Dream Chaser Docking Procedures Are Being Tested In Prep For Launch
As Dream Chaser approaches its first launch, teams have been busy making sure the spaceplane is ready. This not only includes physical progress and development but practice and coordination with NASA surrounding the flight profile and ISS docking procedure in particular. On this first mission, Dream Chaser Tenacity will be carrying valuable cargo and will need to dock with the ISS before returning home.
This is a delicate process that can’t afford any mistakes for the safety of the vehicle and more importantly crews on the International Space Station. Over the past few days, Sierra Space has been going through different simulations for this exact process. This includes the approach starting over 100 km below the station all the way to the connection.
As of right now, Dream Chaser Tenacity is practically ready for flight. Based on reports from Sierra Space the test article is just about complete and could already be finishing its final testing. Here I will go more in-depth into this simulation, the final work on Tenacity, what to expect in the coming weeks, and more.
Dream Chaser Simulations
Yesterday, Sierra Space tweeted saying, “If we are to enter the next period of human innovation, precision is key. Our team recently completed a successful comprehensive rendezvous test with #NASA to simulate the docking procedures of our Dream Chaser® spaceplane.” Simulations are extremely important and only become more necessary when humans are involved. This practice could be the difference between a mission going perfectly or failing. When two spacecraft meet while in orbit, precision is key. The trajectory and timing need to be perfect, as do the complex mathematical calculations that determine the position and speed of both spacecraft. That’s why Sierra Space is practicing every part of the process.
Focusing on the recent simulation, the Joint Multi-Segment Training (JMST) was considered a success by both Sierra Space and NASA. The second JMST will be held on July 21. As far as what actually happens during these sims, the company first highlights the importance of dedicated roles. For example, the team of experts is led by an experienced Flight Director, similar to the setup at NASA’s Mission Control Center. This leader is responsible for overseeing the entire team of mission controllers, as well as all aspects of the mission from launch to landing.
During the simulation, the Flight Director maintains constant communication with their team and NASA, ensuring the spacecraft remains on course, as well as preparing for any changes or updates to the mission plan. In both simulations and real rendezvous berthing instances, the Flight Director is the direct line to mission control. Therefore, they’re heavily involved in every practice scenario and must be trained to make quick, informed decisions under high pressure. The rest of the simulation crew assists under the supervision of the Flight Director and helps them prepare for every possible mishap or complication.
The actual run initializes at 119 km below and behind the ISS. Through a carefully choreographed set of “burns,” the simulated Dream Chaser approaches and intercepts the earth radius vector directly below the ISS.
With built-in holds at several points along the way, Dream Chaser gradually climbs up to a capture point that is 11.5 meters below the space station’s Japanese Experiment Module. When Dream Chaser is at the capture point, the ISS crew moves the robot arm into position and grapples the spacecraft. The company was quoted saying, “This can take approximately six hours from start to finish in training simulations, and in most cases, is not problem-free. Every rendezvous simulation provides the opportunity to encounter and address potential problems for the Dream Chaser. Except for the launch and landing day, rendezvous day is considered a ‘dynamic’ operation – and safeguarding the astronauts aboard the ISS is of paramount concern” they said.
Sierra Space also pointed out that “The more space companies like ours can learn about potential risks via a simulation, the better we can protect real lives up in space someday. At the end of the day’s simulation, the team debriefs all that transpired, including what went well and the opportunities to learn and improve. Then, it’s back to the drawing board to prepare for the next simulation” they said. With less than 6 months until the scheduled launch, the company still has a lot of simulations left before they are ready.
Upcoming Launch
While the simulations provide great practice and experience to the crews responsible for controlling Dream Chaser, no matter how accurate they will still differ from the actual launch. Sierra Space highlights that “in real-life missions, things often fall behind – and even the slightest adjustment to timing during rendezvous can mean a world of difference. They continued by saying, “Although we cannot predict every outcome in space, we can do everything in our power to ensure that timelines and procedures are met with precision. A key part of simulations at Sierra Space is ensuring that the core events are never missed. Ultimately, the Sierra Space Flight Operations team throws various malfunctions and scenarios at the space crew and controllers to make them sharper. When unexpected (and expected) issues arise in space, everyone needs to be as prepared as possible to react and adjust” they said.
In regard to the most recent simulation starting around 119 km away from the station, teams primarily used the thrusters on Tenacity. Dream Chaser spaceplanes are equipped with 24 Reaction Control System or RCS thrusters across their entire body. The RCS will provide maneuvering capability to allow for the accurate docking of the Dream Chaser to destinations in low-Earth orbit. Specifically, a reaction control system is a spacecraft system that uses thrusters to provide attitude control and translation. Reaction control systems are capable of providing small amounts of thrust in any desired direction or combination of directions. These fine adjustments will be used throughout the majority of the docking sequence.
Looking at the full first mission launch profile gives us a better idea of the other big mission milestones and what Sierra Space still needs to practice. It will start with the launch of ULA’s Vulcan Centaur with Tenacity folded within the farings. Following liftoff, stage separation, and second-stage ignition, the spaceplane will separate from the second stage when it’s completed its burn. At this point, the Shooting Star service module will deploy its solar panels and Tenacity will extend its wings which were folded during launch to fit within the fairings. Not long after this point, Tenacity will be exactly where this simulation put it, around 119 km away from the station. For the next 10-plus hours, the spaceplane will get closer to the station and eventually berth to it.
The planned mission duration is 82 days which means Tenacity will stay docked at the station for a few months. During that time crews will have unloaded all the supplies on the spacecraft and even loaded the shooting star module with garbage and other disposables. Finally, after over two months attached to the station Dream Chaser will disconnect. It will make its way further from the station and prepare for reentry. Before this, the Shooting Star module will separate from the spaceplane and burn up upon reentry. If everything goes according to plan Tenacity will enter the Earth’s atmosphere and survive. It would then attempt a controlled runway landing and complete the first launch of this spacecraft.
With the flight profile and recent updates in mind, it brings up the question of when will this launch actually take place. Unfortunately, it’s hard to say with a lot of recent delays from various involved companies. For example, the most recent and official delay came a few months ago in March when NASA updated its internal schedule to show that Tenacity would berth to the International Space Station no earlier than December 17, 2023. However, new reports coming in show that the spaceplane is now targeting a launch in the first quarter of 2024.
In relation to this, Dream Chaser’s launch vehicle, ULA’s Vulcan, also just ran into some significant issues. The upper stage of the rocket needs to be shipped back to the factory. ULA hasn’t provided any launch date but the best case scenario is late this year however early next year is also a possibility. The main issue is that this maiden flight isn’t even with Tenacity, the spaceplane is meant to lift off on the second Vulcan launch. This means that ULA won’t be ready until the first mission is complete and then they can begin preparing the next Vulcan rocket. While there are other launch vehicles available that could carry Dream Chaser, ULA, and Sierra Space have a big contract. Back in 2019, it was announced that all six Dream Chaser CRS-2 flights would be carried into orbit by ULA’s Vulcan launch vehicle. In all likelihood, Sierra Space and Tenacity will wait for ULA to be ready.
Conclusion
Sierra Space just completed a full day of simulations related to Tenacity’s first flight and its approach to the ISS. This is an extremely precise process that cant afford any mistakes. We will have to wait and see how it progresses and the impact it has on the space industry.