Unrelated to the topic, but thought this was interesting anyway.
DARPA Subterranean Challenge
https://subtchallenge.com/
>> Drive novel approaches and technologies to allow warfighters and first responders to rapidly map, navigate, and search dynamic underground environments.
>> Teams in the Systems track will compete for up to $2 million in the Systems Final event, with additional prizes available for self-funded teams in each of the Systems Circuit events. Teams in the Virtual track will compete for up to $1.5 million in the Virtual Final event, with additional prizes for self-funded teams in each of the Virtual Circuit events.