June 03, 2013
Credit: Guy Norris/Aviation Week
Just over 50 years ago a high-powered Pontiac convertible charged across Rogers Dry Lakebed at Edwards AFB, Calif., towing a primitive lifting body. This month, Sierra Nevada Corp's (SNC) Dream Chaser, a descendent of the pioneering M2-F1, will repeat almost identical tests at NASA Dryden Flight Research Center as part of a program aimed at an orbital demonstration before 2017.
While the Pontiac and plywood-and-steel-built M2-F1 of 1963 have given way to a Ford truck and the advanced composite structure of the Dream Chaser, the aim of proving the viability of a lifting body for space transport is unchanged. Sierra Nevada's test comes as part of NASA's competitive Commercial Crew Program (CCP) to develop U.S. human space launch capability to low Earth orbit. It is widely viewed as providing the best chance yet for the first practical application of a design that can reenter the atmosphere and land on a runway using lift generated by the shape of the airframe rather than wings—the mode used by the space shuttle and Boeing's X-37.
Lifting-body development reached a dead end in the 1970s when the larger-scale requirements of NASA and the U.S. Air Force drove the designers of the space shuttle toward a winged reusable spacecraft. With the priority of the CCP focused on crew and smaller payloads, SNC revived NASA's HL-20 lifting-body design to develop the Dream Chaser, which is capable of carrying seven astronauts to orbit. The vehicle is designed to launch from Cape Canaveral atop a United Launch Alliance Atlas V 402.
Sierra Nevada is competing against alternative capsule designs developed by Space Exploration Technologies (SpaceX) and Boeing under a $212.5 million Commercial Crew Integrated Capability contract awarded in August 2012. The engineering test article (ETA) arrived at Dryden in mid-May from Sierra Nevada's Space Systems facility in Louisville, Colo., and is starting initial tow tests following reassembly and integrated systems testing.
The build-up to approach and landing tests (ALT) starts with a 10-mph tow behind a truck, followed by a gradual step-up in speed beyond 20 mph at intervals to 60 mph to “check the brakes and see how the guidance, navigation and control (GNC) operates,” says SNC Spacecraft Advanced Development director John Curry. Beyond this speed, the tow line will be cast off to demonstrate the ability of the steering and GNC system to track down the runway centerline. The Dream Chaser has a conventional wheeled main landing gear and a SpaceShipTwo-like retractable nose skid.
Other system checks prior to upcoming drop tests from a Sikorsky S-64 Skycrane include ground test of the flight termination and parachute deployment system. The Dream Chaser ETA, which flew a year ago in Colorado in a series of captive-carry flights slung below an S-64, is likely to continue ground taxi tests through July. ALT work, modeled after the initial flight-tests of the space shuttle demonstrator in 1977, is expected to start in August, with several drops set to occur from the helicopter hovering more than 10,000-ft. over the lakebed.
The flights will lead to high-altitude tests up to 40,000 ft. which will be conducted using a piloted space-capable flight-test vehicle now in initial assembly at Lockheed Martin's Michoud facility in New Orleans. If adequate funding is approved for the CCP, tow tests behind a C-17 could occur in late 2014.