DEEP-IN

DEEP-IN, also known as Directed Energy Propulsion for Interstellar Exploration, is a spaceflight propulsion concept that uses photonic laser propulsion with beamed power to propel a spacecraft in deep space. The concept, in development by NASA Innovative Advanced Concepts, is notable as the first concept for photonic laser propulsion backed by NASA. The concept is heavily derived from DE-STAR, a planetary defense satellite concept that also uses directed energy. The system is scalable and modular.

According to project lead Phillip Lubin, a scientist at University of California Santa Barbara, the project aims to allow spacecraft to accelerate to a significant fraction of the speed of light. Currently, research models suggest that using this technology, a satellite massing 100 kg could reach Mars in 3 days, a significantly shorter time than the current transit time. Additionally, a more massive crewed spacecraft, such as the Orion spacecraft, could reach Mars in one month, compared to the traditional requirement of around 5 months. However, News Ledge notes that this short transfer time would require a second array of lasers already existing on Mars to slow vehicles down for Mars orbital insertion.

Technology
DEEP-IN utilizes an array of small lasers to send a stream of photons which bounce off of reflectors on the spacecraft, lowering spacecraft mass significantly by not carrying propellant. Photon momentum would be translated to the spacecraft, and reflectors enable a theoretical twofold increase in momentum transfer compared to a blackbody surface. The project anticipates it could carry femtosatellites weighing grams at approximately 0.25 times the speed of light, and still have significant maximum speed on larger spacecraft.

Funding
The project, originally conceived and developed by researchers at University of California Santa Barbara, received approximately $100,000 USD in funding from NASA Institute for Advanced Concepts under a Phase 1 grant in 2015.