Atlas 5 of ULA is a rocket – Spaceflight Now for nuclear-powered space probe by NASA

Tory Bruno, president and CEO of United Launch Alliance, has become one with the Atlas 5 rocket that will launch NASA’s Mars 2020 Perseverance Rover. Credit: NASA / Ben Smagelski

NASA’s Perseverance Rover, scheduled for liftoff Thursday on a trip to Mars, posed some unusual challenges for launch crews working with the robot’s plutonium-fueled power generator, but the Atlas 5 rocket of the Joint Launch Alliance’s job Is uniquely suited to, says the company’s CEO.

The 197-foot-long (60-m) Atlas 5 rocket rolled onto the pads at Cape Canaveral Air Force Station 41 on Tuesday morning, positioning it for a blastoff during a two-hour window opening at 7:50 am EDT (1150 km) Thursday. Gone. ).

Four strap-on solid rocket boosters clustered around the Atlas 5’s base will give it additional speed in the first minute-and-a-half of flight. The boosters, created by Aerojet Rocketdyne, will combine with the Atlas 5’s Russian-built RD-180 main engine to deliver 2.3 million pounds of thrust to land the rocket.

A single RL10 engine on the Atlas 5’s Centaur upper platform will deliver a Mars 2020 spacecraft on a trajectory from Earth with a velocity of 24,785 mph or about 11 kilometers per second. It is fast enough to break free from the grip of Earth’s gravity.

The Mars 2020 spacecraft weighs around 9,000 pounds or 4.1 metric tons on top of the Atlas 5 rocket. The entire vehicle will weigh approximately 1.17 million pounds or 531 metric tons during launch.

“This rocket is going to leap off the pad with this relatively small payload, so don’t blink when they say ignition,” said Tory Bruno, president of Boeing and Lockheing Martin’s 50-50 joint venture. Atlas makes 5 rockets.

Bruno said the Atlas 5 rocket, scheduled for its 85th flight since its 2002 debut, is healthy and ready for the start of Thursday morning’s countdown.

Bruno said, “Atlas is going, Centaur is going, and we’re literally kissing to take this nuclear-powered dune buggy to Mars.”

The Atlas 5 will exceed the speed of sound just over 35 seconds after firing away from Cape Canaveral, southeast from the Florida Space Coast over the Atlantic Ocean. After turning off four strap-on boosters in T + Plus 1 minute, 49 seconds, the Atlas 5’s kerosene-burning RD-80 engine will continue firing to power the rocket into space.

In T + Plus 3 minutes, 27 seconds, Atlas 5 will release its payload shroud shielding Mars’ 2020 spacecraft during the first few minutes of flight through the thick lower layers of the atmosphere. The RD-180 main engine T + plus will fire for 4 minutes, 22 seconds, when the Atlas 5 will fly at a speed of 13,470 mph (21,680 kilometers per hour) and 309 miles (497 kilometers) from Cape Canaveral.

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The first burn by Centaur Stage’s RL10C-1 engine, which produces a thrust of 22,900 pounds, will put the Mars 2020 spacecraft into a low-altitude parking orbit around the Earth about one-half-a-minute after liftoff. Passing over the Atlantic Ocean and over South Africa, the Centaur Stage will prompt its RL10 engine to take off the Mars 2020 spacecraft for an eight-minute maneuver to escape velocity.

After shutting down the engine for approximately 53 minutes in the mission, the Centaur Stage T + Plus will deploy the Mars 2020 spacecraft in 57 minutes, 32 seconds.

The $ 2.7 billion mission is due to reach Mars and land. February 18, 2021.

Mars-bound Rover maintains a multi-mission radioisotope thermoelectric generator containing 10.6 pounds (4.8 kg) of plutonium dioxide fuel in ceramic form. The generator will produce power to power the Perseverance Rover throughout its mission.

The radioactive fuel is shielded in several levels of protective explosion to ensure that it will not rupture in the event of a launch failure.

“It’s a very safe device, but it’s still close to 11 pounds of plutonium, so there are significant restrictions associated with it,” Bruno said in an interview with Spaceflight Now on Wednesday. It is a thermoelectric device, and it always turns off one-two kW of waste heat, so special handling considerations are included with it. “

Developed by the US Department of Energy, the MMRTG works by converting heat from the natural radioactive decay of plutonium-238 – a special non-weapon grade isotope of plutonium – into electricity. The generator contains 10.6 pounds (4.8 kg) of plutonium dioxide fuel.

The device produces about 110 watts of power at the beginning of the perseverance mission, which is equivalent to the power draw of a light bulb. The power efficiency of the MMRTG decreases by a few percent per year.

The MMRTG will charge two lithium-ion batteries on the Fixture Rover. The battery will power the robot during peak power use, when NASA says that power demand during science operations on Mars can reach 900 watts.

About 95 percent of the energy produced by MMRTG will be in the form of excess heat. This will help keep the Perseverance Rover’s internal electronics warm in cold temperatures.

But before the launch, the heat produced by the nuclear power generator poses challenges for the cooling system inside the Atlas 5’s assembly building. That’s why teams waited last week to install MMRTG on the Rover, just days before Atlas 5 was moved from the vertical integration facility to Pad 41 for the final countdown.

The payload fairing around the Mars 2020 spacecraft atop the Atlas 5 rocket has a large gateway, allowing engineers to fit nuclear equipment – which measures slightly larger than a 5-gallon bucket through the shroud – and place it on the rover. Mounts .

“We configured our vertical integration facility with a portable customized clean room so that we could get the rocket there, integrate the spacecraft, button it up and then on the right… through the VIR to the MMRTG, so that in Come up with that huge hatchway, and then install it with a clean room to run, ”Bruno said.

SpaceX’s Falcon Heavy rocket also has enough power to send the Mars 2020 spacecraft toward the Red Planet. But SpaceX does not, for now, have the ability to install payloads on Falcon Heavy in a vertical configuration. SpaceX plans to build a mobile gantry on Pad 39A to support that capability in the coming years.

Bruno said the mobile clean room installed inside ULA’s vertical rocket hangar allowed ground crews to mount the MMRTG, which places the spacecraft in an ancient environment to meet stringent “planetary protection” protocols .

“The protection of the planets wants us to be very careful not to contaminate the lander with biological (material) because we are looking for life on Mars, and if you brought life with you, that kind of messing would have happened Is, ”said Bruno.

“Of course the other part of it is Atlas’ credibility,” Bruno told SpaceFlight Now. “We must ensure that this multi-billion dollar mission reaches Mars. We also want to ensure that nothing happens to MMRTG during that mission, even if they are designed to withstand rocket failure, and even re-entry. The same thing has happened in the past. Again, this is a very safe tool, but you have to take extra, extra precautions. “

The MMRTG is the latest in a line of nuclear power sources and heaters used since 1961 on more than 30 US space missions. Atlas 5 has launched two of those probes in previous missions – Pluto and Curiosity Mars Rover from NASA’s New Horizons mission.

NASA’s next nuclear-powered spacecraft will be DragonFlu, an airborne rotorcraft that will launch in 2026 on Saturn’s moon Titan. NASA has not yet selected the rocket for that mission.

This view of the Atlas 5 rocket’s payload fairing shows the unique access doors used to inspect the Mars 2020 spacecraft and install the rover’s nuclear power source. Credit: NASA / Ben Smagelski

According to Omar Badge, NASA’s launch director for the Mars 2020 mission, the Atlas 5 rocket has undergone another change for missions with nuclear-powered payloads. Moderation is in pyrotechnic systems that will activate to destroy Atlas 5 if it deviates from its planned course and threatens populated areas.

Such an event is highly unlikely, and Atlas 5 has successfully reached orbit on all 84 of its missions to date.

“If you’ve had an accident of any kind, it’s to protect the MMRTG from danger to the public,” said Badge. “So we try to be very precise in destroying, for example the centaur (upper stage), in a way that MMRTG is not in the harem, where it can harm the public.”

Badge said the same type of armament system was used on the Atlas 5 rocket, which launched the Curiosity Mars Rover in 2011. The Persistence Rover is similar to the Curiosity’s design, but carries a different set of scientific instruments.

“We are humble to be trusted with such a mission,” Bruno said. “We are clearly proud of all of the US missions on Mars.

“It’s a special one because it’s more sophisticated, and it’s a more complex mission, and in a way it’s potentially more important than all that it was before,” Bruno said. “The instrumentation that has to make way for future human exploration is to experiment with making oxygen, and of course, they are placing it on the Jazero Crater, which is this ancient river delta. We know that those types of geological formations on Earth have sedimentary deposits that have been able to preserve evidence for microorganism life for billions of years.

“This really is the best chance to find evidence of ancient Martian life,” he continued. “The second element that is interesting is actually linked to future missions, not caching samples from other missions. It is going to collect samples of the surface of Mars and place them in different places, and then there will be plans for future missions that will come and get them.

“So this is really, really exciting. It has the potential to open up an entirely new transcendence. Oh God, if it finds evidence of ancient life, it will change our perception or our place in the universe. “

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