Sierra Nevada Corporation (SNC) may not have been awarded a multi-billion dollar commercial crew contract by NASA, but that isn’t stopping the company from moving forward with plans for their Dream Chaser. The fact is the spacecraft’s unique lifting-body winged design offers numerous potential applications that no other existing spacecraft can, and the aerospace community is taking note regardless of NASA’s decision to select two capsules for the same job. Earlier this month SNC and partner organization RS&H, Inc., presented findings regarding the challenges and opportunities of landing Dream Chaser at public airports during the Space Traffic Management Conference at Embry-Riddle Aeronautical University (ERAU) in Daytona Beach, Fla., summarizing the vehicle’s capabilities and describing their efforts to land at commercial airports with minimal impact to existing operations.
Dream Chaser’s ultimate goal is to provide commercial services to a broader commercial market, and at the conference, which was held on Nov. 5, 2014, SNC discussed in detail how they plan to ensure that their reusable “spaceplane” meets safety and environmental requirements, as well as operates within, or exceeds, existing and future procedures and policies.
For starters, the vehicle, which can fly with or without crew, does not require hazardous chemicals for its operation, and therefore can land at any suitable runway at least 8,000 feet long, anywhere around the world without requiring specialized equipment. With a propulsion system fueled by Nitrous Oxide and propane this also means immediate access to the spacecraft after landing, with only 10-20 minutes needed to exit the runway and keep conflicts with other aircraft using the same area to a minimum. For a nominal (planned) landing this might not mean much, but in an emergency abort (unplanned) scenario such quick access to Dream Chaser would allow other airport operations to proceed with minimal or no impact from the spacecraft’s unexpected arrival.
That fact alone opens the door to broader landing locations and opportunities, allowing for frequent deorbit opportunities to landing sites in the United States and the ability to perform runway landings on every orbit. United States’ landing sites will also take priority over other runways around the world should Dream Chaser become an operational reality too, unless otherwise directed by mission needs or emergency demands.
As outlined by SNC: “The reentry cross-range capability of 1,100 nautical miles (nmi) for the Dream Chaser exceeds Space Shuttle performance and allows the vehicle to maintain at least one runway landing opportunity every orbit. 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. SNC has also initiated discussions and assessments with multiple landing sites around the world.”
Dream Chaser’s unique ability to utilize public airports could prove particularly useful should an abort ever be needed during launch. The space shuttle always had a “Return To Launch Site” (RTLS) capability, but some veteran shuttle workers who maintained the fleet sometimes joked about RTLS as being more so peace of mind knowing that some kind of abort option existed, rather than having none. Some even argued that a shuttle RTLS abort would likely not work, simply because the SLF near the launch site was the only option; no other runways in striking distance could accommodate the shuttle, and thankfully we never had to find out.
However, a launch-abort scenario for Dream Chaser would work up and down the U.S. East Coast because the vehicle offers a continuous runway landing capability from Cape Canaveral Air Force Station Space Launch Complex-41 through the Atlas-V/Centaur launch vehicle trajectory (SNC contracted ULA and their Atlas-V some time ago to launch Dream Chaser on its first orbital flight test in November 2016).
“The Federal Aviation Administration (FAA) participates in regular collaborative dialogue with the Dream Chaser program and assists SNC in pre-coordinating emergency landings with identified landing sites,” noted SNC in their presentation. “For ISS flights, SNC and the FAA will distribute Dream Chaser System operations documentation to all identified emergency landing sites, ensuring familiarity with the spacecraft in the event of an emergency landing.”
Landing is one thing, but getting off the runway quickly is another issue. Dream Chaser does not have the ability to taxi like conventional aircraft, so landing at a public runway cannot be approached in the traditional sense. To overcome this, SNC has devised an efficient, new approach that is time-constrained in order to minimize time on a runway to allow airports to resume normal operations as soon as possible with minimal impact.
For example, gone are the days of crews getting off their vehicle while still on the runway, such as was done for all of NASA’s space shuttle returns. Instead, SNC’s approach is to have the crew remain on Dream Chaser until it is towed to a designated location off the runway where there are no time constraints to conduct all of the post-flight tasks. Alternatively, SNC could—after the vehicle is deemed safe to approach—begin three simultaneous operations, where one team attaches the appropriate ground support equipment (GSE) while another prepares the vehicle for towing. At the same time a crew member would be taking photos of pre-determined hardware to support post-landing evaluation and inspections.
While getting Dream Chaser off the runway would only take 10-20 minutes, post-landing operations for an uncrewed vehicle would be a little trickier, because a cargo-only Dream Chaser would be required to have a Flight Termination System (FTS), or self-destruct, which is usually ordnance-based. However, SNC is looking at alternative FTS options that eliminate an ordnance-based system all together.
Although SNC’s vehicle will be able to utilize many public airports, it can’t land on just any runway; there are specific infrastructure and operational requirements that must be supported, such as using runways made out of concrete instead of asphalt. Dream Chaser’s front landing gear uses a skid instead of a rolling nose wheel, and tests of the landing skid at Edwards Air Force Base in California have demonstrated that concrete runways are durable enough to withstand the vehicle’s existing skid material without causing unusual wear and degradation to the runway.
“During the campaign, the nose landing skid imparted no damage to the runway, striping, or runway centerline lighting,” noted SNC. “Additionally, no damage was done to the runway when the test configuration left main landing gear did not properly deploy during an atmospheric flight test. The ground tow and flight testing proved that the skid material is compatible with existing concrete runways.”
Airspace coordination is another key factor in any future Dream Chaser landing at public airports. The vehicle’s high velocity and a high sink rate return (like shuttle) renders it incompatible with typical aircraft operations and requires special handling from Air Traffic Control facilities. All commercial aircraft operating at altitudes between 18,000 feet and 60,000 feet are required to operate on flight plans generally under Instrument Flight Rules (IFR) requirements and must be in contact with FAA air traffic controllers. Below 18,000 feet, many aircraft are not on flight plans with a mix of IFR and Visual Flight Rules (VFR) operations and, depending on the geographic area, may not be in contact with air traffic controllers.
With that said, specific blocks of airspace must first be identified before Dream Chaser is cleared to land. Letters of Agreement among the various controlling agencies will establish the necessary procedures for reserving airspace and ensuring appropriate traffic management, and with a pre-authorized reservation in place, commercial air traffic can be routed around the intended flight corridor until Dream Chaser lands.
Other considerations are also being looked at as SNC moves forward with plans for Dream Chaser—everything from public safety, to FAA licenses, to the fact that an uncrewed Dream Chaser would technically be considered an unmanned aerial vehicle (UAV), for which the FAA is currently evolving its policies. Another obstacle is the fact that, while federal regulations prohibit most airports from favoring one type of aircraft over another, space vehicles are not currently defined as aircraft. Regulations also require a number of reviews be completed to demonstrate safety and compatibility with the reentry site, including a policy review, a safety review, a payload reentry review, and an environmental review.
Sonic booms over populated areas is another concern that SNC is looking at, because Dream Chaser will return with an airspeed in excess of Mach 5 above 100,000 ft, significantly slowing on the flight profile with a landing speed of less than 200 knots. While waivers can be granted, supersonic flight over land is generally prohibited by the FAA, and in order to determine the acceptability of the proposed landing flight corridor an analysis must be made of the potential for sonic booms to be heard on the ground. The FAA does not have specific guidelines for the level of sonic boom that is acceptable during the approach for landing, and approval depends on issues such as population density and environmental sensitivity of the overflight area.
The future of SNC’s Dream Chaser may be uncertain, but one thing is for sure: The company is moving forward with their plans to see Dream Chaser fly, regardless of NASA’s decision to select Boeing and SpaceX capsules for $7 billion in commercial crew contracts. The company has already built global partnerships with 21 space agencies around the world and is continuing to build a solid foundation and path forward for Dream Chaser, with or without NASA. More approach and landing (ALT) tests are on the horizon, and the company still has a launch date atop an Atlas-V rocket from Cape Canaveral, Fla., in November 2016. The question, however, is who will their primary customer(s) be, if any? We will all have to wait and see.