XCOR XR-5K18 "Lynx" Main Engine Test
The Lynx Mark I
The Lynx Mark I is the initial flight test vehicle now under development at XCOR’s Mojave, CA facilities. This prototype vehicle will be used to characterize and flight test the various sub-systems of the craft including life support, propulsion, tanks, structure, aeroshell, aerodynamics, re-entry heating and other design elements. It will undergo a flight test program beginning in 2013. The flight test program consists of a traditional envelope expansion regime in which the vehicle is gradually tested to its full flight profile . The Mark I will be placed into commercial service after being licensed as a launch vehicle under Federal Aviation Administration rules. The Lynx Mark I will also be used to train pilots and crew for the Lynx Mark II. The Lynx Mark I is designed to achieve an altitude of 200,000 feet (approximately 61 km).

The Lynx Mark II
The Lynx Mark II will begin construction and assembly during the Lynx Mark I development program . The Mark II is the production version of the Lynx, servicing both the suborbital tourism market and all markets that make use of the Lynx’s internal payload volumes, such as microgravity and biotechnology experiments. The Lynx Mark II uses the same propulsion and avionics systems as the Lynx Mark I, but has a lower dry weight and hence higher performance than the Mark I. The Mark II incorporates a lightweight composite LOX tank integral with the aeroshell and several other key innovations that are proprietary to XCOR. Designed to fly to 350,000 feet (approximately 106 km), assuming certain payload weight conditions are met, the Mark II will take payloads and spaceflight participants to the edge of space and back. The Lynx Mark II is scheduled to enter flight service beginning in 2014.

The Lynx Mark III
The Lynx Mark III is a highly modified derivative of the Lynx Mark II that features the ability to carry an external dorsal pod with either a payload experiment or upper stage capable of launching a small satellite into low earth orbit. Total payload capacity for the external dorsal pod is 650kg. The Lynx Mark III is a different vehicle from the Mark II, featuring upgraded landing gear, aerodynamics, core structural enhancements, and features a more powerful propulsion package and other modifications needed to carry the extra weight aloft. A production time line for the Lynx Mark III is not set in stone, but we expect to roll this version of the craft out in 2015 or 2016.

Propulsion
Lynx propulsion is four X%-5K18 rocket engines each producing 12.9 kN (2900 lbf) vacuum thrust with kerosene and liquid oxygen propellants. Engine detail design began in autumn of 2008. The first hot fire test was conducted on 15 December 2008 and tests continue today.

CAPE CANAVERAL, Fla. - Lured by more than $5.7 million in state and local economic incentives and a skilled work force looking for jobs following the retirement of the space shuttles, XCOR Aerospace plans to manufacture and fly Lynx suborbital vehicles from the Kennedy Space Center (KSC) here.
The Aug. 23 announcement at KSC’s Visitor Complex is the second expansion plan unveiled by XCOR in as many months. The privately held firm, currently based in Mojave, Calif., will relocate its headquarters and development centrein Midland, Texas, leaving only an operations center, and possibly some flight test activities, in Mojave.

Lynx Development Plans with any production aircraft development program, XCOR has planned an initial test article, followed by several models of production vehicles that address different needs and markets.