With Sierra Nevada Corporation’s Dream Chaser spaceplane through a successful and critical Approach and Landing Test milestone, the company is now shifting gears to focus on the all-important first orbital flight of Dream Chaser No Earlier Than 2020. That orbital flight will be part of Sierra Nevada Corporation’s fulfillment of NASA’s CRS2 Commercial Resupply Services cargo transportation effort for the International Space Station.
Approach and Landing Test paves the way for orbital flight:
Dream Chaser’s second Approach and Landing Test (ALT-2) was a resounding success, with Sierra Nevada Corporation (SNC) noting that all flight objectives were achieved and data points obtained – including some regarding the Thermal Protection System and flight avionics software that flew for the first time on the second ATL flight.
During a post-ALT-2 press conference, Steve Lindsey, Vice President of Space Exploration for SNC, provided an overview of the changes made to the Engineering Test Article (ETA) Dream Chaser between its first ALT in 2013 and its second in November 2017.
According to Mr. Lindsey, “We took steps to put in orbital vehicle development and build processes and really ramp up the impact of our processes. But we also wanted to put specific orbital vehicle equipment on this [ETA] to get certification requirements from this and really determine how it will fly back from space.”
This drive led to the inclusion of actual flight software that will fly on the orbital version of Dream Chaser as well as redundant sets of flight computers and navigation sensors, all of which Mr. Lindsey noted will fly on the actual Dream Chaser space vehicle.
“We upgraded with all of those systems; we put additional redundancy on the vehicle to make it more robust,” stated Mr. Lindsey.
For ALT-2, the boom was removed and replaced with a Flush Air Data System (FADS) that will fly on the orbital vehicle.
FADS uses a series of pressure ports on the nose of Dream Chaser to collect aerodynamic and angle of attack information that then feeds into the software and flight algorithms for control and stability during flight.
Inclusion of FADS on ALT-2 allowed SNC to gain critical data on how the system will perform during flight – something that will greatly aid the company as it pushes forward with finalization of all Dream Chaser system designs for flight.
Moreover, a slightly less obvious visual change was on the landing skid at the forward underside of Dream Chaser.
Unlike ALT-1, the second test afforded the opportunity to adhere actual Thermal Protection System (TPS) tiles that will fly on Dream Chaser to test those tiles’ ability to handle the skid landing system and assess how the tiles react once the skid hits a concrete runway surface.
“We actually flew real Thermal Protection System tiles … to test the manufacturing installation process and to characterize what would happen with a thermal protection system when we landed on a runway,” noted Mr. Lindsey.
“It gave us a chance to manufacture actual flight tiles and install those tiles and secure them onto are nose skid, and we were able to test what happened to those tiles when that skid contacted the runway.
“Because the tiles are fragile and have a low shear force, we wanted to characterize it and how it would affect our landing performance. And we were able to get all those objectives.”
Mr. Lindsey noted several times during the press conference that information was still being delivered and reviewed from ALT-2 and that some of the information was not available to discuss publicly at this point.
However, he did note that all test objectives appear to have been met successfully, with the 14,000 lbs Dream Chaser ETA gliding to its targeted point on runway 22L at Edwards Air Force Base, California, after a 60 second free flight that saw the vehicle achieve an angle of attack of 16.5 degrees and a nominal touchdown speed of 191 miles per hour (170 knots).
Once Dream Chaser touched down, the vehicle rolled out for 4,200 feet before coming to a stop, which SNC noted was slightly less than what they anticipate the heavier, operational Dream Chasers will achieve when they land at the Shuttle Landing Facility (SLF) at the Kennedy Space Center and the end of their missions
“We were a little limited on our test vehicle’s weight because of the helicopter,” noted Mark Sirangelo, corporate Vice President of SNC’s Space Systems. “The orbital vehicle will likely roll out a little bit further than that as it’s going to be a little heavier than our test vehicle.”
With the SLF at KSC being 15,000 feet long, a great deal of margin exists for landing operations of Dream Chaser at the Spaceport in Florida.
Onward to the orbital version for NASA’s CRS2 contract:
During the press conference, Mr. Lindsey noted that Dream Chaser passed its Preliminary Design Review (PDR) earlier this year with a 100% score, meaning there were no elements that would impede SNC’s ability to fly the vehicle as part of the CRS2 (Commercial Resupply Services 2) contract for NASA.
With those flights scheduled to begin No Earlier Than (NET) 2020, there is still a great deal of work for SNC with Dream Chaser, notably the CDR – Critical Design Review – coming up in 2018.
However, unlike a traditional CDR, which is when actual production would being, SNC is already well into the build for various elements of the first orbital Dream Chaser.
“With a traditional CDR, the intent is to stop the design and start production; however, CDR is not something in our world that happens all at one time. It’s a progressive CDR with multiple subsystems being worked on,” noted Mr. Sirangelo.
Mr. Lindsey added, “My experience in going all the way to a CDR and then starting to build is that that never happens. You always start building your critical path components to the best of your ability before you get to CDR because under a traditional program, your schedule is so long that it’s really not possible to do.
“So we use a concurrent engineering approach, and we get the critical path items and make sure we know what our long leads are. We have to go over those first.”
This means that several critical elements on both hardware and software side that will fly on the first orbital Dream Chaser are already well into production despite the CDR still being several months away.
“From a CDR standpoint, we start at the component-level – which we’ve been doing for quite a while now – and then we go to subsystem level CDRs and then build the system level CDRs and then finally we have the whole system itself,” noted Mr. Lindsey.
“So that’s the path we’re taking and the path that most people take. And it allows us to move out and make sure we keep an eye on critical path items so we can meet our commitments.”
In fact, the structural frame for the first operational Dream Chaser has been under construction at NASA’s Michoud Assembly Facility in Louisiana for some time.
But while progress is being made every day on this flight article and its systems, there are still a great many needs to meet prior to its first launch, including a large amount of testing before and after the vehicle is integrated as well as a large number of tests, trainings, and orientations for the vehicle’s ground and processing crews.
“There’s a huge amount of testing that has to take place before we get to orbit,” said Mr. Lindsey. “We test starting at the component level to the subsystem level to the system level and then finally to the integrated system level. And we do as much at the lowest level as possible first. And what we really focus on is ‘test like you fly’. We want to test it like we fly it.”
Since the ultimate test of Dream Chaser’s ability to fly will be its actual first flight, this “test like you fly” approach requires the utilization of numerous NASA centers – fully utilizing the partnership between SNC and the U.S. Federal space agency.
“We obviously can’t test it in orbit until we’re there, but we’ll build up a bunch of tests. One of the tests once we have the vehicle built is with a vacuum chamber facility where we’ll test it just like it’s in space in various thermal conditions and in a vacuum environment and bring up all of our systems.”
“We’ll take the orbital vehicle out to the Kennedy Space Center and do testing just like we did with the ETA out at Edwards, and we’ll do integrated testing with our launch vehicle, with our mission control center that we’re building, with all of our ground systems, and we’ll go through an extensive workup,” noted Mr. Sirangelo.
Just like they did at Edwards, a new set of people and a new team at Kennedy will have to be trained on how to work with the vehicle, with SNC noting that all of the lessons they just learned at Edwards will be transferred to Kennedy.
Once on orbit, Dream Chaser’s systems and rendezvous ability with the Space Station will be tested to ensure the craft can perform as designed before it approaches the Station for its first docking.
For the CRS2 contract, SNC plans to build two cargo Dream Chasers to fulfil its contractual obligations with NASA and the ISS.
At present, each Dream Chaser is designed for a minimum of 15 flights per vehicle, though the actual reuse number will not be known until the first few flights are complete and a good understanding of the vehicles’ performances and refurbishment needs are known.
Sierra Nevada hopes to be able to turn each Dream Chaser around within 60 days, and with two Dream Chasers fulfilling the CRS2 contract, the ability exists for the Dream Chasers to fly missions for other commercial customers in between their CRS runs to the Station.
(Images: NASA, Sierra Nevada, and L2 artist Nathan Koga – The full gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*)