how could ion propulsion's thrust be amplified?

[bonzelite]

from what i know, ion propulsion technology has been around since the 1960s, but scarcely used. Deep Space 1 used it with great success, for example, yet the amount of thrust generated by the system was as if someone were blowing a feather from across the room, taking months and months to make any headway. <br /><br />how could this technology be hot-rodded? if it is a matter of "matter," ie, the amount of xenon supply v the rate at which this gas is ionized/ charge separated out the rear of the engine, couldn't they simply force more ions per unit of volume into the same area of the discharge plasma, ie, increasing current density? <br /><br />in short, in hot-rodding the technology, what would need to happen in order for ion propulsion to attain supersonic speeds? like 1 or 2 Mach? and have this throttling on-demand, like in jet engines, instead of gradually building up thrust over months of time?

 

[pyoko]

From http://en.wikipedia.org/wiki/Ion_engine<br /><br />"In the future it may be feasible to build nuclear fission reactors that can achieve multi-gigawatt electric power levels."<br /><br />Also, I believe ion drives have been used in far more than just one craft for maneuvering and keeping orbit. <div class="Discussion_UserSignature"> <p> </p><p> </p><p><span style="color:#ff9900" class="Apple-style-span">-pyoko</span> <span style="color:#333333" class="Apple-style-span">the</span> <span style="color:#339966" class="Apple-style-span">duck </span></p><p><span style="color:#339966" class="Apple-style-span"><span style="color:#808080;font-style:italic" class="Apple-style-span">It is by will alone I set my mind in motion.</span></span></p> </div>

 

[najab]

<font color="yellow">what would need to happen in order for ion propulsion to attain supersonic speeds? like 1 or 2 Mach? </font><br /><br />There's no sound in space.<br /><br /><font color="yellow">and have this throttling on-demand, like in jet engines,</font><br /><br />Ion engines <b>are</b> throttlable.<br /><br /><font color="yellow">instead of gradually building up thrust over months of time?</font><br /><br />Ion engine's thrust is instantaneous - turn on the current, turn on the gas - you got thrust.

 

[drwayne]

The value of an ion engine is that it in fact can produce thrust for a long period of time, meaning that a ship using it is in fact accelerating for a long time.<br /><br />Having thrust for a long time is like the magic of compound interest, eventually you can build up a lot of speed if you accelerate for long enough. Given an unlimited, even if small acceleration, one can acheive great speeds over long distances. That is the value of ion propulsion.<br /><br />Now, while it is true that you can make things bigger, so that you, in essense throw more ions overboard, you are going to add more mass to the vehicle (to power and run the augemented ion drive) in the process, and at some point you realy get to a point of diminishing returns.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[bonzelite]

najaB wrote:<br /><br />"what would need to happen in order for ion propulsion to attain supersonic speeds? like 1 or 2 Mach? <br /><br />There's no sound in space. <br /><br />and have this throttling on-demand, like in jet engines, <br /><br />Ion engines are throttlable. <br /><br />instead of gradually building up thrust over months of time? <br /><br />Ion engine's thrust is instantaneous - turn on the current, turn on the gas - you got thrust."<br /><br />i know there is no sound in space. i used Mach as a scale of velocity in general. sound has nothing to do with ion propulsion. 1 Mach will be about 760 mph at sea level. i should have not used the Mach scale.<br /><br />and i know ion propulsion can be "throttled." my question is more about the actual craft's velocity, not the exhaust of particles. to be more clear, i will restate the question: <br /><br />how can ion propulsion be made to generate more supersonic type g-force IMMEDIATELY? that is, how can you get an effect from ion propulsion that is FELT like a hard-pulling race car down the 1/4 mile? as if it were equipped with a jet enjine? in this new scenario, you have tremendous acceleration and velocity of the actual car, or jet, at once. not just the ion particles. i want the craft to go near 1100 ft/sec --immediately. <br /><br />i know that you can throttle ion propulsion, and i know you can accelerate the outgoing ions to near light speed. but you will not get the IMMEDIATE thrust, or in automotive terms, the feeling of torque, of G-forces, on the body or the actual space craft. a ion engine throttled to accelerate particles at thousands of miles per hour will, initially, feel like a gentle breeze blowing through a clothesline of bedsheets. this is why it takes months for velocity to build up. so how are probable ways to make it more responsive? <br /><br />thank you for making me think through the question more specifically. <br /><br />

 

[bonzelite]

perfect term: thrust to weight ratio. that is what i am wanting to increase. <br /><br />how would it be done? increasing the charge density of the plasma medium? if so, how would that be done without increasing the payload of xenon, or whatever, too heavily?

 

[drwayne]

An ion drive is much like any other conevntional rocket. It, in essense throws stuff out the back. Thats really all it is. It is physically equivalent to a gnome throwing tennis balls out the back.<br /><br />The number of tennis balls out the back, and the speed at which they are thrown determine the thrust. You throw more tennis balls, or you throw them harder, then you get more thrust.<br /><br />Once you turn an ion engine on, and it reaches equilibrium, it thrust is its thrust. It doesn't build trust or acceleration as a function of time. What the vehicle does is accelerate - and the velocity increases as a function of time.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[dragon04]

Is the thrust/weight ratio of ion engines linear?<br /><br />In other words, what I am asking is will ion engines as we currently know them always accelerate a vehicle at the same rate regardless of their size? <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[vogon13]

1 ounce of thrust will have proportionally less effect on a 100,000 ton spacecraft versus a 10 ton spacecraft.<br /><br />If I understand your question.<br /><br /><br /> <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>

 

[bonzelite]

"<br />An ion drive is much like any other conevntional rocket. It, in essense throws stuff out the back. Thats really all it is. It is physically equivalent to a gnome throwing tennis balls out the back. <br /><br />The number of tennis balls out the back, and the speed at which they are thrown determine the thrust. You throw more tennis balls, or you throw them harder, then you get more thrust. <br /><br />Once you turn an ion engine on, and it reaches equilibrium, it thrust is its thrust. It doesn't build trust or acceleration as a function of time. What the vehicle does is accelerate - and the velocity increases as a function of time."<br /><br />that is very interesting. but it does not answer the question really. if you had an ion propelled car and a 700hp corvette at the dragstrip, the corvette would win the race because it is faster off the line. the ion engine, despite having more "thrust" of the particles out the back, would barely move a sheet of paper if such paper were placed near the ion exhaust. and the ion car would sit there as the corvette ran low 11s on the 1/4 mile. <br /><br />that is the premise. <br /><br />so now, provided that ion propulsion can push particles out the back at tremendous velocities, how do we translate that into neck-snapping g-force, felt upon the craft itself, from rest? as in a drag racing car? or F-16?<br /><br />the idea is not very difficult to understand. and i proposed that the current density be ramped up, and that may actually create the "responsiveness" that i am asking about. but how would such a thing be implemented? this is a plasma dynamics issue. <br /><br />anyone have any other ideas? <br />

 

[vogon13]

Upping the voltage will accelerate the exhaust out the tailpipe faster, but now you need a bigger electrical supply to run the thing. Also, the acceleration grids are designed for a certain voltage and particle rate, so now they need redesigned too. Add a bigger fulel tank to match better with the upgraded thrust, and you lose more of your gains, but top speed of your craft is now much faster.<br /><br />Stick with ion drive for unmanned probes and develop patience.<br /><br />To step up a notch from ion drive, look into masss driver propulsion. <br /><br />And after that, the Vasimir.<br /><br />After you have tried the rest, come back to the Orion tent, 25,000,000 ton payloads to Alpha Centauri in 150 years.<br /><br />You know you want it.<br /><br /><br />Bwaa, ha ha ha!<br /><br /><br /><img src="/images/icons/wink.gif" /><br /><br /><br /> <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>

 

[igorsboss]

<font color="yellow">The number of tennis balls out the back, and the speed at which they are thrown determine the thrust. You throw more tennis balls, or you throw them harder, then you get more thrust.</font><br /><br />...and also the mass per ball. If you throw shot puts at the same rate and speed, you get more thrust than tennis balls.<br /><br />I think that's why they use Xenon - because each ion is quite massive.<br /><br />This brings me to another question: comet or asteroid deflection using an ion (or similar electric) thruster.<br /><br />The low thrust of an ion engine would be able to push a rubble pile better than an explosion could.<br /><br />Atomic energy could supply enough electricity, and we could probably build plenty of big ion engines, but we could never ship enough Xenon propellent to the asteroid to do any good!<br /><br />Deep Impact determined that the surface of comet Tempel-1 was comprised mostly of a very fine-grained dust. Surface dust seems very common.<br /><br />So, here is the question:<br />Can comet or asteroid dust be used as the propellent in an ion (or similar) thruster?

 

[bonzelite]

thank you, vog, and igor. that is some cool stuff. <br /><br />hmm. mass driver propulsion. and what is Vasimir? <br /><br />

 

[vogon13]

Vasimir is a variable mass flow ion drive. Kind of a hybrid between rocket and ion.<br /><br />Might not work, exhaust stream isn't neutralized and it may be attracted back to the vehicle, negating the propulsion effect.<br /><br /><br />But it might work, needs to be tested.<br /><br /><br /> <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>

 

[bonzelite]

right, current ion engines must neutralize the exhaust or it will do just as you said.

 

[drwayne]

"the ion engine, despite having more "thrust" of the particles out the back, would barely move a sheet of paper if such paper were placed near the ion exhaust. and the ion car would sit there as the corvette ran low 11s on the 1/4 mile. "<br /><br />The ion engine does NOT have more thrust, as you pointed out it would get dusted by a car. It does not have MORE thrust, it just maintains the thrust for a much longer time.<br /><br />Imagine for a minute that the race, instead of a quarter mile, is for a quarter of a million miles. The car will run out of gas after about 400 miles. Whatever speed it has, it what it will have. Much like a chemical rocket. Lots of acceleration, burns out quick. The ion engine will accelerate for a much longer period of time. It will eventually overtake the car, and leave it behind. It just needs a long track to do it over.<br /><br />The advantage of the ion drive does not show up in trips to the moon, it shows up on long trips, such as to other stars.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[bonzelite]

i was being led to believe, or just confusing myself, that i initially used "thrust" incorrectly. but you have cleared that up. i was using it correctly. <br /><br />and, yes, ion propulsion, over time, can accelerate the craft to insane speeds. imagine how fast the voyager spacecraft would be going now had they the payload and time to accelerate over the 25 years or so of their journey. <br />

 

[drwayne]

Thrust to me is equal to what I will refer to as the "force" acting on the vehicle at an instant of time. <br /><br />Some people start including elements of total impulse into things, which can confuse the simply confused portion of the crowd - like me.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[nexium]

I don't know if anyone has attempted to build a large ion engine. One million volts is sort of an upper limit for testing in Earth's atmosphere. Five million volts may be practical in the vacuum of space, but testing in space is very costly at present.<br />Super conductors make magnetic (instead of electrostatic) accelleration of the ions practical (likely) Again testing in space is costly, and there are few customers who are ready to put up big bucks to go to the Oort cloud, which is a mission where ion engines have big potential of superiority.<br />Worse several competing ideas may prove better than ion engines, so few are willing to spend big bucks on developing a big ion engine which may be ready to fly in ten years. Neil

 

[vogon13]

Mass driver would be an electromagnetic device. Base the technology on the linear induction levitating trains in Germany and Japan, and movem' on out!<br /><br />Make something that can fire slag or poo, and have a cheap reaction mass for your ride.<br /><br /><br /><br /> <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>

 

[bonzelite]

vog, could you explain a little more of the maglev technology adapted to mass driver. what do you mean?

 

[vogon13]

A linear induction motor could be adapted to accelerate a (crude example alert) steel bucket filled with rocks, instead of a train. At the end of the track, the bucket goes flinging off into the void at high speed, and the reaction forces impel the track (and anything attached to it) in the opposite direction. If you want to improve the performance of the system, just make the track longer.<br /><br />The force to accelerate a 100 ton train car, would instead be concentrated (in this case) in a 50 pound bucket of rocks. It would be going far faster than mere rocket exhaust.<br /><br />And away you go!<br /><br /><br /> <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>

 

[bonzelite]

a steel bucket filled with rocks, or "rockets"? you said both.

 

[vogon13]

Oops!<br /><br />Thanx for pointing that out, rocks of course. <br /><br /><br />Did you ever see the Kliban cartoon:<br /><br />Carp - Carpathian<br /><br />Christ - Christian<br /><br />Rock - Rockettes<br /><br />?<br /><br /><br /><img src="/images/icons/laugh.gif" /><br /><br /><br /><br /> <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>

 

[bonzelite]

OMG! yes! i LOVE Kliban! i was raised on him. i'm sick and warped and i immediately became drawn to him: <br /><br />"jelly"<br /><br />"belly" <br /><br />"rotten and smelly"<br /><br />LOL! <br /><br />"the callous sophisticates laughed at judy's tiny head." <br /><br />his genius lives on. <br />