Extremely fast ejection mass

[nexium]

ESA recently used an ion engine to travel to the moon over a period of several months. We should soon be able to build an ion engine or equivelent which emits particles at much faster speed. This will greatly increase the thrust without increasing the ejection mass. Let's assume the craft accelerates at 1/10 th meter per second per second for ten million seconds = 2777 hours = 116 days. V = at = 1/10 times ten million = one million meters per second = 1000 kilometers per second = 3,600,000 kilometers per hour = 1/300 of the speed of light. <br />S = 1/2 at squared = 1/20 times 10 E14 = 5 times 10E12 meters = 10E9 kilometers = one billion kilometers. <br />We can now coast for millions of years at an average speed over 3 million kilometers per hour. About 116 days before our destination we turn the craft around and decelerate at about the same rate so we can land, orbit or do a slow fly by of our destination, about 2 billion kilometers from Earth/one of the moons of Uranus perhaps in about 232 days, which is much less time than using rockets and gravity assist maneuvers. Please comment, refute and/or embellish. Neil

 

[nikshliker]

this is the equivalent of saying that if we create a solar sail boat we can travel at the speed of light after a long acceleration process.<br /><br />it seems you are using newtonian physics for extremely high speeds in which they may not apply accurately.<br />as you approach higher speeds you wont be able to hold the same efficiency as you would at lower speeds.<br /><br />and never forget that there is resistance in space. even though it is small it isnt neglectible at higher speeds.<br />

 

[vogon13]

Have had an idea in mind for many years regarding propulsion concept, but not had training to evaluate its' practicality so if this is dumber than a box of rocks, let me know.<br /><br />I formerly worked in a hydraulics laboratory where the engineering team would design advanced hydraulic equipment, and I, the lowly grunt would get to blow up the stuff with a mighty hydraulic intensifier device. Now this piece of machinery was a big pile of outdated 1950s crappy brute force technology, but it could slowly pressurize a sealed container to 40,000 pounds per square inch, or until the sample failed (which is usually what happened). Now, what if I'm in space, and I have a small solar powered pump (a nice shiny new titanium pump instead of old piece of crap) and I pressurize a small sturdy container to 80,000 PSI that has a small diamond orifice that emits a tiny stream of water out the back of my spacecraft, what happens? I've seen firemen take a wild snake ride on a fire hose at 300 PSI and 200 GPM. I'm changing the equation to 80,000 PSI at micro gallons per second. I suspect there are some physics going on her that alter what happens but I will speculate the water coming out the diamond orifice will be traveling at the speed of sound in water, and remember this is 80,000 PSI water so I suspect SOS is higher than whatever it is at ambient pressure (4000 feet per second IIRC). What is my Isp with this arrangement? Am I better than chemical rocket but worse than ion engine? I dunno. Pumps are pretty reliable and at low flow rate here a pump capable of 80,000 psi wouldn't weigh very much. I know I need some photovoltaics to run electric motor on the pump. Is this system so obviously dumb that rocket scientsts are taught to laugh at this idea first day of college, or has no one done the math yet (sorry, I don't know how)? <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[nexium]

I also lack the training, but I think your propulsion system will have utillity when and if incredibly strong materials become available. With present materials, a mile of capillary tubing would be least mass to hold the 80,000 psi. I think the water can exit faster than the speed of sound in high pressure water, giving much higher ISP than chemical rockets. The limiting factor would be the temperature of the diamond orifice at which it would begin taking oxygen from the water to make carbon dioxide or carbon monoxide. That would quickly erode the orifice starting at about 900 degrees f, I think. Perhaps a silicon carbide, or boran nitride orifice could tolerate higher temperature.<br /> Model rocket makers sometimes use the 2 or 3 inch long cylinders of licquid carbon dioxide (for charging selzer water) to propel their models to an altitude of 100 feet or more, so your system is proven technology small scale. Neil

 

[vogon13]

IIRC my metallurgy class 25 years ago, many ferrous and titanium alloys have yield strengths in the 150,000 to 200,000 PSI range. I have seen small plastic hoses (kevlar) withstand 20,000 PSI repeatedly. By presurizing system small number of times, fatigue life of system should be sufficient to do the job, I just don't know if physics of system are practicle. <br /><br />I believe equipment with this capability is currently in use cutting materials like graphite epoxy composites, but I have been out of manufacturing world for many years, and really don't have a feel anymore what state of the art in high pressure fluids is. <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[Saiph]

I believe the chemical systems are better, and definetely safer during periods they are not in use. It's a matter of momentum really. I don't feel like doing the calculations right now, but you can create very, very high pressures, but you restrict the outflow to do so, these counteract eachother as far as propulsion goes.<br /><br />Nexium's newtonian analysis works just fine, 1/300th of the speed of light still produces very, very, small and completely insignificant relativistic effects. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>