Author Topic: Sierra Space Dream Chaser UPDATE Thread (was SNC)  (Read 740660 times)

Offline the_other_Doug

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Re: SNC Dream Chaser UPDATE Thread
« Reply #800 on: 11/15/2017 05:34 pm »
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!!

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!
-Doug  (With my shield, not yet upon it)

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Re: SNC Dream Chaser UPDATE Thread
« Reply #801 on: 11/15/2017 09:44 pm »

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Re: SNC Dream Chaser UPDATE Thread
« Reply #803 on: 11/15/2017 10:50 pm »
Quote
Dream Chaser® spacecraft Free-Flight test by the numbers...

https://twitter.com/sierranevcorp/status/930944414452781057

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Re: SNC Dream Chaser UPDATE Thread
« Reply #804 on: 11/16/2017 12:20 am »
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!!

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.`

Offline Rocket Science

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Re: SNC Dream Chaser UPDATE Thread
« Reply #805 on: 11/16/2017 01:54 am »
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!!

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.`
Aren't we being naughty discussing in the update thread? To cap it off the M2 series was the inverted "half-cone" and the most radical of the lifting bodies. The X-24A/B (flat bottom) and HL-10 (cambered bottom) were more benign in handling especially after the glove was fitted to the HL-10 two outer vertical stabilizers... It was these two that led there design evolution to the X-38 and HL-20... The BOR-4/SPIRAL were not a true lifting body designs from entry to landing as their vertical stabilizers folded down to a conventional wing position in order to land. The HL-20 and Dream Chaser proved that the pure lifting body concept was sound aerodynamically subsonically to touchdown as we saw...
« Last Edit: 11/16/2017 01:58 am by Rocket Science »
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Offline Lar

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Re: SNC Dream Chaser UPDATE Thread
« Reply #806 on: 11/16/2017 02:31 am »
Yeah guys, there IS a discussion thread.
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Offline pargoo

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Re: SNC Dream Chaser UPDATE Thread
« Reply #807 on: 11/16/2017 06:06 am »
    Hopefully we'll get those approach/touchdown pics in hi-res sometime soon..?

Offline adrianwyard

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Re: SNC Dream Chaser UPDATE Thread
« Reply #808 on: 11/16/2017 01:16 pm »

Offline pargoo

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Re: SNC Dream Chaser UPDATE Thread
« Reply #809 on: 11/16/2017 08:47 pm »
     Well found :)

Offline rayleighscatter

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Re: SNC Dream Chaser UPDATE Thread
« Reply #810 on: 11/18/2017 02:41 pm »
An SNC Update that slipped under the radar (which is why it refers to a free flight test later in the year).

Quote
Here is a brief overview of several tests that have been completed to date on the Dream Chaser at NASA’s AFRC:

Tow Testing

The 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, 2017


SNC 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 2017

SNC, 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, 2017

These 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, respectively

Our 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/

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Re: SNC Dream Chaser UPDATE Thread
« Reply #811 on: 11/24/2017 06:51 pm »
FEATURE ARTICLE: Dream Chaser through critical landing test, prepares for orbital flights - https://www.nasaspaceflight.com/2017/11/dream-chaser-test-prepares-orbital-flights/

By Chris Gebhardt

Epic Uncrewed Dream Chaser L2 Renders - including the lead render - via NSF's Nathan Koga
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Offline yg1968

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Re: SNC Dream Chaser UPDATE Thread
« Reply #812 on: 12/01/2017 11:15 pm »
New video (highlights of the drop test) has just been released by SNC:
https://twitter.com/SierraNevCorp/status/936384381765201920

« Last Edit: 12/01/2017 11:17 pm by yg1968 »

Offline Yeknom-Ecaps

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Re: SNC Dream Chaser UPDATE Thread
« Reply #813 on: 12/09/2017 11:58 pm »
What was the date of the August tow test - 8/17 or 8/18?

per SNC media photo page - there are a number of pics of Dream Chaser including one that shows it braking on a taxiway with a date of 8/17 ..... https://www.sncorp.com/news-resources/media-resources/

while the SNC Twitter posts are on 8/18 ..... https://twitter.com/sierranevcorp/status/898666097313849344

which is the correct date?

Thanks.

Offline yg1968

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Re: SNC Dream Chaser UPDATE Thread
« Reply #814 on: 12/17/2017 04:54 pm »
AZUR SPACE Selected by Sierra Nevada Corporation to Build DREAM CHASER Spacecraft Solar Panels

http://www.digitaljournal.com/pr/3591087

The solar panels are on the cargo module that is attached to DC.

Quote
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.
« Last Edit: 01/02/2018 09:22 pm by yg1968 »

Offline yg1968

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Re: SNC Dream Chaser UPDATE Thread
« Reply #815 on: 01/02/2018 09:19 pm »
Triumph Expands Space Applications with Contract for Dream Chaser Spacecraft Landing Gear System:

https://www.businesswire.com/news/home/20180102005862/en/Triumph-Expands-Space-Applications-Contract-Dream-Chaser/

Quote
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.
« Last Edit: 01/02/2018 09:48 pm by yg1968 »

Offline yg1968

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Re: SNC Dream Chaser UPDATE Thread
« Reply #816 on: 01/05/2018 04:51 pm »
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/

Quote from: SNC
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.
« Last Edit: 01/05/2018 04:57 pm by yg1968 »

Offline deruch

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Re: SNC Dream Chaser UPDATE Thread
« Reply #817 on: 01/06/2018 01:41 am »
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 press release also included the following:
Quote from: SNC
The vehicle’s next milestone will be the CRS2 Dream Chaser Critical Design Review, scheduled for 2018.
« Last Edit: 01/06/2018 01:42 am by deruch »
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Offline john smith 19

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Re: SNC Dream Chaser UPDATE Thread
« Reply #818 on: 01/09/2018 02:53 pm »
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.
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Offline Rocket Science

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Re: SNC Dream Chaser UPDATE Thread
« Reply #819 on: 01/09/2018 03:36 pm »
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.
Just to jog you memory John, the F-5 landing gear was an artifact of what NASA selected for the HL-20 test vehicle and just a continuation thereof... The orbital will use a new system.
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