Question: In mid flight during the drop test, the DC seemed to wobble from left to right. Was this normal? Answer: Great question! That 'wobbling' was actually an intentional 'Programmed Test Input', or PTI. This set of maneuvers was designed to assess the responsiveness and stability of the vehicle and provide us better aerodynamic data. Worked Great!!
Dream Chaser® spacecraft Free-Flight test by the numbers...
Quote from: yg1968 on 11/14/2017 11:45 pmQuestion: In mid flight during the drop test, the DC seemed to wobble from left to right. Was this normal? Answer: Great question! That 'wobbling' was actually an intentional 'Programmed Test Input', or PTI. This set of maneuvers was designed to assess the responsiveness and stability of the vehicle and provide us better aerodynamic data. Worked Great!! I noticed this wobble in the video, and was about to post about it in concern before I saw this post. I recall the lifting bodies tested in the '60s tended to have a roll instability, which at times caused loss of vehicles. I believe a large central vertical stabilizer was added to the HL-10 at one point, to try and reduce this instability.Good to see that the DC design not only anticipated this instability as a potential problem (which has obviously been designed out), but also that they incorporated an intentional roll instability in this ALT in order to see how well the avionics damped it out.Great to see!
Quote from: the_other_Doug on 11/15/2017 05:34 pmQuote from: yg1968 on 11/14/2017 11:45 pmQuestion: In mid flight during the drop test, the DC seemed to wobble from left to right. Was this normal? Answer: Great question! That 'wobbling' was actually an intentional 'Programmed Test Input', or PTI. This set of maneuvers was designed to assess the responsiveness and stability of the vehicle and provide us better aerodynamic data. Worked Great!! I noticed this wobble in the video, and was about to post about it in concern before I saw this post. I recall the lifting bodies tested in the '60s tended to have a roll instability, which at times caused loss of vehicles. I believe a large central vertical stabilizer was added to the HL-10 at one point, to try and reduce this instability.Good to see that the DC design not only anticipated this instability as a potential problem (which has obviously been designed out), but also that they incorporated an intentional roll instability in this ALT in order to see how well the avionics damped it out.Great to see!I believe it was the M2 F2. It was susceptible to a phenomenon similar to a Dutch role at high angles of attack. This led to an incident stemming from a temporary distraction from a helicopter that led to a late/overly aggressive pull-up which ended up producing the high angle of attack with the incident of instability. This instability was quickly recovered from but resulted in a late landing gear deployment. The landing gear was not fully deployed at touchdown and folded back into the aircraft. As the M2 F2 did not have either wings nor a relatively flat bottom the resulting lack of deployed landing ended up in a rather spectacular series of ground loops. With the last ground loop plopping the M2 F2 onto its back. (This spectacular footage was used in the opening clips of the $6 million man). The pilot suffered significant but not fatal injuries. The injuries were not fatal because the cockpit stayed in essentially one piece. Due to a design flaw in the original construction, the correction resulted in the cockpit being way overbuild to the original design specifications which would've been inadequate to save the pilot in this event. Eventually, the program continued with a new lifting body design called the M2 F3 that had a 3rd center fin to correct the instability problem.`
Here is a brief overview of several tests that have been completed to date on the Dream Chaser at NASA’s AFRC:Tow TestingThe Dream Chaser must undergo several tow tests to validate the performance of the spacecraft’s nose skid, brakes, tires and critical elements of the Guidance, Navigation and Control system of the Dream Chaser. During these tow tests, the vehicle is towed by a pickup truck to various speeds. Once the top speed is reached, Dream Chaser is then released from the tow hitch and the vehicle’s braking system is then used to bring it to a complete stop. Include link to new tow test video? 20/30/40 mph Tow Tests: March 15 and May 2, 2017 These tests were performed as part of a ramp-up approach to higher speed tow tests. Objectives included: Verify ground navigation, verify control, verify differential braking capability, verify simultaneous braking capability and verify tire/rolling friction models. 60 mph Tow tests: May 20, 2017 These tests were performed as part of a ramp-up approach to the Captive Carry and Free Flight tests later this year. After three successful tow tests at this speed, the avionics and brakes operated as expected and the vehicle is ready for the Free Flight later this year. One final 60 mph tow test will be completed before the Free Flight Test.Moments of Inertia (MOI) Tests: March 22 to April 1, 2017SNC partnered with the Flight Loads Laboratory at NASA’s Armstrong Flight Research Center to perform mass properties measurement testing on the Dream Chaser. The vehicle mass properties were successfully characterized allowing the team to better estimate the flight performance. Testing the vehicle in multiple configurations over multiple test runs reduced the testing uncertainty and provided accurate results.Airborne - Ground Resonance Test: April 24-26 2017SNC, again partnering with the AFRC Flight Loads Lab, measured the structural response of the Dream Chaser spacecraft to programmed flight control system sweeps at various frequencies. This test was performed with the Dream Chaser in an airborne configuration (landing gear retracted) and resting on the Flight Loads Lab "soft support" system to simulate an airborne environment. This test was the sister to the Rollout - Ground Resonance Test performed in Louisville, Colorado in December 2016.Radar Altimeter Calibration: April 28-29, 2017These tests were completed in Hangar 4833 (the former Space Shuttle hangar used for Enterprise) at AFRC. This test involved two cranes lifting the test article at three different pitch angles and deploying the gear at the max crane height during each test case. The main objective of this test was to demonstrate the integrated functionality and performance of the radar altimeters with the landing gear stowed, during landing gear deployment, and after landing gear deployment. Additional objectives included demonstrating that the radar altimeters worked simultaneously as well as independently.Ground and Airborne - Gain Margin Tests (GMT): May 15 and May 22-24, respectivelyOur Guidance, Navigation and Control System engineers designed specific software filters to ensure the Dream Chaser structure responds well to flight control surface inputs. Gain Margin Tests were performed in both ground and airborne configurations to evaluate specific flight control surface inputs and verifying fundamental laws of aerodynamics. The airborne gain margin tests were performed on the flight loads lab and ground testing was performed while Dream Chaser was on its landing gear.Additionally, the team just completed their first Captive Carry Test, allowing them to refine helicopter crew techniques, gather a wide variety of additional data on the vehicle and provide an opportunity for the flight control team to train prior to the Free Flight Test.https://www.sncorp.com/blog/snc-dream-chaser-armstrong-test-overview/
The 3G30C-Advanced solar cells will be manufactured at AZUR SPACE’s state-of-the-art manufacturing facilities located in Heilbronn, Germany. For AZUR SPACE, the Space Equipment business of Airbus Defence and Space will produce the completed solar panels in Ottobrunn, Germany, using decades of product heritage, engineering expertise and manufacturing experience.
The contract for work was signed with Sierra Nevada Corporation (SNC), and includes the main and nose landing gear as well as integrated actuation solutions for the landing gear and gear door systems manufactured at Triumph’s Redmond, Washington site.
Milestone 4B validated the spacecraft’s design for a safe and reliable return of cargo services to Earth through a gentle runway landing, signaling the program is one step closer to orbital operations. [...] The NASA Commercial Crew Program reviewed the data, confirming it fully met or exceeded all requirements and authorized full payment of the milestone. Additionally, SNC collected a significant amount of additional information that will be used for the final vehicle design. [...]The approach and landing test included intentional maneuvers both to assess the responsiveness of the Dream Chaser to control inputs and to measure the resulting stability of the vehicle under very dynamic, stressful conditions. This showcased the aerodynamic capability of the Dream Chaser as well as performance of the integrated computer system that autonomously returned the vehicle to a safe runway landing. These are critical components for orbital missions to and from the International Space Station.
Sierra Nevada Corporation’s Dream Chaser spacecraft passes major NASA milestone after free-flight test:https://www.sncorp.com/press-releases/snc-dream-chaser-passes-milestone-4b/
The vehicle’s next milestone will be the CRS2 Dream Chaser Critical Design Review, scheduled for 2018.
So in summary.They got the milestone payment from NASA for this.They have contracts in for solar panels to extend their duration on orbit (potentially allowing them to serve as a free flying laboratory)They have contracts in to a landing gear supplier to ensure that's taken care of, which is pretty important given the trouble their first landing test had with landing gear re-purposed from an old plane (although a perfectly reasonable strategy to keep down costs for an experimental vehicle)They are still in the running for NASA CRS contracts.Which all together is pretty exciting. 2018 should be quite a years for SNC and DC.