Ion engine - escape earth?

[rlock]

For anyone who is interested in difficult maths.<br />If we had enough power, and a light enough craft, could we escape earth from an altitude of 40,000 metres? I ask because JP Aerospace is suggesting just that, and i would like to know if it is posable. Just for reference, to achieve Low Earth Orbit, you need to get to at least 7500 metre/second.<br />Does anyone know the maths that you would need to work this out? If so, please tell me. I am especially interested in the maths behind the ion engine because that seems to be the root of the problem.

 

[vogon13]

If thrust > drag for your vehicle, it'll work. Computing hypersonic drag of the typical irregularly shaped satellite is most likely a bear. <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>

 

[tap_sa]

<font color="yellow">" Computing hypersonic drag of the typical irregularly shaped satellite is most likely a bear."</font><br /><br />Here's an accurate estimate for JPA's two mile long orbital blimp: <i>gargantuan</i>

 

[nexium]

Getting to low Earth orbit and escaping Earth are different math problems, but I can't help with either. A rocket craft designed for single stage to orbit = SSTO can likely escape Earth's gravity and reach The Moon if launched from 40,000 meters, with modestly different programing.<br /> Present ion engines = no, but several (sort of like ion engines) are on the drawing boards that may be able to go most anywhere in the Solar system, starting from 40,000 meters altitude. Neil

 

[grooble]

Can't the ION engines just have their speed increased? Make the pulses faster, or add more fuel or make them stronger somehow.

 

[nexium]

Yes, all three, but the engine gets bigger and heavier. Designers will likely be flying better ion engines in a year or two. For very long missions, much faster mass ejection can allow more thrust with less fuel/more correctly called ejection mass. Large amounts of electricity, and/or super conducting magnets may be needed. Neil

 

[grooble]

What sort of ion engine could you build with 200mt weight allowance?

 

[nexium]

An ion engine that weighs 200 metric tons would work poorly as we need to increase performance gradually to avoid bad errors. In 50 years we may have a 200 metric ton ion engine powering a probe past Uranus at 0.1 c and still accellerating, but only if we build several lesser ion engines in easy steps first. Ion engines have a lot of potential. Neil