Sierra Nevada Corporation (SNC) have provided a positive overview on their progress in readying their Dream Chaser spacecraft for commercial crew operations in 2016. A fan favorite – due to its baby shuttle orbiter appearance – Dream Chaser has been paired with the highly reliable Atlas V launch vehicle as part of their Commercial Crew Development (CCDev) aspirations.
SNC Chasing The Dream:
SNC class themselves as the complete system provider and claim to have demonstrated significant progress maturing design and development of the Dream Chaser Space System (DCSS), which saw them become one of the winners of the CCDev-2 contract award – resulting in $80m of funds being provided from NASA, who are aiming to return a domestic crew launch capability by the middle of the decade.
The Dream Chaser would launch atop of an Atlas V – building on studies which range back several years – as first revealed via NASASpaceflight.com’s article on the Memorandum of Understanding (MOU) with the United Launch Alliance (ULA) in 2007.
Dream Chaser – which is a reusable lifting body vehicle based on the form of NASA Langley’s HL-20 spaceplane concept from the 1980s – can land on a conventional runway, unlike all of its capsule-based competitors, as much as SpaceX are looking into a rocket assisted landing on land for their Dragon capsule.
Working through the completion of 19 milestones per CCDev-2 – the latter of which is listed as the Free Flight Test, which will be a piloted Flight test from carrier aircraft to characterize handling qualities and approach and landing – Senior Director of Space Exploration Systems, Merri J Sanchez, PHD, updated the status of their activities this week at the AIAA Rocky Mountain Section Speakers Program in Colorado.
Noting the extensive heritage Dream Chaser already has on record – which ranges as far back as the genesis of the Russian BOR-4, X-24A and HL-10 – Dr Sanchez cited a total of 1200 wind tunnel tests and numerous simulations gained via the HL-20 program alone.
Utilizing modern materials, CFD (Computational Fluid Dynamics) and their own wind tunnel data, the design continues to be qualified via advanced development techniques.
With the Outer Mould Line (OML) of the HL-20, Dr Sanchez noted Dream Chaser has low re-entry deceleration loads – less than 1.5G – with a large cross range ability, low impact landing and no black zones during ascent trajectory, with Return To Landing Site (RTLS) ability (runway return).
The vehicle is capable of flying with 2-7 crew in upright or recumbent seating, or uncrewed, with the ability of carrying 1000kg of cargo in replacement of crewmembers. The crew will ingress via overhead access hatch on the ground, while the spacecraft will dock aft facing.
Dream Chaser sports non-toxic hybrid motors (HTPB, N2O) which have been built in-house, with Reaction Control Systems (RCS) utilizing N2O and Ethanol. The spacecraft’s on orbit power will be supplied via Batteries using a trickle charge from the ISS.
SNC also cite they are working with a wide range of companies to achieve their orbital goals, mentioning ULA, USA, Aerojet, NASA, Scaled, MDA, Boeing, Hamilton Sundstrand, Draper Lab, SAS and others. They also have an active student program, who have assisted in model and simulation work.
Milestones included three rocket motor tests in one day including vacuum start, and CCDev testing will continue through to the end of July, 2012 – a process which ranges from physically building flight hardware, through to advancing through the PDR (Preliminary Design Review) level, and the testing of numbers systems through the CDR (Critical Design Review) phase.
SNC noted that the engineering test article – which is entirely made out of composite materials – was delivered in December of last year, which will become a flight vehicle for an atmospheric test flight.
Other items of interest were mentioned during the address, noting the first uncrewed launch will involve horizontal landing. The vehicle is capable of mission durations lasting a lengthy 210 days when docked (to the International Space Station), and will always be “crew active” for prox ops.
For abort safety, the vehicle does sport crew bailout capability – as a last resort, with runway landings always intended in abort situations – and for a pad abort, testing will use hybrid motors which are sized for specifically for such an emergency scenario.
The crew, which will launch and land in Florida – as much as it can land at any commercial airport – will egress out of the aft of the vehicle on the runway after landing.
Dream Chaser is targeting a landing speed of 191 knots, after re-entering the atmosphere protected by what is being described as a Thermal Protection System (TPS) that is similar to that on the Space Shuttle.
Dr Sanchez also recognized a certain romanticism between Dream Chaser and fans of the Shuttle, but noted their “runway landing” vehicle is very practical, particularly from a turnaround and cross-range perspective.
In fact, it was noted the vehicle has around one thousand miles of theoretical cross range, it can land on a runway from virtually any point in the orbit, and can land on a CONUS runway in no longer than six hours. It was also mentioned that Dream Chaser is capable of something the ISS program consider particularly valuable, which is its “dissimilar redundancy” when compared to capsules.
Looking towards the future, SNC expect the CCDev-3 stage to be announced as early as February 7, with a 45 day response period. SNC have seven more milestones to complete via the ongoing CCDev-2 stage.
Speaking about their launch vehicle of choice, SNC were full of praise for Atlas V and its reliability – something which has seen it become the main vehicle of preference with several of the commercial crew companies – despite Atlas V’s current status of not being a human-rated vehicle.
As confirmed in July of last year, NASA and the ULA are working via an agreement for technical support via NASA’s Commercial Crew Program focusing on the human rating of the Atlas V. The unfunded act is expected to result in certifying Atlas V to launch NASA astronauts riding in vehicles such as the Dream Chaser, Boeing CST-100 and Blue Origin’s spacecraft.
NASA is providing feedback to ULA based on its human spaceflight experience for advancing Crew Transportation System (CTS) capabilities and the draft human certification requirements. In turn, ULA is providing NASA feedback on those requirements, including providing input on the technical feasibility and cost effectiveness of NASA’s proposed certification approach.
ULA’s obligations include; continuing to advance the Atlas V CTS concept, including design maturation and analyses. Conduct ULA program reviews as planned, Perform a Design Equivalency Review (DER). Develop Hazard Analyses unique for human spaceflight. Develop a Probabilistic Risk Assessment (PRA). Document Atlas V CTS certification baseline, and Conduct Systems Requirements Review (SRR).
The company expect that hardware testing with the Atlas V – from an integration standpoint – will be the next major phase of marrying the two systems together, ahead of their combined launch into orbit in the coming years.
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