Dr. Grubb grew up on the west side of "Boeing Hill," near the town of Mukilteo in Washington state, watching various aircraft being tested and flown throughout his childhood. He always knew when they were testing jet engines because of the sound coming from the test stands. He and his family eagerly watched the launches of Mercury and Apollo spacecraft throughout the early years of the NASA program. Later he would make time to watch Shuttle launches as well. At first, Dr. Grubb wanted to be a fighter pilot, but his nearsightedness prevented him from passing the vision test.
After changing his goal from pilot to physician, he attended the University of Washington State for pre-med courses. He took a break from pre-med studies to pursue a bachelor's degree in Nutrition/Food Science (1973-75) before attending the University of Southern California, School of Medicine (1975-79) in Los Angeles. He completed his internship at UCLA/Cedars Sinai (1979-80), followed by his residency at Antelope Valley Hospital Medical Center/UCLA Family Practice Program, in Lancaster, CA. Dr. Grubb became a fellow of the American Board of Family Practice in July, 1982.
He entered into a solo medical practice in the high desert area of California in 1982, not far from Mojave, which placed him back into an active aerospace location, close to experimental aircraft at Edwards AFB, the Voyager craft, and now SpaceShipOne.
Dr. Grubb was chairman for the Department of Family Medicine at Antelope Valley Medical Center from 1986-2000. He served as medical director for Sage Medical Group from 1993-99 while maintaining his own practice. In addition, he was a diplomat of the American Board of Family Practice from 1995-2005.
Dr. Grubb's hobbies include gardening, skiing, sailing, singing, an interest in cosmology and quantum mechanics theories, and, when he has a moment, reading a good book.