Orion Power Problems, Moon Flyby, Return Journey, & More
The Orion Spacecraft continues to make progress since it was sent into space on November 16th. The spacecraft has managed to stay very busy with different tests, burns, unique orbits, and now return trajectories. Not to mention some slight power complications that arose on December fourth.
Specifically, yesterday morning Orion completed one of its most important events yet with the near flyby of the Moon. Not only did this maneuver provide incredible images but it also provided the spacecraft with the final push necessary to send it on a trajectory for the Earth. At its current rate, in just 5 days on December 11th, Orion will splash down in the Pacific Ocean.
While the entire mission so far has been a major success, reentering Earth’s atmosphere is no easy feat. In this case, NASA will attempt the first ever skip entry for a human spacecraft – a maneuver designed to pinpoint its landing spot in the Pacific Ocean. However, if successful, we will be one step closer to launching humans on SLS with Artemis II. Here I will go more in-depth into the slight complications Orion ran into, yesterday’s flyby burn, the long awaited upcoming re-entry, and more.
Complications & Flyby Burn
Two days ago on the fourth NASA tweeted saying, “We’re approaching the Moon in preparation for our powered flyby on Dec. 5. During this maneuver Orion will fly as close as 79 miles / 127 km above the lunar surface.” In this case, Orion performed the second return trajectory correction burn on Sunday, Dec. 4, at 10:43 a.m. CST, using the auxiliary thrusters and increasing the spacecraft’s velocity by 1.16 mph (1.71 feet per second).
However, shortly after acquiring signal with the Deep Space Network’s ground station at 12:41 a.m. CST, Orion experienced an issue with a power conditioning distribution unit (PCDU), in which four of the latching current limiters responsible for downstream power were switched off. These lower-level switches connect to the propulsion and heater subsystems. Teams confirmed the system was healthy and successfully repowered the downstream components. NASA points out that there was no interruption of power to any critical systems, and there were no adverse effects to Orion’s navigation or communication systems. At the time, teams examined whether a potential contributor to this issue is related to a power configuration test implemented by the flight teams to investigate previous instances in which one of eight units opened without a command. The umbilical was successfully commanded closed each time and there was no loss of power flowing to avionics on the spacecraft.
Thankfully, just yesterday the agency tweeted mentioning, “On flight day 19 for our @NASA_Orion spacecraft, four limiters responsible for downstream power switched off due to an issue with a power conditioning distribution unit. The system is healthy, and there was no interruption to any critical systems.” This leads us to the flyby performed yesterday. Currently, NASA’s Orion spacecraft is on course for its return to Earth on Sunday, Dec. 11. The spacecraft made its second and final close approach to the Moon at 10:43 a.m. CST Monday, Dec. 5, just before its return powered flyby burn, passing 80.6 miles above the lunar surface. The burn, which used the spacecraft’s main engine on the European-built service module, lasted 3 minutes, 27 seconds, and changed the velocity of the spacecraft by about 655 mph (961 feet per second). It was the final major engine maneuver of the flight test.
Administrator Bill Nelson commented, “Orion is heading home! Today the team achieved another momentous accomplishment, flying Orion just 80 miles from the surface of the Moon. The lunar flyby enabled the spacecraft to harness the Moon’s gravity and slingshot it back toward Earth for splashdown. When Orion re-enters Earth’s atmosphere in just a few days, it will come back hotter and faster than ever before – the ultimate test before we put astronauts on board. Next up, re-entry!” Several hours before the lunar flyby, the spacecraft performed a trajectory correction burn at 4:43 a.m. CST using the reaction control system thrusters on the service module. The burn lasted 20.1 seconds and changed the velocity of the spacecraft by 1.39 mph (2.04 feet per second).
Skip Entry Technique
With Orion officially headed back toward Earth, NASA is very busy preparing for this important final milestone. Yesterday the mission management team convened and polled “go” to deploy recovery assets off the coast of California ahead of Orion’s splashdown on Dec. 11. As soon as Orion splashes down, a team of divers, engineers, and technicians will depart the ship on small boats and arrive at the capsule. Once there, they will secure it and prepare to tow it into the back of the ship, known as the well deck. The divers will attach a cable to pull the spacecraft into the ship, called the winch line, and up to four additional tending lines to attach points on the spacecraft. The winch will pull Orion into a specially designed cradle inside the ship’s well deck and the other lines will control the motion of the spacecraft. Once Orion is positioned above the cradle assembly, the well deck will be drained and Orion will be secured on the cradle.
Melissa Jones, landing and recovery director, at NASA’s Kennedy Space Center, highlighted that “Last week, we completed our final rehearsal with the USS Portland, which will be our recovery ship for Artemis I. We had a great three days working with them to refine our procedures and integrate our teams so we can meet the objectives of recovering the Orion spacecraft.” By now, Orion has used approximately 8,050 pounds of propellant during Artemis I, which is 180 pounds less than expected prelaunch. There are 2,075 pounds of margin available over what was planned for the mission, a 165-pound increase. As of 5:29 p.m. CST on Dec. 5, Orion was traveling 244,629 miles from Earth and 16,581 miles from the Moon, cruising at 668 mph.
As NASA continues to get ready for Orion’s splashdown, the Orion spacecraft is preparing for its biggest challenge yet. In reality, Orion is about to attempt the first skip entry for a human spacecraft – a maneuver designed to pinpoint its landing spot in the Pacific Ocean. During this skip entry, Orion will dip into the upper part of Earth’s atmosphere and use that atmosphere, along with the lift of the capsule, to skip back out of the atmosphere, then reenter for final descent under parachutes and splashdown. It’s a little like skipping a rock across the water in a river or lake. “The skip entry will help Orion land closer to the coast of the United States, where recovery crews will be waiting to bring the spacecraft back to land,” said Chris Madsen, Orion guidance, navigation and control subsystem manager. “When we fly crew in Orion beginning with Artemis II, landing accuracy will really help make sure we can retrieve the crew quickly and reduces the number of resources we will need to have stationed in the Pacific Ocean to assist in recovery.”
To put it in perspective, during Apollo, the spacecraft entered the Earth’s atmosphere directly and could then travel up to 1,725 miles beyond that location before splashing down. This limited range required U.S. Navy ships to be stationed in multiple, remote ocean locations. By using a skip entry, Orion can fly up to 5,524 miles (4,800 nautical miles) beyond the point of entry, allowing the spacecraft to touch down with more precision. The skip entry ultimately enables the spacecraft to accurately and consistently land at the same landing site regardless of when and where it comes back from the Moon. The skip entry also will allow astronauts to experience lower g-forces during Earth entry from Moon missions. Instead of a single event of high acceleration, there will be two events of a lower acceleration of about four g’s each. The skip entry will reduce the acceleration load for the astronauts so they have a safer, smoother ride.
Splitting up the acceleration events also splits up the heating, no small matter for a spacecraft that will endure approximately 5,000 degrees Fahrenheit upon reentry, half as hot as the surface of the Sun. The heat the spacecraft will experience upon reentry will be split over two events causing a lower heat rate at both occurrences and ultimately making it a safer ride for the astronauts. Yesterday’s maneuver set the spacecraft on its trajectory back toward Earth to enter our planet’s atmosphere traveling at 25,000 mph (11 kilometers per second), responsible for producing extremely high temperatures, faster and hotter than Orion experienced during its 2014 flight test. However, if everything goes according to plan, Orion will splash down approximately 50 miles (43 nautical miles) off the coast of San Diego, California, where rescue teams are close and can quickly recover the spacecraft. All of which will set the stage for Artemis and help prepare the agency for Artemis II and beyond.
Conclusion
NASA is only 5 days away from Orion’s expected splash down in the Pacific Ocean. So far the mission has been a major success with yesterday’s flyby burn setting Orion on its final trajectory. A lot of firsts are being made on this launch including the reentry maneuver hoping to improve future astronauts’ safety, speed, and more. We will have to wait and see how it progresses and the impact it has on the space industry.
