What exactly is suborbital anyway?

A suborbital vehicle goes into the space environment (100Km or 60 miles are commonly considered borderlines to space) and returns without going into orbit around the earth. Generally, a suborbital craft gets a boost from a rocket and then simply coasts unpowered up and back down on a ballistic trajectory for most of the rest of its flight as shown by the the graph below:

Credits: 2004 Report on Space Transportation Developments and Concepts
Typical trajectory for an X PRIZE or commercial suborbital vehicle

Historically, suborbital space has been explored with unmanned, expendable sounding rockets. Completely reusable, manned suborbital vehicles will fully exploit the potential of this coastal region of outer space.

The following graph gives another view of the relative altitudes involved for various flying machines. (X Prize Vehicles mark indicates the 60 mile altitude that is the typical target for most manned suborbital vehicles.)

Credits:Suborbital Reusable Launch Vehicles and Applicable Markets, October 2002
Relative altitudes for various aircraft, suborbital, and orbital vehicles

What Does a Manned Suborbital Rocket Vehicle Look Like?

There are many different designs for reusable manned suborbital vehicles. The most famous is Burt Rutan's White Knight/SpaceShipOne combination. Other vehicles in development include single-stage vertical takeoff and powered vertical landing, single stage horizontal takeoff and landing, vertical takeoff and parafoil landing, as well as other designs and configurations.

The SpaceShipOne system uses a two stage, air-launched approach. The White Knight takes off from a runway with the SS1 connected beneath it. The White Knight releases the SS1 at an altitude of around 15 Km (50,000 ft) The SS1 then fires its rocket and flies to over 100 Km (62 mi). The SS1 falls back into the atmosphere and glides to a landing on the runway.

This proposed single stage vehicle from Armadillo Aerospace would take off vertically and land vertically under rocket power.

The Xerus vehicle, under development by XCOR Aerospace, would take off and land horizontally in a single stage mode.

See this 2005 study report (pdf) from the FAA for a review of various suborbital vehicles now in development. Check out also some of the companies on this suborbital vehicle companies link list.

Why Fly Suborbital?

The Frequently Asked Questions section discusses applications of suborbital vehicles. This 2005 study report (pdf) from the FAA also looks at markets that will be served by manned suborbitals.

This article looks at how reusable manned suborbital vehicle development could provide an incremental path to low cost orbital space transportation.

For an overview of developments in the field of suborbital spaceflight, see this report by Jeff Foust: Suborbital’s ascending trajectory: Once dismissed as a dead end, reusable suborbital spacecraft are finally getting respect from the Space Review April 14, 2003.

See also Pat Bahn's article Revolutionizing SpaceFlight, which originally appeared as an editorial page article in the industry newspaper Space News.

Other reports, articles, and studies about suborbital spaceflight are available via our Resources sections. See also the Web Links for pointers to various websites that deal with suborbital space topics.

Modified April 7, 2005