Sunday, March 10, 2019

Dawn of a New Era

The capability to once again send astronauts from U.S. based launch facilities to the ISS and beyond advanced to the next step on the early morning of March 2, 2019. SpX DM-1, a crew-capable SpaceX Dragon 2 vehicle launched atop a Falcon 9 from Kennedy Space Center's historic LC-39A, resulting in a successful Dragon 2 vehicle orbital insertion and Falcon 9 first stage landing.  The Dragon 2 performed a flawless set of ISS approach and maneuvering tests, resulting in docking to the forward port of the Harmony module just a little over a day later. This was the first time that a vehicle has docked to this port since July 10, 2011 when Atlantis docked during STS-135, the last flight of the space shuttle program. The Dragon 2 departed the station a few days later in the early morning of March 8 and subsequently landed in the Atlantic Ocean after a flawless re-entry and deployment of parachutes. The event was reminiscent of the Apollo program days, occurring just a few days shy of the 50th anniversary of the Apollo 9 CM splash down, the last vehicle to land in the Atlantic Ocean before SpX DM-1.

I decided to take another break from my ISS project early this year to concentrate on building a rendition of this historic spacecraft.  AXM had recently produced an excellent kit for the DM-1 mission and I decided that I would build and hopefully complete it in advance of the scheduled launch.

I started the build by extruding the main body parts and forming the various cylinders.  I used a broom pole to help me smoothly curve these sections.

The DM-1 design has the inter-stage section attached to stage 2.  I decided that I would attempt to build DM-1 in a fully detachable fashion including the second stage Merlin engine, so I separated the inter-stage and attached it to stage 1.  I printed sections from AXM's Bangabandhu kit for the inner section of the inter-stage, deployed grid fins, landing leg rods and inner faces of the landing legs and first stage.  I used a copy of the Crew Dragon heat shield to provide a top dome for the first stage LOX tank.  I affixed the inside inter-stage part from the Bangabandhu kit. Neodymium magnets were affixed to the inside of the inter-stage at the grid fin attachment points to accommodate easy swap of in-flight and landed grid fin variants.

I then turned my attention to the landing legs and hinges.  My goal for this section of the kit was to build the landing legs so that they can be positioned for both in-flight and landed configurations. I started by cutting out the parts for assembly of this section.

I assembled each leg, using the Bangabandhu kit inside leg parts to provide additional detail.  I placed magnets on the inside of each leg, along with corresponding magnets placed on the inner side of the first stage at the upper end of each leg attachment point.  I performed a test fit to verify correct magnet placement.

My initial plan for implementing the folded landing legs was to build the hinges, insert 22 gauge wire pins for each hinge, and use leg rods made of bamboo, with a hole drilled near the end of each using a hobby drill.

I test-fitted one leg using this design and quickly realized that minute differences in hinge angle and the tight tolerances between the hinge and rod cause binding issues that prevent the leg to swing freely.  After thinking about it a bit, I decided to try a "notched" hinge approach that uses a strap attach the rod to the hinge pin.  I created the notched rods first.

Next, I fabricated the hinges and base attachment points.  I used a drop of super glue at the ends of each hinge pin to firmly secure them. Leg rods were inserted into the ends of each leg.  I did not initially glue the rods into the ends of the legs, as to allow adjustments to deal with slight differences in the hinge angles.

I decided to use thin strips of heat shrink tubing for the hinge straps.  I attached each leg to its corresponding hinges by first gluing the hinge strap to the edge of each leg rod on the outside leg face with super glue.  I let the glue points thoroughly dry.  Next, I threaded the straps through the hinges and adjusted the length and orientation of each leg rod to optimize the travel for each leg.  Once a leg was properly positioned I glued the other end of each strap to the leg rod on the inside leg face.

Sections of bamboo rod were used for the leg struts.  I made each strut slightly longer than the length prescribed for each in the Bangabandhu kit.  I notched the ends to be smaller on each end of the struts to accommodate insertion within the mount points on the first stage and leg ends.

A test fit of the assembly verified that the design will hold the legs in their deployed configuration.

Next, I focused on the second stage.  I used parts from AXM's Falcon Heavy kit to build the Merlin vacuum engine and thrust structure.  I glued magnets within the stage attachment points between the inter-stage and second stage to provide a strong connection.  I also fabricated a shallow ring and attached it on the lower end of the second stage to provide additional rigidity for the inter-stage to second stage connection.

I chose to use aluminum foil for the outer cover of the thermal blanket surrounding the upper portion of the engine.

I fabricated a part for the upper end of the second stage LOX tank.

I then proceeded to build the in-flight and deployed grid fins.  I used watch washers glued to the backside of each fin to allow magnetic attachment for each.  Watch washers were affixed using super glue.

I attached the fins to see how they looked and also added some layering embellishments of umbilical attach points and gas vent ports.

I then tackled the first stage Merlin engines and octaweb configuration.  First, I extruded the parts and formed the bell housings for the 9 engines.

I cut short sections of toothpick to serve as as attachment points for the outer engines.  I made holes at each engine attach point and inserted the toothpick sections on the outer engines.  I glued the backside to affix the toothpicks, making sure that they sit against flush against the tabletop.

I affixed the outer engines to the toothpick nubs, making sure to align each engine bell so that the bell seam for each engine faces inward.  I placed a watch washer around the center engine attach point and also inserted a watch washer inside the bell of the center engine.  Another washer was affixed to the backside of the octaweb over the center engine hole.  These washers will serve as strengthening reinforcements for a metal rod that will be inserted up through the center engine for vertical display of the entire vehicle stack.

Another hole was placed through the bottom of the first stage disk and a washer was also placed around this hole for reinforcement.  A piece of close-cell foam was inserted into the lower section of the first stage and glued into the cylinder.  This foam will enforce stable vertical placement when the metal rod is inserted upward through the vehicle.

Next, I covered the bamboo struts with parts obtained from the Bangabandhu kit.  The lower section of the first stage was then again setup in "landed" configuration to verify fit and overall design.

I then moved on to building the Dragon vehicle.  I used v1 of AXMs design, which did not include the docking mode components.

First, I built the Dragon trunk.  I reverse-layered the umbilical connect point and placed magnets on the inside of the capsule attach points.  I then built the stability fins and attached them to the outside of the trunk.  As with the second stage, I fabricated a shallow ring and placed it on the inside bottom of the trunk to provide rigid connection to the upper portion of the second stage.

I concluded this section by attaching and forming the correct angle for the crew vehicle umbilical.

I then moved to building the crew vehicle.  I cut out the main section shell, removed the window areas, and extruded areas where the various thrusters reside.  I applied clear plastic to the backside of the part and reverse layered the thruster areas to provide depth/ realism.

I then built the nose cone, assembled the main body section, and affixed the nose cone.

Did I mention that I was building the crew vehicle while watching the DM-1 launch?  I had plenty of reference material to check against!

I then built and attached the SuperDraco thruster enclosures.

AXM released an updated version of the kit a few days later that provides the docking configuration components, so I decided to retrofit my build to accommodate the updates.  First, I had to cut off the nosecone.  I then cut out the docking ring and hatch parts.  I decided to cut out the hatch window.

The retrofit come out nicely...and I was able to get the nosecone to open/close by playing around a bit with placement of the hinge.  I ended up using a small piece of heat shrink tubing to facilitate repeated open/close of the nose cone.

I concluded assembly of this build by attaching the first stage upper and lower sections and attaching the raceways.  Here are a few shots of the completed build.