Space on Earth: a visit to a wooden hangar where the future is being born.

• Author: Doherty, Brian
• Position: XCOR Aerospace - Company overview - Essay

THE SIGHT IS a wickedly thin line of shimmering and vibrant pale green. The sensation is a warm pulse. The sound is muffled to insensibility by high-grade ear protection. On my tape recorder later, however, I hear it: a sharp-edged roaring whoosh that strains my speakers to the breaking point.

It's an honest-to-goodness rocket engine, designed to shift a spaceship floating in weightless suborbit in order to give a passenger a different viewpoint, or to position the craft for safe re-entry to Earth's atmosphere and gravity well. It's burning a proprietary, nontoxic fuel mixture.

I'm at the Mojave Spaceport--the private general aviation airfield where SpaceShipOne, the first private vehicle to zip twice between space and back, first took off in 2004.That's the same year that Mojave became certified by the Federal Aviation Administration (FAA) as the nation's first private "spaceport," certified to send vehicles and people out of this world. Seven years later, more than a handful of commercial space companies operate out of this sprawling complex of runways, hangars, and airplane bits, and it's no longer the only private spaceport in America.

I'm a guest of Michael Massee of Mojave Spaceport tenant XCOR, a 30-employee company founded in 1999 to help build an active space transport and exploration industry.

XCOR has already built two successful rocket powered airplanes, the EZ-Rocket and the X-Racer. The company's EZ-Rocket sits in one comer of the hangar, showing none of the strains one might expect of a homebuilt airplane shot around by rocket power. Massee shows me the toggles that activated the rocket, the fire suppression switch, even the fuel dump. XCOR has launched dozens of rocket plane flights and thousands of rocket engine firings without once experiencing a "hard start" (rocketeer euphemism for "explosion") or other serious harm. XCOR investor Lee Valentine, also chairman of the board for the Space Studies Institute (an exploration advocacy group), boasts to me of XCOR's rocket engines' unusual longevity and reusability.

XCOR's main goal now is building and flying the Lynx, a suborbital vehicle to take tourists, experiments, and small satellite payloads out of this world. The company is also developing a new fuel pump, which will also be used by United Launch Alliance, a Boeing-Lockheed Martin joint venture that does most of the heavy private rocket-launch service these days.

The night before this XCOR visit I attended the first Los...