The phrase "nuclear energy" conjures images of large steaming towers or Tony Stark's arc reactor from the iconic "Iron Man" movies. But two Seattle-based startups are designing nuclear technologies small enough to pick up and carry that, thanks in part to buy-in from the Defense Department, they hope will fuel a new generation of spaceships.

Seattle's Avalanche Energy and Ultra Safe Nuclear Corporation received undisclosed amounts of funding from the Pentagon's Defense Innovation Unit in May to further develop two different approaches to small-scale nuclear power.

Avalanche is pushing the boundaries of nuclear fusion while Ultra Safe aims to revolutionize nuclear radioisotope batteries, like those that power Mars rovers. Both companies are expected to deliver functional prototype spacecraft to the Pentagon by 2027.

"Nuclear is an interesting area because traditionally that's been mainly in the realm of government," said U.S. Air Force Maj. Ryan Weed, the program manager for the Defense Innovation Unit's nuclear propulsion and power program. The unit—the Pentagon's outpost in Silicon Valley—works exclusively with private sector companies to adapt emerging technologies for military use.

After six decades of materials science research, nuclear fuels are relatively safe and are being embraced in the private sector.

Sleep is important for our health and well-being, and bad sleep can negatively impact our attention span, memory, decision-making skills, creativity and judgment.

Astronauts living in zero gravity with an artificial day-night cycle have trouble maintaining a natural circadian rhythm and normal sleep patterns. In fact, sleep is what astronauts complain about the most.

To avoid the negative short- and long-term side effects of poor sleep, Aarhus University's Centre for Ear-EEG has developed a technology that can monitor an astronaut's sleep in a non-invasive and discreet manner via so-called "ear-EEG" (ear-ElectroEncephaloGraphy). The technology, along with Danish astronaut Andreas Mogensen, will travel to the International Space Station ISS to examine the differences between human sleep patterns on earth and in space.

The project is called "Sleep in Orbit."

"Sleep is a kind of biomarker for our health and well-being. In fact, a great many diseases also impact the way we sleep, including a wide range of psychiatric disorders and neurodegenerative diseases.

Astronauts that have returned after spaceflights over three months may show signs of incomplete bone recovery even after one year on Earth, but adding in more resistance-based exercises during spaceflight may help limit bone loss. The small study, published in Scientific Reports, on 17 international astronauts found that while the shinbone partially recovers, the sustained bone losses after one year are equivalent to ten years of normal age-related bone loss on Earth.

Steven Boyd and colleagues imaged 17 astronauts (14 male, three female) before spaceflight, at return to Earth, and after six and 12 months of recovery. They conducted bone scans on the tibia (shinbone) and radius (forearm) to calculate the resistance of the bone to fracture (failure load), bone mineral in the bone tissue, and tissue thickness. The authors also recorded exercises such as cycling, treadmill running and deadlifting completed by astronauts in-flight and post-flight.

One year after flight the median results for 16 of the astronauts showed incomplete recovery of the shinbone. Median shinbone failure load, measuring bone strength, was reduced by 152.0 newtons from 10,579 newtons at pre-flight to 10,427 newtons after one year.