As Sierra Nevada Corporation (SNC) continues forward with efforts to develop numerous mission scenarios for its Dream Chaser space plane, a study – in collaboration with Stratolaunch Systems – expands on the scaled-down version of Dream Chaser launched into orbit via the air-launch vehicle for a variety of mission including ISS emergency crew rescues and micro-gravity research missions.
Dream Chaser’s future
With Boeing and SpaceX receiving the coveted commercial crew transportation contracts to ferry NASA astronauts to and from the International Space Station (ISS) beginning in 2017, Sierra Nevada Corporations’ Dream Chaser (DC) space plane was left out in the cold.
While the company has filed a formal appeal pertaining to the specifics of that commercial crew contract selection process, SNC has also begun studies and initiatives to further the DC cause and market the spaceplane’s multi-use capabilities for the commercial and government space environment – including the spaceplane’s unique characteristics that are not shared by any other current or in development government or commercial space vehicle.
Part of this campaign involves Sierra Nevada Corporation’s joint study with Stratolaunch Systems to pair DC with that company’s air launch services vehicle.
According to the study document released by Vulcan Aerospace Corporation and SNC, “(the companies) have collaborated on a space transportation architecture, utilizing the Stratolaunch aircraft as a launch platform and the Dream Chaser spacecraft as the payload.”
This configuration, according to the study, will result in “unmatched mission flexibility and capability,” including ISS rescue, suborbital research, and suborbital point to point transportation.
Moreover, the exact architecture of this launch system would actually be a variant of the commercial crew DC vehicle, not the full scale model that was under development as part of NASA’s commercial crew transportation contract process.
In fact, both companies state in the research document, available for download on L2, that pairing DC with a Stratolaunch platform contains “numerous technical and programmatic advantages … that are unique among the available spaceflight offerings.”
Dream Chaser and Stratolaunch:
In all, the combined Stratolaunch and scaled-down version of the DC would weigh 1.3 million pounds at take off with the Stratolaunch air carrier vehicle reaching a wingspan of more than 380 feet.
This would require that the Stratolaunch carrier aircraft have a runway of at least 12,500 feet in length for take off and landing.
While there are numerous runways at commercial airports in the United States, most renderings of the aircraft show it using the former Shuttle Landing Facility (SLF) at the Kennedy Space Center (KSC) as its take off and landing point.
As part of this launch configuration, the scaled-down version of DC would be hosted in the forward portion of an Orbital Sciences rocket propelled launch vehicle.
According to the Stratolaunch and Sierra Nevada Corporation document, “Orbital Sciences is leveraging their launch history with the Pegasus system to develop this new air launch vehicle for Stratolaunch.”
This rocket propelled multistage launch vehicle would be nearly 120 feet in length and would drop-launch from the bottom of the Stratolaunch carrier aircraft at an altitude of 30,000 feet.
Mounted to the forward end of this rocket propelled multistage launch vehicle would be the scaled-down version of DC.
In this configuration, DC would be a 75 percent sized variant of the DC spacecraft designed as part of NASA’s crew transportation contract program.
As noted in the study document, “even with a smaller scale, the scale DC can achieve a comparable mission length to the commercial crew variant.
“This performance is achieved by using flight day one (FD1) launch opportunities (to ISS), operational optimization of redundant systems, and multiple de-orbit opportunities, per day, to Continental United States (CONUS) landing sites.”
The scaled version of DC would also use “common propellants between its abort motors and on-orbit maneuvering engines to maximize its orbital delta-V capability.”
As previously reported by NASASpaceflight.com, part of the positive design aspects of DC relate to its ability to land on any commercial runway in the world within 2.5 hrs of an on-orbit emergency or immediate mission termination scenario with limited disruption to commercial air transportation at that airport as well as immediate access to cargo and crew aboard the vehicle following landing.
This ability to not only reach the ISS on Flight Day 1 (FD1) – as well as to perform immediate de-orbit operations – provides what the research document terms as a “flexible niche market capability.”
The 75 percent Dream Chaser:
In undertaking the study for this type of the launch system for the DC spacecraft, Vulcan and Sierra Nevada Corporation looked at how to reconfigure the DC to meet the Stratolaunch capabilities.
The study determined that a 75 percent reduced sized DC was the most efficient size for a Stratolaunch configuration while still maintaining mission parameters and internal pressurized volume of the DC to meet critical mission needs.
Those needs specifically included the accommodation of three crewmembers in a seated position for launch, entry, and landing operations as well as the associated systems needed for human missions aboard the DC.
In total, the scaled version of DC was “scaled linearly to 75 percent to maintain the shape and curvature of the outer mold line (OML).”
This version of scaling allowed for the continued use of the aerodynamics databases created as part of the 100 percent DC model under development as part of the commercial crew contracts program while still maintaining enough internal pressurized volume to accommodate a maximum of three crewmembers.
Under the scaled approach, the DC would still use the same subsystems as the 100 percent variant very end and would “retain many identical subcomponents or mechanisms and leverage as much analysis and materials as feasible, with larger components requiring scaling and some modifications.”
Though the research document does not state anything about how DC – in her scaled-down version – would dock with the International Space Station considering any berthing mechanism used to connect DC to one of the ISS berthing ports can’t be scaled, the document does make several references to ISS rescue and resupply missions – which would in someway indicate that certain hardware elements contained aboard DC would not be scaled down.
Exactly what this would mean in terms of the positioning of the berthing mechanism on DC for attachment to the ISS is unclear. It is possible that the berthing mechanism would remain on the aft of the spacecraft – as current renderings of the scaled DC version for ISS operations still show the docking adaptor mounted on the aft part of the vehicle.
In total, the scaled version of DC would be 22.5 feet in length, contain a fin tip-to-tip wingspan of 18.2 feet, be able to carry a maximum of two crewmembers to ISS and three crewmember LEO (Low Earth Orbit) destinations for due East launches, and maintain a 92 percent annual launch availability rate for FD1 rendezvous with the ISS.
The internal pressurized parts of DC’s scaled design would be comparable to the internal volume of the Apollo command module.
Furthermore, while the scaled version of DC would not have the same mission length capability of its full sized variant, the 75 percent DC would have a comparable mission length to the currently in-use Soyuz spacecraft.
As proposed by the joint Vulcan Aerospace Corporation and Sierra Nevada Corporation joint mission document, pairing a scaled DC variant with the Stratolaunch system would enable “significant advantages … with regards to the variety of missions that can performed.”
Among these missions are LEO altitude observation flights, crew rescue and immediate cargo return flight from the ISS, and transportation to LEO destinations with day-of or long-duration runway landing return capability around the world.
As part of the variety of possible missions, the Stratolaunch-DC combination could be used for both crewed and uncrewed scientific missions based on medical, pharmaceutical, and material science.
The ability to fly both crewed and uncrewed scientific missions, according to the document, gives scientific researchers an “increased flexibility in when to launch, conduct and return their experiments,” with the added benefit of the customer being able to determine the landing location and return site of their scientific payload.
The document goes on to state that “customers with missions for Earth and space observation across the electromagnetic spectrum benefit from the rapid on-orbit and Earth return capability enabled by defined interfaces of an existing reusable platform landing on a convenient runway.”
That coupled with the low-g return environment by DC of high-value payloads that can then be quickly inspected, evaluated, refurbished, and then prepped for re-flight, offering a unique and thus far unachieved market in spaceflight operations and research.
Another proposed use of the Stratolaunch-DC vehicle would be to provide two crewmembers for LEO servicing and repair missions.
According to the study document, these missions would include the repair of satellites, support of assembly of commercial space stations and/or deep space exploration vehicles, as well as assistance with repairs to the ISS.
Under this type of mission scenario, Vulcan Aerospace Corporation and Sierra Nevada Corporation note that the air launch platform would provide “a broader range of the launch azimuths and orbit inclinations than conventional launch range locations.”
Crew and Cargo transportation to and from ISS:
This understanding of the broader range of the launch azimuths and orbit inclination opportunities directly relates to what both companies bill as one of the potential primary uses of the Stratolaunch-DC vehicle: emergency or rapid-response flights to ISS for crew and cargo needs.
Denoting the potential cost effectiveness toward a flexible and rapid approach for “bringing a small crew complement and limited cargo responsively to and from the ISS,” the Stratolaunch-DC vehicle would provide numerous launch opportunities to ISS that do not currently exist from the two active United States ISS launch centers.
Launches to the ISS from the Kennedy Space Center and Cape Canaveral Air Force Station in Florida mandate that launch vehicles move in a North-Easterly direction during ascent.
The location of the Kennedy Space Center and Cape Canaveral Air Force Station limits the number of potential launches to the ISS per day from these locations to just one – when the ISS moves in a North-Easterly trajectory on an ascending node portion of its orbit in relation to the launch location.
South-Easterly launches to the ISS from the Kennedy Space Center and Cape Canaveral Air Force Station are prohibited due to over flight restrictions on launch vehicles over the island nation of The Bahamas in the western Atlantic.
Likewise, missions to the ISS from the Wallops Test Flight Facility in Virginia are limited to South-Easterly trajectory launches due to overflight restrictions of the crowded northeastern states of the U.S. and the Maritime Provinces in Canada.
These types of restrictions would be mostly eliminated by the Stratolaunch-DC architecture.
Enabled by its 1,000 nautical mile outbound range to a desired launch location, the Stratolaunch-DC flight architecture would enable both North-Easterly and South-Easterly launch opportunities to the ISS daily or twice daily, depending on need, from the Kennedy Space Center and Cape Canaveral Air Force Station locations.
Furthermore, the ability to move the launch location in a 1,000 nautical mile direction from the takeoff runway would enable DC to achieve and maintain an annual 92 percent FD1 rendezvous launch opportunity to the ISS.
Moreover, under the proposed mission scenario of a rapid crew rescue mission to ISS, DC would not only be able to rendezvous with ISS on FD1 but also return to a landing facility in the CONUS within 24 hours of the launch.
Every orbit landing capability:
One of the other potential major advantages to a scaled version of DC in the Stratolaunch architecture would be its ability to land during every single orbit of its mission.
Owing to the use of nontoxic internal propellants for its maneuvering systems on orbit, DC, unlike the Space Shuttle fleet, would not contain any toxic vapors that would vent from the vehicle following landing.
This would enable DC to land on any commercial runway longer than 8,000 feet during any orbit of its mission.
This capability would also enable Dream Chaser to perform a variety of sub orbital missions that could serve as “Pathfinders for suborbital transportation in microgravity research” flights.
The joint presentation from Vulcan Aerospace Corporation and Sierra Nevada Corporation states that “such demonstrations could be performed with minimal additional cost or development effort beyond that already planned.”
Nevertheless, regardless of whether or not this version of DC actually comes to fruition, the continued aspirations of the Sierra Nevada Corporation strikes at the very nature of the emergent commercial spaceflight industry.
Studying the potential benefits and effects of new aerospace technologies, regardless of whether or not they are realized, enables an examination of the kind of progress we are capable of making versus the kind of progress we actually wish to achieve.
Evaluating a range of options paves the way, however slightly, for increased capabilities and refinement of procedures and operations for future space and endeavors to LEO, near earth objects, and eventually another planet.
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