11 times the top speed of the space shuttle (18,000 mph)." http://www.nasa.gov/centers/glenn/about/fs22grc.html MY ELECTRIC ROCKET ENGINE. http://www.waynesthisandthat.com/mpd.htm The problem is the high amount of power required. However high electrical power has been delivered up to hundreds of kilometers on Earth over power lines. Then this could be used to deliver the required electrical power to the thrusters from the ground. Bob Clark c.f., Newsgroups: sci.astro, sci.space.policy, sci.physics From: "Robert Clark" <rgregorycl...@yahoo.com /> Date: 20 Mar 2006 20:23:18 -0800 Local: Mon, Mar 20 2006 11:23 pm Subject: Long cables to power arcjet rockets to orbit? http://groups.google.com/group/sci.physics/msg/0cd3fba4a33a6d13 <br /> Posted by exoscientist</DIV></p><p>&nbsp;</p><p>This idea was debunked on USEnet and NASASpaceflight.com.&nbsp; Are the laws of physics different on SDC where this fool's folly will work?</p> <div class="Discussion_UserSignature"> </div>
 
M

MeteorWayne

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You do gain a little horizontal velosity as you climb the space elevator. richalex is almost correct. The space elevator is optimum for GEO orbit and beyond, but you can get to low Earth orbit by droping off the space elevator about 3/4 of the way to GEO altitude. You drop like a rock, missing Earth by a few hundred kilometers, in a highly eliptical orbit. You need some energy to circulize the orbit, but it is much less than the energy to lift from Earth's surface.While some forms of CNT conduct electricity almost as well as copper or aluminum, CNT is not a superconductor except near absolute zero, so I agree the long extenion cord magnetoplasmadynamic engine is practical for only the first 3 or 4 kilometers, unless&nbsp;enough electricity can be delivered by laser beam, which is also low probability.&nbsp; &nbsp;Neil <br />Posted by neilsox</DIV></p><p>Yes you do, but all of that horizontal velocity comes from force along the cable. Otherwise, especially low on the wire, any h v&nbsp; would be lost from friction with the atmosphere.</p><p>You definately have to carefully manage the load!</p><p>Also, even neglecting the atmosphere, an orbit regures that your speed be ~ 17,500 mph. Your speed on the surface is ~ 1000 mph. So the satellite (mass) has to be accelerated horizontally from 1000 to 17,500 mph.</p><p>The only force to do that is from the elevator cable. It's trying to accelerate a mass horizontally at the most inefficient angle possible, 0 degrees to start. So in the beginning, the force required is infinity, not good. So presumably the ascent would take place at some angle downstream to reduce the stress at the start. Still, the angle is poor to transmit the required orbital velocity.</p><p>I haven;t seen this issue addressed specifically. If anyone sees a flaw in my logic, help me understand.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
J

jouler

Guest
<p>So how far could we get with what we have?&nbsp; You choose the amperage so power throughput becomes the first limitation.&nbsp; At 1 MV, an arc will jump 16', so you couldn't build an orbital vehicle much bigger diameter than that.&nbsp; Standard aluminum/steel EHV transmission conductor is rated at 1,000 MW continuous.&nbsp; It is 3 cm in diameter and weighs 1.4 lbs/ft.&nbsp; 1MW can lift 22.5 lbs, so&nbsp;1,000 MW could lift 22,500 lbs, or just under 5 km, less the weight of the engine and payload (10 km with ballons, etc).&nbsp; This weight also approaches the breaking strength of the cable, now fully supported by the rocket.&nbsp; The final limitation is the&nbsp;speed of sound in Aluminum,&nbsp;less than orbital velocity @ 4.8 km/s vs 7km/s.&nbsp; Exotic materials could bump performance some, but not enough</p><p>http://www.engineeringtoolbox.com/sound-speed-solids-d_713.html</p><p>http://en.wikipedia.org/wiki/Orbital_speed</p> <div class="Discussion_UserSignature"> </div>
 
E

exoscientist

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>So how far could we get with what we have?&nbsp; You choose the amperage so power throughput becomes the first limitation.&nbsp; At 1 MV, an arc will jump 16', so you couldn't build an orbital vehicle much bigger diameter than that.&nbsp; Standard aluminum/steel EHV transmission conductor is rated at 1,000 MW continuous.&nbsp; It is 3 cm in diameter and weighs 1.4 lbs/ft.&nbsp; 1MW can lift 22.5 lbs, so&nbsp;1,000 MW could lift 22,500 lbs, or just under 5 km, less the weight of the engine and payload (10 km with ballons, etc).&nbsp; This weight also approaches the breaking strength of the cable, now fully supported by the rocket.&nbsp; The final limitation is the&nbsp;speed of sound in Aluminum,&nbsp;less than orbital velocity @ 4.8 km/s vs 7km/s.&nbsp; Exotic materials could bump performance some, but not enoughhttp://www.engineeringtoolbox.com/sound-speed-solids-d_713.htmlhttp://en.wikipedia.org/wiki/Orbital_speed <br />Posted by jouler</DIV><br /><br />&nbsp;I don't see why the size of the vehicle has to be limited by the voltage. </p><p>&nbsp;Also, the great length of the cable, the part that remains static in place,&nbsp;could be made buoyant itself if filled with lighter than air gas so that it would support its own weight. In that case it could be arbitrarily long. There would have to be though means for keeping it stable against winds, perhaps by&nbsp;thrusters or even propellers along its length.</p><p>&nbsp;However, there is another problem raised on another forum on this idea. Rockets to orbit are not made to stay close to a fixed trajectory, as would be required here to transmit the power&nbsp;from the long transmission cable to the rocket. Rockets are only designed to maintain a particular attitude to minimize the aerodynamic loads on the vehicle at the high Mach velocities. So it could wind up several kilometers from the planned ideal trajectory by the time it reaches orbit. It might be possible to have thrusters along the sides of the vehicle to make adjustments to its position, so that it would remain close to its planned trajectory during the entire trip. If the thrusters are at several points along its length and made to fire in unison so that the vehicle is made to move uniformly in the desired direction to correct for drift, it might be possible to reduce the structural loads placed on the vehicle.</p><p>&nbsp; Bob Clark&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
C

Cygnus_X_1

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> However, there is another problem raised on another forum on this idea. Rockets to orbit are not made to stay close to a fixed trajectory, as would be required here to transmit the power&nbsp;from the long transmission cable to the rocket. Rockets are only designed to maintain a particular attitude to minimize the aerodynamic loads on the vehicle at the high Mach velocities. So it could wind up several kilometers from the planned ideal trajectory by the time it reaches orbit. It might be possible to have thrusters along the sides of the vehicle to make adjustments to its position, so that it would remain close to its planned trajectory during the entire trip. If the thrusters are at several points along its length and made to fire in unison so that the vehicle is made to move uniformly in the desired direction to correct for drift, it might be possible to reduce the structural loads placed on the vehicle.&nbsp; Bob Clark&nbsp;&nbsp; <br /> Posted by exoscientist</DIV></p><p>&nbsp;Not possible.&nbsp; The thrusters would not work and are not needed anyways..&nbsp; The LV can already manuever themselves.&nbsp; </p><p>The attitude LV's fly at is related to the winds at that particular altitude.&nbsp; This is to reduce the stress on the vehicle.&nbsp; Thrusters would do the opposite and induce more stress by "forcing" the vehicle into a certain path</p><p>&nbsp;</p><p>Just drop this idea, it is not viable and won't work.&nbsp;&nbsp; It is not backup by any relevant physics, just a bunch of unrelated topics.&nbsp; Because you don't have physics or engineering knowledge, you can't see why it won't work. </p> <div class="Discussion_UserSignature"> </div>
 
J

jimglenn

Guest
<p>I thought this was an April 1st type thread. Any of the suggested ideas alone are impractical. The best ion engines are too weak by many orders of magnitude. Even a single trailing wire (used in the one space experiment, needles allowed the electrons to complete the circuit) is impossible to physically implement, regardless of whether or not it could carry the power.</p><p>Imagine the wire feed mechanism as you approach Mach 18 or so. How could that even work at Mach 1? You would have to shoot the wire out of a gun. The aerodynamic drag of this wire whipping all around will slow the rocket. THE WIRE WILL BREAK.</p><p>Stick with LOX and hydrogen. Most ISP of anything. That's why spaceflight is so expensive. &nbsp;</p><p>&nbsp;</p><p>&nbsp;</p><p>&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
E

exoscientist

Guest
<p>&nbsp;You have to look at the beginning of the thread. The many kilometer long power transmission line is not supported by the rocket. It is kept fixed in place at high altitude either by light-than-air buoyancy methods or by its own thrusters/propellers. There are of course electrical power lines that travel hundreds of kilometers now that carry up to a 1 gigawatts of power. The idea would be to have something similar except supported at high altitudes. The rocket would travel in a trajectory close to this power line, say within a few hundreds of meters or within a few kilometers, with the power transmitted to a short conducting tether carried by the rocket.</p><p>&nbsp;At the beginning of the thread it was mentioned there are plasma engines that can produce high thrust at high Isp.</p><p>&nbsp;</p><p>&nbsp;&nbsp;&nbsp; Bob Clark<br />&nbsp; </p> <div class="Discussion_UserSignature"> </div>
 
J

jimglenn

Guest
<p>So you will build a vertical high tension line in the sky, held up and carrying millions of watts of power. That alone is too hard. It will still be too heavy to go even a mile high. Balloons will get blown all over the place. The cable will be writhing like a snake, and things will break. Then you have to get the power thru a "tether" to the rocket. Again, it is too hard. Contact, galvanic methods, like slip rings will not work, too much friction. Inductive methods will not handle that amount of power (or would slip rings). The tether would be horizontal with a lot of drag, how can it accelerate with the rocket to Mach 18?</p><p>Look at a lightweight nuclear reactor. That is far out, but can work. Power whatever you want with it. One buddy from black ops of mil aerospace says they have a propulsion system consisting of a very powerful laser pumping a toroidal magnetic chamber, the power just runs away to incredible levels. A light ring will generate a magnetic field, mass attributes, and possible gravitational effects. Oh yeah.....</p><p>&nbsp;</p><p>&nbsp;</p><p>&nbsp;</p><p>He said it is a UFO drive.</p><p><img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-surprised.gif" border="0" alt="Surprised" title="Surprised" /> </p> <div class="Discussion_UserSignature"> </div>
 
C

Cygnus_2112

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;I don't see why the size of the vehicle has to be limited by the voltage. &nbsp;Also, the great length of the cable, the part that remains static in place,&nbsp;could be made buoyant itself if filled with lighter than air gas so that it would support its own weight. In that case it could be arbitrarily long. There would have to be though means for keeping it stable against winds, perhaps by&nbsp;thrusters or even propellers along its length.&nbsp;However, there is another problem raised on another forum on this idea. Rockets to orbit are not made to stay close to a fixed trajectory, as would be required here to transmit the power&nbsp;from the long transmission cable to the rocket. Rockets are only designed to maintain a particular attitude to minimize the aerodynamic loads on the vehicle at the high Mach velocities. So it could wind up several kilometers from the planned ideal trajectory by the time it reaches orbit. It might be possible to have thrusters along the sides of the vehicle to make adjustments to its position, so that it would remain close to its planned trajectory during the entire trip. If the thrusters are at several points along its length and made to fire in unison so that the vehicle is made to move uniformly in the desired direction to correct for drift, it might be possible to reduce the structural loads placed on the vehicle.&nbsp; Bob Clark&nbsp;&nbsp; <br /> Posted by exoscientist</DIV></p><p>&nbsp;</p><p>1.&nbsp; This concept wasn't viable on usenet and nasaspaceflight.com and it isn't viable here neither.</p> <p>2.&nbsp; Not possible.&nbsp; The thrusters would not work and are not needed anyways..&nbsp; The LV can already manuever themselves.&nbsp; The attitude LV's fly at is related to the winds at that particular altitude.&nbsp; This is to reduce the stress on the vehicle.&nbsp; Thrusters would do the opposite and induce more stress by "forcing" the vehicle into a certain path</p> <p>&nbsp;</p> <p>Just drop this idea, it is not viable and won't work.&nbsp;&nbsp; It is not backup by any relevant physics, just a bunch of unrelated topics.&nbsp; Because you don't have physics or engineering knowledge, you can't see why it won't work. </p> <p>&nbsp;</p>
 
E

exoscientist

Guest
<p>&nbsp;Simply saying it won't work is not very convincing either.</p><p>&nbsp;&nbsp; Bob Clark<br />&nbsp; </p> <div class="Discussion_UserSignature"> </div>
 
C

Cygnus_2112

Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Simply saying it won't work is not very convincing either.&nbsp;&nbsp; Bob Clark&nbsp; <br /> Posted by exoscientist</DIV></p><p>&nbsp;You haven't shown that it will work. &nbsp;&nbsp; But anyways, there is a huge thread on Nasaspaceflight.com that proves it doesn't&nbsp; </p>
 
Status
Not open for further replies.

ASK THE COMMUNITY

TRENDING THREADS