I'm pretty sure that either the "PERB" would need to be so massive to get enough of a pressure differential to cause lift that the FAA(USA) or CAA(UK) would require you to jump through very expensive hoops, and also that I struggle to think of a material strong enough to hold an almost-vacuum yet light enough to lift off! Also bear in mind that any payload and recovery system is likely to weigh upwards of a KG...<p>For my money: just buy a weather baloon for £15 on ebay and get a cheap cylinder of helium from your local welding supplier and you can be on the edge of space within a couple of hours!
We can trade height and mass for velocity - by dropping down things from ballon.<p>So I wonder if it's possible to attach pulley to ballon with huge lift (according to <a href="http://www.chem.hawaii.edu/uham/lift.html" rel="nofollow">http://www.chem.hawaii.edu/uham/lift.html</a> helium ballons have almost exactly 1 g of lift for 1 liter, which is 0,001 m^3). So ballon with 20 m of diameter will have over 4 tons of lift.<p>For 4 tons spherical lead weight with 0.62 m radius and 1.2 m^2 crossection and 0.47 drag coefficient dropped from 20 km this web calculator ( <a href="http://www.grc.nasa.gov/WWW/k-12/airplane/termv.html" rel="nofollow">http://www.grc.nasa.gov/WWW/k-12/airplane/termv.html</a> )
returns terminal velocity of 1505.569 m/s which is probably a little too big because it's hipersonic so drag coefficient will increase, but still, it's over 1/8 of escape velocity.<p>Now to get a very strong, frictionless :) rope. Attach the weight to this rope, put the rope throught pulleys system multiplying the velocity 8 times, and attach the second end of rope to payload (very light - sth like 50 kg for example) lying on ground.<p>Now fly the ballon to 20 km, leaving payload on the ground, drop the weight down, and look how your payload flies to space.<p>Will it work? Probab ly not, because of rope-pulley friction..
"I struggle to think of a material strong enough to hold an almost-vacuum yet light enough to lift off!"<p>Ah, no the whole point of the PERB is that it <i>doesn't</i> need a near vacuum -- just as much partial vacuum as is required to reduce its net mass to zero at the altitude where it currently is.