Sierra Nevada Corp. And The Modernization Of Commercial Flight

SNC's Dream Chaser over Ellington Field. Image Credit: Sierra Nevada Corp.

SNC’s Dream Chaser over Ellington Field. Image Credit: Sierra Nevada Corp.

November 8, 2014 – Sierra Nevada Corporation (SNC) and partner organization RS&H, Inc. is investigating how to land the Dream Chaser spacecraft at commercial airports with minimal impact to existing operations, and how to integrate the spacecraft into current and future regulations and policies. The findings of their investigation thus far were presented at the Space Traffic Management Conference at Embry-Riddle Aeronautical University in Florida on November 5.

Louisville, Colorado’s SNC Space Systems is developing the Dream Chaser, an optionally piloted lifting-body vehicle designed to carry up to seven crew and/or cargo to and from low-Earth orbit (LEO). The Dream Chaser is designed for 3.5 days of independent flight and can dock with the International Space Station for up to 210 days.

The Dream Chaser spacecraft can land horizontally on nearly any runway with a minimum length of 8,000 feet and a minimum width of 150 feet. Additionally, all of Dream Chasers key subsystems (propulsions, autoland, aerodynamic control, and thermal control system) were developed with the goal of minimizing the need for specialized ground equipment. The Dream Chaser does not use any hazardous materials for operations, enabling safe and immediate access to the vehicle and crew.

SNC has coordinated landing site usage with the Shuttle Landing Facility (SLF) in Florida, Vandenberg Air Force Base in California, and Houston’s Ellington Airport in Texas, but the ultimate goal of Dream Chaser is to provide services to a broader commercial market. With this goal in mind, SNC has also initiated discussions and assessments with multiple landing sites around the world for both routine and emergency landings.

Most of the required Ground Support Equipment (GSE) can be temporarily deployed to the landing site ahead of a scheduled arrival. In some instances, locally available GSE such as an aircraft tug, tow bars, and cooling carts could be used.

A primary difference between the Dream Chaser and conventional aircraft is that the front landing gear of the Dream Chaser uses a skid instead of a rolling nose wheel. The ideal runway is constructed of concrete instead of asphalt so that it’s durable enough to withstand the vehicle’s existing skid material without causing unusual wear and degradation to the runway.

This difference also means that the Dream Chaser can’t taxi off the runway after landing like a conventional aircraft. The spacecraft will continue to occupy the runway until it’s properly safed and towed to a designated location at the airport. SNC is working to reduce the timeline needed for this, but currently estimate occupying the runway for 10-20 minutes post-landing. Some high-volume or single-runway airports could have a hard time suspending active runway usage for this length of time.

There are some other critical differences between the Dream Chaser and commercial airplanes. Space vehicles are not currently defined as aircraft and don’t fly in the same manner as conventional aircraft. The Dream Chaser descends from orbit as a glider, with both a very high velocity and a high sink rate.

As it descends, the spacecraft will pass through several different classes of air space, some of which may contain aircraft that aren’t in contact with air traffic controllers. Sierra Nevada will need to work closely with the FAA to reserve specific blocks of airspace to ensure appropriate traffic management. Air traffic can then be routed around the intended flight corridor.

Flight corridors will also be critical because of the potential for sonic booms to be heard on the ground. The Dream Chaser returns for landing with an airspeed in excess of Mach 5 above 100,000 ft, but slows to a landing speed of less than 200 knots. The FAA doesn’t have specific guidelines for an acceptable level of sonic boom during approach, but generally prohibits supersonic flight over land in the continental U.S. Further analyses needs to be done to understand the impact of sonic boom and trajectory shaping so that optimal flight paths can be developed. Issues such as population density and environmental sensitivity need to be considered.

A further consideration for Dream Chaser landings is the ability of the spacecraft to land autonomously as an unpiloted vehicle. A piloted return would meet the requirements of operating into an airport under current FAA policy regulations, but an unpiloted landing is an operation equivalent to an unmanned aerial vehicle. The use of UAV’s is an issue that the FAA is just beginning to address and policies for landing at public-use airports will certainly take time to evolve.

An alternative to public-use airports is the emergence of commercial spaceports. A number of existing and proposed commercially licensed spaceports exist and could potentially host Dream Chaser landings. Sierra Nevada and the FAA are currently considering the proposed Houston Spaceport at Ellington Airport for future landings.

There are a lot of benefits to landing at a licensed spaceport. During the licensing process, spaceports complete extensive environmental and airspace studies and in many cases, have approved flight corridors or arrival routes that can be used by spacecraft like the Dream Chaser. Additionally, stakeholders and the community are already familiar with proposed operations of space vehicles.

The SNC and RS&H, Inc. team will continue to study the impact of landing the Dream Chaser at public-use airports and commercial spaceports. With the ability to land at least once on each orbit around the Earth, the Dream Chaser will be able to deliver time-critical science experiments anywhere in the world. Sierra Nevada and the FAA will continue to work together to develop guidelines for landing that will help modernize commercial flight and revolutionize space travel to Low Earth Orbit.