Orion reaches the moon, hums to the surface, and prepares for orbit • The Register
NASA’s Orion spacecraft has arrived at the Moon and swung to the far side as it prepares to enter orbit around Earth’s largest satellite, which will take it farther from home than any (possibly) manned one spaceship in front of him.
Orion used its orbital maneuvering engine to accelerate around the moon for two and a half minutes to receive gravitational assist, which NASA described as an “outbound powered flyby burn.” This is the first of two maneuvers the capsule must perform to enter a distant retrograde orbit. or DRO.
Distant retrograde orbits are known to be incredibly stable for reasons similar to the Lagrange points that keep the James Webb Space Telescope in a reliable location: A gravitational balance between two large celestial bodies. In this case it is the earth and the moon.
DROs are retrograde in the direction in which the Moon moves around Earth and distant in the sense that Orion will end up flying more than 57,250 miles beyond the Moon at its most distant point in orbit – further than any space capsule in front of him.
A map of Artemis I’s trajectory using the DRO (in grey)
On Monday, November 28th, Orion will be at its furthest point – more than 268,500 miles when the spacecraft will reach its lunar furthest point this Friday.
While Orion conducts science experiments in the frigid niche of DRO space for six to 19 days, Orion will also give NASA the opportunity to test their systems for the Artemis II mission, which will see the manned spacecraft fly to the Moon and back in the May 2024 (for now).
“With no crew aboard the first mission, DRO allows Orion to spend more time in space on a rigorous mission to ensure spacecraft systems such as guidance, navigation, communications, power, thermal control and others are ready to protect astronauts on future crewed missions said Mike Sarafin, manager of the Artemis Mission.
Mixed news for Japan’s Artemis payloads
While Orion is doing well, one of the ten CubeSat payloads launched on the same rocket – Japan’s “OMOTENASHI” lunar lander – will not complete its mission.
OMOTENASHI – the Outstanding MOon Exploration TEchnologies demonstrated by the NAno Semi-Hard Impactor Mission – is a 6U CubeSat containing a small (0.715 kg) surface probe designed to crash into the Moon.
The probe features an inflatable airbag and shock absorption system made of frangible material and epoxy fill, designed to survive surface impacts with target velocities of 50m/s vertical and 100m/s horizontal. At this speed, OMOTENASHI offered the opportunity to test another way of delivering payloads to Luna.
Unfortunately, CubeSat’s radios did not respond long after launch, and the orbit chosen for OMOTENASHI gave it only one chance to activate its thrusters and head for the lunar surface.
Japan’s space agency today reported it could not establish contact with OMOTENASHI and was therefore unable to send the commands to initiate the landing sequence.
Another Japanese CubeSat on the Artemis mission, the Lunar Earth Point 6U spacecraft EQUilibriUm (EQUULEUS), is behaving as expected in its mission to measure plasma in the Earth-Moon system.
Return to sender
Orion will perform a descent burn to free itself from the DRO, which will take it to within 60 miles of the lunar surface and on course home. The craft has yet to make a fire, however, and this is where things start to get interesting.
The final blast is combined with a gravitational assist from the moon that “sling Orion onto a homeward trajectory where Earth is being accelerated [it] up to a speed of about 25,000 mph (40,233 km/h),” NASA said.
For reference, Orion cruised at 5,102 mph (8,210 km/h) after completing the two-minute burn that took it around the far side of the moon.
Traveling at 25,000 miles per hour has a side effect that NASA is counting on for another test of the Orion system: It will heat the capsule to about 5,000°F (2,760°C) during atmospheric reentry — half that the temperature of the sun’s surface.
But first things first, let’s launch the spacecraft into its lunar orbit and celebrate our return to the moon (albeit a long way away), after 53 years of looking up and asking “what ifs?”.
After Orion appeared from the far side of the moon and images of Earth were beamed back, Flight Director Zeb Scoville had a chance to articulate what many were thinking as Orion flew through the void. “This is one of those days that you’ve thought and talked about for a long, long time.” ®
https://www.theregister.com/2022/11/21/orion_reaches_the_moon_buzzes/ Orion reaches the moon, hums to the surface, and prepares for orbit • The Register