Some 1 million people suffer traumatic brain injuries annually. Concussion can cause inner ear damage that can cause dizziness, anxiety, depression, moodiness, balance problems and irritability, said Elizabeth Kirkpatrick, the physical therapist for the Fort Drum Traumatic Brain Injury Clinic. The three different forms of TBI—severe, moderate, and mild—all manifest …

Most spacecraft propulsion concepts can be classified into two categories: chemical and electric. Chemical propulsion relies on chemical reactions and can produce high thrust, but requires a large amount of fuel. Electric propulsion uses electromagnetic fields to accelerate ionized gases and is very fuel-efficient, but produces small amounts of thrust …