At 1:52pm on Saturday, November 21st, Déjà Vu took to the Mojave skies, soaring beautifully from the launch rail to reach apogee at just over 25,000 feet. Déjà Vu was RPL’s first successful launch and recovery since Carbon Coby three years ago. Déjà Vu, however, is last year’s news.
Flash forward three months, and Déjà Vu II (also referred to as Déjà Two) is ready for launch, the second flight of the same vehicle. Same nosecone, same fins, same motor, and same enthusiasm and dedication from the team.
So if Déjà Vu worked so well the last time, why re-fly it? As the old adage goes, “if it ain’t broke, don’t fix it. Also, reusable carbon fiber motorcases are fly as hell. Pun intended” [Oprah, probably]. More importantly, Déjà Vu is a test bed for avionics and recovery, and was therefore designed to be reusable to allow multiple flight tests of the avionics and recovery systems. Flying the same rocket with new and improved systems is faster, more convenient, and allows us to focus our sights on other projects in the meantime.
After flying Déjà Vu once, several repairs and improvements were required to make Déjà Vu II flight worthy. First and foremost, a full HTPB R45 case repair was completed. The R45 is a rubber binder, and ensures the motorcase’s carbon was protected from the extremely hot combustion gases than can permeate through the rubber liner. The EPDM rubber liner itself was partially replaced in areas heavily seared by Déjà Vu I’s motor.
Secondly, a brand new nozzle was machined and inserted into the Déjà Vu motorcase. For its first flight, Déjà Vu’s nozzle exit plane was 1/8” inside the vehicle. As a result, the combustion gases directly impacted carbon fiber, baking out the carbon’s resin and degrading the carbon’s integrity. In anticipation of its second flight, Déjà Vu’s nozzle exit plane was extended 1/4” out of the vehicle to avoid baking out the aft end of the motorcase.
Of course, you can’t make any simple changes to rockets without affecting something else. Extending the motorcase changed Déjà Vu’s center of gravity, altering the vehicle’s entire flight profile. To account for the longer nozzle, 1.5 lbs of ballast were added to the nosecone to shift the center of gravity back to its original position.
Recovery was the biggest focus on Déjà Vu, given that this vehicle flight tests the recovery system that will be used on the next space shot. Like previous RPL vehicles, Déjà Vu I and Two both employed a drogue parachute (deployed at apogee) and main parachute (deployed closer to the ground). For Déjà Vu I, an e-match triggered the line cutters, which would cut two zip ties and release the main parachute far into its descent. Déjà Vu II released the main parachute using a "Tender Descender", which was rated for a much higher load than the line cutters, meaning it would be able to sustain much higher forces. The switch to a deployment bag occurred after doing some research and finding that many people have had more success with a deployment bag and tether release setup than with the burrito.
The final adjustment of note involved the prized custom-built avionics unit. For the first flight, the new High Altitude Module for Sensing, Telemetry, and Electronic Recovery (H.A.M.S.T.E.R) worked to perfection, tracking Déjà Vu’s position, velocity, and altitude throughout its flight. For the second flight of Déjà Vu, the avionics system was revised to include new sensors and a new physical layout. The new flight computer recorded data from a 9-degree-of-freedom absolute orientation sensor (giving live roll, pitch, and yaw values for the vehicle). This data, in addition to the previous version’s live GPS and barometric pressure readings, would allow for a complete reconstruction of the flight trajectory and attitude. Déjà Vu II was ready to take to the sky.
Everyone headed to Mojave, excited to see their efforts come to fruition - again! Even the head of the Astronautical Engineering department, Dr. Dan Erwin, decided to watch the launch. Preparations went as smoothly as we could hope for.
After months of hard work and analysis, Déjà Vu stood proudly again upon the launch rail, nosecone pointed toward the clear desert sky above the Mojave Test Area. As Arren made his way back into the bunker following the road and air safety check, RPL’s latest flight vehicle was one minute away from flight, and a million questions were flying through the minds of anxious Rocket Labbers. How would the carbon motorcase hold up? Was the R45 repair enough to prevent a mid-flight catastrophe? Was the ballast properly placed to ensure the correct flight profile? Only the ignition of Déjà Vu’s motor would shed answers to these questions.
At 12:30pm on Saturday, February 27th, Déjà Vu II blasted off from the desert floor with a powerful plume of dust and combustion gases, taking a straight trajectory into the Mojave sky. Cheers, hugs, high fives, and smiles were in order; all the repairs and improvements worked as expected, and Déjà Vu II made it two successful flights in a row for RPL.
Déjà Vu II reached apogee at 28,400 feet and a maximum speed of Mach 1.7, higher and faster than Déjà Vu I.
As anticipated, the avionics package transmitted live telemetry successfully during the entire flight, allowing Carter, Adam, and Jack to keep track of the vehicle in real-time. When it reached apogee, the notification was given that only the drogue had been deployed. However, the rocket started descending much slower than it should have, allowing us to extrapolate that the main parachute had managed to work its way out. Instantly the team started coming up with possible explanations, and ways to improve the system for future flights.
After the avionics team gave the location of the last coordinates of the rocket’s journey, some adventurous members of the team headed off into the wilderness in some off-roading friendly vehicles. Found in perfect condition, Déjà Vu was discovered northwest of the launch site near the intersection of Routes 44 and 83.
The story does not end here. Stay tuned for updates on our recovery system, H.A.M.S.T.E.R, and Fathom, our next flight vehicle. Of course, as always…