W. E. Johns 
Death Rays of Ardilla [EPUB ebook] 

Tiger, Rex and the Professor return in book six of Captain W.E. John’s classic space adventure series!In their previous adventures, they encountered the planet Ardilla and its strange rays, which caused its inhabitants to develop thick skin in resistance. But reports are, the rays are getting stronger, and more deadly, and a mission to survey the planet has gone missing. The crew of the Tavona join the rescue mission — but what will they find?Meanwhile, a plucky young stowaway has hidden away on the ship, and finds himself seeing far more than he bargained for.It’s up to Tiger to get everyone home safely!