Alan Whitmore
Well-Known Member
- Joined
- Aug 27, 2013
- Messages
- 184
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- 523
>More seriously, the biggest problem you might have is oxidation on the grains (esp if they are white lightning loads). Before flying them, sand some of the surfaces just a little bit to help them light.[/QUOTE]
Everybody who has tried to fly an old AT White Lightning motor is familiar with the phenomenon, but I'm not sure that it is oxidation. The entire propellant grain is packed with oxidizer (AP) so why does it just happen at the surface? My current thinking is that it is related to the slightly hygroscopic (sucks up water) nature of AP, and involves some interaction between water, AP and maybe the metals in the propellant. The product, whatever it is, occupies more volume than the propellant that was there before (it swells), and that goober is dang hard to light, which is why "they" all recommend sanding or cutting it off before loading the motor. The involvement of water would explain why some old WL reloads are much more severely affected than others: The sealed plastic bags may suffer from small nicks or cuts, or they may experience light-induced depolymerization that would make some bags break down in one persons' storage area and not in another.
Alan Whitmore
Carrboro, NC
Everybody who has tried to fly an old AT White Lightning motor is familiar with the phenomenon, but I'm not sure that it is oxidation. The entire propellant grain is packed with oxidizer (AP) so why does it just happen at the surface? My current thinking is that it is related to the slightly hygroscopic (sucks up water) nature of AP, and involves some interaction between water, AP and maybe the metals in the propellant. The product, whatever it is, occupies more volume than the propellant that was there before (it swells), and that goober is dang hard to light, which is why "they" all recommend sanding or cutting it off before loading the motor. The involvement of water would explain why some old WL reloads are much more severely affected than others: The sealed plastic bags may suffer from small nicks or cuts, or they may experience light-induced depolymerization that would make some bags break down in one persons' storage area and not in another.
Alan Whitmore
Carrboro, NC