I have been thinking. If you had very big surface area plane with 240 ft span and had Solar cells on it and batteries...and unlike a Solar Impulse you would be using both sun and batteries to propel the craft on at very high altitude you brake the sound barrier just like Alan Eustace did at 120 000...

P-3 Orion P3 Orion Service Digest Magazines for sale

I have three service digest available for sale:
Issue 1, November, Decmeber 1962
Issue 16, June 1967
Issue 11, March 1965

$49, firm for all 3

Inside pages in excellent condition; outside covers...