Artemis 1’s flight to the Moon depends on a powerful rocket, precise timing

Even using it the most powerful rocket ever built by NASA, getting the agency’s unmanned Orion spacecraft to the Moon for the Artemis 1 test flight won’t be easy. It will rely on a complex series of precisely orchestrated maneuvers in deep space.

Mission planners had to account for the ever-changing positions of Earth and the Moon to ensure that the Space Launch System rocket would accurately deliver Orion to a moving point in low Earth orbit for the critical “translunar injection” — TLI — rocket that will start the journey to the moon.

They had to design an orbit that would send Orion to within 60 miles of the moon’s surface for a flight that would bend its path toward the planned “far retrograde orbit”—one that would take the capsule farther from Earth than any other classification than man. spacecraft.

A visual timeline of major events in the Space Launch System rocket’s ascent into space boosting an unmanned Orion crew capsule into orbit for the Artemis 1 mission to the moon. / Credit: NASA

The orbit must minimize the time the solar Orion is in the moon’s shadow while setting up a final lunar flyby to precisely target the capsule’s drop in the Pacific Ocean during the day as Earth moves through space and spins on its axis. .

All of these factors contributed to a two-hour launch window that opens at 8:33 AM. EDT on Monday, when, if all goes well, the 322-foot high Space Launch System rocket will explode from block 39B at the Kennedy Space Center.

Generating 8.8 million pounds of thrust at launch, the SLS rocket will propel Orion, its service module and booster upper stage into an initial orbit, one with a high point, or apogee, of about 1,100 miles and a low point, or perigee. only 18 miles.

Ten minutes after separating from the SLS core stage, but still attached to the Intermediate Cryogenic Propulsion Stage, or ICPS, the Orion capsule’s service module, provided by the European Space Agency, will deploy four directional solar panels to begin the recharging the batteries.

ICPS’s single Aerojet Rocketdyne RL10B engine will fire for the first time when the spacecraft approaches the high point of the orbit about 51 minutes after launch. The effect of the “burn” will raise the low point of the orbit from 18 to about 115 miles.

SLS’s two-hour lunar launch window is defined by the requirement for the ICPS to reach a point in space on the opposite side of Earth from the moon, known as the antipodes, where it can fire its engine to exit Earth orbit and to direct. for the moon.

This point is constantly moving as the Earth rotates and moves along its orbit around the sun, while the moon moves in its orbit around the Earth. The Artemis 1 orbit is designed so that the rocket’s perigee is synchronized as needed with the antipode so that a motor launch can send Orion to a point in space where the moon will be five days later.

An artist's impression of the Orion spacecraft during 18 minutes

An artist’s impression of the Orion spacecraft during 18 minutes

At that time, one hour and 36 minutes after launch, the ICPS’s RL10B engine will fire for 18 minutes, the longest burn ever attempted by this engine family, increasing the spacecraft’s speed to about 22,600 mph and effectively increasing the high point of the orbit near the moon.

Half an hour after the TLI engine is fired, the Orion capsule will separate from the ICPS to fly on its own. From that point, ICPS will continue to the moon — deploying a dozen small science research satellites, called CubeSats, along the way — before firing the booster to head into a “drop” orbit around the sun.

Orion flight controllers, meanwhile, will test the Orbital Maneuvering System engine that powers the capsule’s service module by performing four orbit correction maneuvers. These will create a critical “flyby outfeed” motor firing.

“This is the big burn that will really move Orion and send it into its planned long retrograde orbit (around the moon),” said lead Flight Director Rick LaBrown. “So when we do that burn and go by the moon, we’ll be about 60 miles from the surface. It’s going to be spectacular.”

    / Credit: NASA

/ Credit: NASA

The outgoing power flyby will occur over the far side of the moon when Orion is out of contact with mission control.

“So we’ll pray and I’ll hold my breath,” LaBrode joked. “But (we are) confident that everything will be fine.”

After a slingshot loop around the moon, another burn will put the craft into the planned far retrograde orbit.

Cameras inside and outside

Throughout the flight, cameras inside and outside Orion will document the view, beaming selfies and shots of the spacecraft, the moon and Earth, including planned views of Earth’s sunrise over the edge of the moon that resemble famous shot from the Apollo 8 mission that came to symbolize the environmental movement.

Earth as photographed by Apollo 8 astronauts on December 24, 1968. / Credit: NASA

Earth as photographed by Apollo 8 astronauts on December 24, 1968. / Credit: NASA

All the while, flight controllers will test Orion’s systems and collect a steady stream of engineering telemetry to document the spacecraft’s performance in the deep space environment. The service module will be closely monitored since the Artemis 1 mission will last twice as long as the 21-day module design certification.

“We’re anticipating public affairs where we might be maneuvering, taking a selfie of Orion with the moon in the background or the Earth in the background,” LaBrode said. “We’ll try to catch Earthrise. That’s an impressive sight.”

On September 8, Orion will be further from Earth than the record set by the Apollo 13 crew – 248,654 miles – as it flies one and a half laps around the moon in this far-flung orbit.

The long journey home

The journey home will begin on September 21, when the service module’s engine is fired again to escape from distant retrograde orbit and head back toward the moon. Three days later, thanks to the changing geometry of the Earth, the Moon and the spacecraft, Orion will reach its maximum distance from Earth of 280,000 miles.

On October 3, the service module engine will be fired up again as Orion makes another lunar flyby, this one at an altitude of about 500 miles. The “return powered flyby” burn will ensure that Orion re-enters Earth’s atmosphere at the precise point it needs to make a daytime splashdown in the Pacific Ocean about 50 miles west of San Diego.

If all goes according to plan, Orion will return to Earth on October 10. Twenty minutes before atmospheric entry, the capsule will separate from the no-longer-needed service module and orient itself so that the 16.5-foot-wide heat shield faces the direction of travel.

Flight controllers will attempt to capture images from the East of Earth as the Orion spacecraft orbits the moon.  / Credit: NASA

Flight controllers will attempt to capture images from the East of Earth as the Orion spacecraft orbits the moon. / Credit: NASA

The capsule will then hit the top of the distinct atmosphere at an altitude of 400,000 feet while traveling at nearly 25,000 mph. The spacecraft will sink into the atmosphere to slow down and then resurface like a rock skipping a lake. It will re-enter moments later, enduring temperatures of up to 5,000 degrees as atmospheric friction slows the craft to about 300 mph.

“We actually do what’s called an entry skip profile,” explained Entry Flight Director Judd Frieling. “So we’re going to hit the entry interface at 400,000 feet and then we’re going to immediately start controlling the lift vector of the capsule so that we sink a little bit into the atmosphere and then come back a little bit and then re-enter. Once we exit that second period, we will continue our journey to the splashdown location.”

Orion will fly a bay cover by parachute at an altitude of 35,000 feet using 3 small ducts that, in turn, will eject two 23-foot-wide parachutes that will stabilize the spacecraft and help it slow to about 130 mph.

The Orion spacecraft will hit the discernible atmosphere at an altitude of 400,000 feet at nearly 25,000 mph.  / Credit: NASA

The Orion spacecraft will hit the discernible atmosphere at an altitude of 400,000 feet at nearly 25,000 mph. / Credit: NASA

Three 11-foot-wide pilot parachutes will then deploy, pulling the capsule’s three 116-foot-wide main parachutes to an altitude of about 6,800 feet. The mains will slow the descent to a relatively gentle 17 mph for launch.

Estimated time to ship to splashdown: 42 days, 3 hours and 20 minutes.

“Once we’re splashed down, we’ll let the vehicle run for about two hours,” Frieling said. “We’re going to do some tests there, thermal tests, to make sure we have adequate cooling for the astronauts when we finally have them on board and we’re waiting for the recovery crews to pick them up.

“And then, after that two-hour period, we’ll disable the vehicle and turn it over (to) the recovery team that’s over there on a Navy vessel.”

A joint Navy and NASA recovery team based on the USS Portland will collect the main and drogue chutes before attaching cables and towing Orion to the ship’s well deck, a type of enclosed dock that can be flooded or dry.

The Orion will be towed into the flooded chamber and placed on top of a mounting fixture. As the water is pumped out, the capsule will settle into the pod for shipment back to the US Naval Base in San Diego and, from there, to the Kennedy Space Center for detailed inspection.

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