Things are getting desperate for the 12 boys and their football coach, who have been underground since June 23. It is being built from the liquid oxygen transfer tube of a Falcon rocket hull.
Musk said on Twitter the aluminum sub would be tested until Sunday midafternoon California time before being placed on a 17-hour flight to Thailand.
The 12 boys and their coach had been trapped in the Tham Luang Nang Non for more than two weeks now.
"Light enough to be carried by 2 divers, small enough to get through narrow gaps". One rescue diver, Petty Officer Saman Gunan of the Royal Thai Navy, died on Thursday.
"SpaceX & Boring Co engineers headed to Thailand tomorrow to see if we can be helpful to govt", Musk tweeted. Making matters worse, most of the young boys do not know how to swim.
Teams of Thai and global divers have since supplied them with food, oxygen and medical attention, but there are mounting concerns about the oxygen level in the chamber, which officials said had fallen to 15%.
The boys, aged 11 to 16, have practiced breathing in scuba masks but they have not been fully trained to handle the daunting cave system.
Meanwhile, rescuers have a dwindling window of opportunity, with forecasters predicting the return of heavy monsoon rains in the coming days, effectively sealing off the cave until October.
The tubes and pods are being built in the U.S., a spokesman said.
The operation to rescue 12 boys and their coach from a flooded cave in Thailand kicked off early on Sunday, a couple hours after Musk had predicted his project would be complete and nearly a day earlier than he said he would be able to bring the sub to Thailand.