The initial Advent concept used parallel (side by side) stages with the payload on top of the orbiter stage. This concept facilitated ocean operations, making it easy to mount the orbiter stage onto the booster stage. The payload was then to be loaded onto the orbiter stage. However, recent analysis indicates that series stages; the orbiter and payload on top of the booster, reduces aerodynamic interference and is likely to reduce cost more than it increases ocean operations cost. The early configuration may be altered as the analysis is more thoroughly studied.

An engineering prototype model has been used for aerodynamics testing. A radio controlled flight test model is scheduled for tests.

The Xprize entry is shown without the outer cover. The propulsion system for the ANSARI X PRIZE was tested in June 2004. The photograph shown is derived out of the video recording of the test. Two successful engine runs were accomplished. However, an oxygen servicing line was overheated by the rocket plume, causing the line to rupture. The resulting fire damaged the Xprize entry to the extent that repairs could not be made before the prize was won by Bert Rutan.

An engine test at NASA’s Stennis facility in November of 2006 was successful.  However, the test series was terminated because of an oxygen leak.  The leak was apparently the result of dynamic boiling of the oxygen.

The third Advent engine was fabricated using only fuel for cooling the engine combustion chamber and nozzle.  The test of that engine was terminated because of ingition failure.  Previous engine tests, using the same type ignition system functioned properly.  However this engine employed a “swirl” feature to provide cooler and higher density gasses to be adjacent to the chamber wall, thus requiring less cooling by the incoming fuel.  Apparently the swirl feature concentrated the heavy oxygen vapor in the ignitor area.  Without fuel in that area, ignition did not occur as planned.  Fuel and oxygen mixture was discharged into the test area for about two seconds.  Ignition at that time resulted in a very “dynamic” environment.  Development of the engine has been very significant in spite of very limited access to appropriate test facilities. An automatic shutdown system could have avoided the “dynamic” environment. An investment in facilities can be very cost effective.