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Viking '75 Mars Lander Construction, Looking for Viking lander design/construction information
Tom Dahl
post Jun 6 2016, 11:48 PM
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On May 20 I visited the Smithsonian National Air and Space Museum in Washington DC to photograph the Viking lander Proof Test Capsule (PTC), which has recently been undergoing conservation prior to being re-exhibited in the remodeled Boeing Milestones of Flight Hall. Thanks to the very kind assistance of Matthew Shindell, curator in the space history department, and Jessica Bulger of the collections department, I had an hour of special access prior to museum opening. This allowed me to get over and under the lander for detail photography, and include scale references against some components. The result was nearly 900 images I've processed, added descriptions, and uploaded in a new public album.

This was the last time in probably quite a while that 360-degree access will be possible to the Viking PTC due to the new exhibit arrangement that will not allow the "back" (leg 1 area) to be readily seen. For the past few decades the PTC has been exhibited in a very professional glass-walled module, which allowed 360-degree views but mostly through one or two panes of brown-tinted glass. For a short period this spring, including the recent day I was photographing, the lander was removed from that module (which is not being re-used). Thus reflection- and smudge-free images were possible, and I took great advantage of the opportunity - hence the large size of my new album. (During three visits in 2011 and 2012 I acquired about 450 earlier images, some of which suffer from glass artifacts.) Most of the images were taken later on May 20 during normal operating hours, around and between the temporary barriers surrounding the lander. But the early-morning hour with the Smithsonian staff allowed unusual details to be captured, for which I am very grateful! It was a privilege to be granted such access. Thank you Matthew and Jessica.

On a related note my on-going project to create a high-fidelity digital 3D model of the Viking lander continues. I decided to try having a commercial 3D print made of some small parts, for fun. I had to choose something which I had already modeled (of course!), which had a minimum wall thickness large enough to be within the printing capability (which eliminates some parts, even at full scale), and which was not cost-prohibitively large. I chose to print one of the guide roller assemblies that interfaced between the lander and its Base Cover guide rails:
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The vendor I chose (partly based on materials and print technology availability) is i.materialize based in Belgium. As can be seen in the image there are three wheels, which spin nicely on their (separately printed) axles. The faceting visible in the curved rollers is how the digital model was designed, for simplicity. The axles have 0.02-in (wide and deep) grooves near their ends for retaining clips, which printed satisfactorily. The wheels and axles were printed in "prime gray" and the body was printed in "high detail resin".
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Tom Tamlyn
post Jun 7 2016, 05:53 AM
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QUOTE (Tom Dahl @ Jan 16 2016, 10:15 AM) *
I just completed a new video animation of my work-in-progress digital 3D SketchUp model of the Viking lander (which is freely available at the preceding link). This video is nearly six minutes long and shows detailed operation of the lander leg mechanisms, with cut-away sections revealing internal latches, springs, the honeycomb attenuator, pin-puller, etc.

I had assumed that your interesting project was to create a detailed 3D model of the external shape of the Viking lander. This animation includes some selected internal details. Was that a limited extravagance, or is it your goal ultimately to include all the internal mechanisms as well? Or perhaps you simply intend to pursue as much detail as you can find, whether internal or external.
QUOTE
Thanks to the very kind assistance of Matthew Shindell, curator in the space history department, and Jessica Bulger of the collections department, I had an hour of special access prior to museum opening. This allowed me to get over and under the lander for detail photography, and include scale references against some components.

Did this session satisfy all of your needs for examination of the Proof Test Capsule? Or is there ongoing tension between your interests and the Smithsonian's view of its mission and responsibilities?
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Tom Dahl
post Jun 7 2016, 11:42 PM
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My main goal is to model essentially all exterior piece-parts of lander hardware (though I'm undecided about a few external components such as the prominent wiring bundles - they would be hard to model and I don't have good data on the routing of the Flight lander wiring, which differs from the PTC and other test-unit wiring in various places). I would like to model the interior but I lack sufficient references to do a high-fidelity job on most items (and doing so would add about two years to the project). I'm doing selected "hidden" parts for which I have good information and which catch my eye, such as the leg mechanisms and the three interior struts that support the large Terminal Descent Landing Radar (TDLR) box below the lander body. I plan to model the Radioisotope Thermoelectric Generators (RTGs) to a good level of detail because they are such iconic devices and I have the info. I'm not sure about internals of the three Terminal Descent Engines (TDEs), I've got almost enough information on them.

In my fantasy I would also model the Aeroshell and its numerous components, and the Base Cover and Mortar Support Truss. But they would entail another couple years' work, so that's very uncertain.

Regarding my recent Viking research at the Smithsonian NASM, it was wonderful and a real privilege to be allowed a one-hour session right up against the lander with a collections specialist! To be clear I am not affiliated with any institutions, the staff did not know me, and I have no formal credentials. Thus being granted that access was an honor for which I am grateful. With that said there was a LOT of additional information I would have loved to acquire. Quite understandably (for the reasons above) I was not permitted to make contact with the lander myself. I did provide references to my earlier visits at NASA Langley, the Virginia Air and Space Center, the California Science Center, the Museum of Flight in Seattle, and the founders of the Viking Mars Missions Education and Preservation Project, who all allowed me to take direct careful measurements of authentic lander hardware. I could have spent ten hours gathering measurements and still not covered everything on my "PTC Bucket List." But I completely understand why that was not permitted.
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Tom Dahl
post Aug 7 2016, 01:18 PM
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I recently completed a 12-minute making-of video that illustrates some of the research methods and modeling approaches I've been taking during creation of the Viking lander digital model.

In July I was delighted to show and discuss the model at the 40th landing anniversary event organized by the Viking Mars Missions Education and Preservation Project, with a personal invitation by Rachel Tillman. The event was sponsored by Lockheed Martin and held at the Wings over the Rockies Air and Space Museum in Denver CO. The lander was built by Lockheed Martin heritage company Martin Marietta just outside Denver. I met a number of original Viking folks at the event, which was a treat!
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Tom Dahl
post Nov 22 2016, 01:11 AM
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This past weekend I completed a 3D digital model (using SketchUp) of the Viking lander's Surface Sampler Collector Head, a complicated electro-mechanical device. Here is an image comparing the model to an actual spare unit that I was able to examine at NASA Langley Research Center in 2014:
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The 3D model contains all major and many minor internal components which allow it to virtually "operate" as the real thing. Here is a cut-away showing the internal sealed DC gear-motor (in gray), the motor-housing/gimbal structure (partly in green, to signify a somewhat approximated design due to lack of references), the solenoid (behind the lid), and the ring magnet arrays in the backhoe:
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Here is an exploded view of the parts:
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The model has been uploaded to the SketchUp 3D Warehouse. My thanks to the Viking Mars Missions Education and Preservation Project for providing some valuable collector head internal design documentation from Martin Marietta.
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Tom Dahl
post Dec 24 2016, 04:30 PM
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I've completed modeling the hardware that mounts the Surface Sampler Collector Head to the sampler boom or arm. Here are some renderings of the model:
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rlorenz
post Dec 25 2016, 03:58 PM
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QUOTE (Tom Dahl @ Dec 24 2016, 11:30 AM) *
I've completed modeling the hardware that mounts the Surface Sampler Collector Head to the sampler boom or arm. Here are some renderings of the model:


Amazing achievement, Tom. Keep posting about this great project..
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Tom Dahl
post Mar 28 2017, 02:53 PM
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Making progress on the Surface Sampler Acquisition Assembly (SSAA) housing, from which the furlable boom (with collector head mounted at tip) extends and retracts. Here are the eight frames comprising the housing's structure. The numerous skin panels which are bonded or screwed to the frames are not yet modeled.
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djellison
post Mar 28 2017, 03:44 PM
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As someone who has dabbled in various 3D platforms for some time - including SketchUp - I genuinely doff my cap to you - this is incredible work, Tom.

Have you considered using Structure from Motion (i.e. ingesting a LOT of photos into something like AgiSoft Photoscan) - as way of getting reference photos into a 3d digital domain? Happy to help with that if it could be useful.
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Tom Dahl
post Mar 29 2017, 11:24 PM
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Thank you for the compliment, Doug! It's a labor of love, equal emphasis on labor and love. smile.gif I've probably invested about 1500 hours in front of SketchUp and Photoshop working on the lander model. The whole thing is available to anyone free of charge on my DropBox site; I'm sure I posted a link earlier in this thread.

Regarding automated processing of 2D photographs into a 3D image, I have in fact experimented briefly with AgiSoft's Photoscan. Last summer Mattias Malmer and I corresponded about our respective spacecraft-modeling projects and he suggested it. I was totally disappointed with the result, though I acknowledge I gave it a challenging object to detect and model. I have 30 or so photos of a particular bracket on the lander (High Gain Antenna down-lock), which I fed to the software. The images were ~4300x2800 pixels and taken from viewing angles of about 180 degrees horizontally and perhaps 90 degrees vertically (range limited by obstructions). It never yielded anything more than a blob. I tried a few different crop levels, and even masking out the (complex) background. Nada. I suppose I should have tried on a simpler case, but I was suspicious of the level of dimensional accuracy that might result in the best of cases.

In total I have over 3500 photos I've taken of actual viking test hardware (all posted for free access in Google Photo albums), so I've got a reasonable collection of source images for experimentation. Maybe again at some point!
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djellison
post Mar 30 2017, 05:51 PM
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Yeah - structure from motion can struggle with flat mechanical parts - I tried a couple of years ago with the refurbished Ranger bus being worked at the California Science Center ( https://sketchfab.com/models/cae6c1b3d25349...59bc6af98f95e51 ) and the effort was barely worth it. I'd like to try with your photos - but the links to your albums earlier in this thread appear to have died.

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Tom Dahl
post Mar 30 2017, 11:31 PM
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Thanks for pointing out dead links. I have edited the base post to add a complete set of the on-line resources I've created, using the current Google Photos style links.

If you want to experiment with structure from motion, perhaps a good candidate would be the High Gain Antenna. There is an album of detail photos dedicated to the HGA. There are also a fair number of HGA photos in a few other albums: the Flight Capsule 3 at The Museum of Flight, the Proof Test Capsule and album 2 at the Smithsonian NASM, and the Science Test Lander at the Virginia Air and Space Center.
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Edited to add that I forgot to comment on the Ranger representation you shared. Fascinatingly uneven result, if I may say. Some of the small orange cables look very nice while seemingly-prominent structural elements are incomplete. I suppose a result of the particular image coverage used to perform the reconstruction?
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Tom Dahl
post May 20 2017, 03:54 PM
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During the past few weeks I've added the front inset bulkhead (through which the boom or arm protrudes) with nearby boom-retract limit microswitch, plus the exterior skin panels of the Surface Sampler Acquisition Assembly (SSAA) housing frames. The SSA looks a bit more complete at this point (even though it's empty). Also added are the pedestal base on which the SSAA sits and the yoke gimbal mount (more details in next reply).
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Tom Dahl
post May 20 2017, 03:59 PM
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Here are close-ups of the pedestal base and yoke gimbal mount, which includes the azimuth and elevation drive assemblies, for the Viking lander's surface sampler's housing. The gear train for the azimuth drive (horizontally-arranged gearing, on the left) is based on a drawing of the actual hardware though the tooth counts and dimensions are estimated. The vertically-oriented elevation drive has an approximately-correct fixed worm-wheel gear, but the spur and bevel gears inside the little gearbox are speculative due to lack of reference documentation. The gear tooth profiles are simplified. The large cylinder is a very rough model of the drive motor for the elevation axis.
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Tom Dahl
post Jun 27 2017, 12:01 AM
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Next up are the components of the boom extend-retract drive mechanism and the boom stowage drum for the lander's Surface Sampler Acquisition Assembly, in approximate form due to lack of detailed reference material (as denoted by the green tint). The hollow interior of the large drum contained a few feet of the Flat Conductor Cable (FCC) that runs through the middle of the boom (not shown here, but see earlier replies for renderings of it). This slack allows the boom to extend and retract by ten feet, as the slack within the drum is wound clockwise around the stationary hub when at one end of full travel, and re-wraps to be counter-clockwise around the hub by the time the other end of travel is reached. The flattened boom itself wraps around the exterior of the drum. The large slot in the drum (visible in the second image) allows the FCC to pass from the boom into the drum, and the slot in the hub (partly visible in the first image bracketed by curled bend-limiter fences) allows the FCC to exit the assembly through the center of the hub (coming out on the side visible in the third image).
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