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Home / Science / ULA Atlas 5 is NASA’s go-to rocket for nuclear-powered space probes – Spaceflight Now

ULA Atlas 5 is NASA’s go-to rocket for nuclear-powered space probes – Spaceflight Now

Consumer Bruno, president and CEO of United Launch Alliance, creates the Atlas 5 rocket that launches NASA’s Mars 2020 Perseverance rover. Credit: NASA / Ben Smegelsky

NASA’s Perseverance rover, set up for removal on Thursday on a trip to Mars, would have posed unusual challenges for launch crews working with the plutonium-powered power generator, but the Atlas 5 rocket of the United Alliance Launch is the only one suitable for the job, said the company’s CEO.

The 197-foot-tall (60-meter) Atlas 5 rocket rolled to pad 41 Tuesday morning at Cape Canaveral Air Force Station, which is moving into a blastoff position Thursday during an opening two hours at 7:50 am EDT (1150 GMT).

Four powerful strap-rocket boosters grouped around the base of the Atlas 5 give it an extra burst of speed in the first minute and a half of flight. The boosters, made by Rocketdyne Aerojet, will connect to the Atlas 5’s main engine built in Russia to provide about 2.3 million pounds of traction to push the rocket off the ground.

One RL10 engine on the top stage of Atlas 5’s Centaur will deliver the Mars 2020 spacecraft on a trajectory away from Earth at a relative speed of 24, 785 mph, or about 11 kilometers per second. That’s fast enough to be destroyed without Earth’s gravitational grasp.

The Mars 2020 spacecraft weighs about 9,000 pounds, or 4.1 metric tons, on the Atlas 5 rocket. The entire vehicle at launch will weigh about 1.17 million pounds, or 531 tons.

“This rocket is going to exceed the pad with this relatively tiny weight, so it doesn’t flash when they say ignition,” said Tory Bruno, president and CEO of the United Launch Alliance, the 50-50 joint venture between Boeing and Lockheed Martin to build Atlas 5 rockets.

Bruno said the Atlas 5 rocket, set for its 85th flight since debuting in 2002, is strong and ready for the start of Thursday morning’s countdown.

“The Atlas is going, Centaur is going, and we’re literally knocking on the little ones to take this nuclear-powered dune buggy on Mars,” Bruno said.

The Atlas 5 will exceed the speed of sound just 35 seconds after it fired away from Cape Canaveral, heading southeast from the Florida Space Coast over the Atlantic Ocean. After starting the four strap boosters on T + plus 1 minute, 49 seconds, the Atlas 5 kerosene-fired RD-180 engine will continue to turn on to launch the rocket into space.

On T + plus 3 minutes, 27 seconds, the Atlas 5 will release its heavy-duty naft that protected the Mars 2020 spacecraft during the first few minutes of flight from into the thickest layers of the atmosphere. The main RD-180 engine will run until T + plus 4 minutes, 22 seconds, when the Atlas 5 will fly at 13,470 mph (21,680 kilometers per hour) some 309 miles (497 kilometers) down Cape Canaveral .

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The first burn from the Centaur stage RL10C-1 engine, which produces 22,900 pounds of traction, will put the Mars 2020 spacecraft into a low-altitude parking orbit around the Earth around 11 a minute and a half after departure. After the coast on the Atlantic Ocean and South Africa, the Centaur stage will capture its RL10 engine for the second time for an eight-minute maneuver to stretch the Mars 2020 spacecraft to escape by speed.

After shutting down the engine nearly 53 minutes into the mission, the Centaur stage will send the Mars 2020 spacecraft into T + along with 57 minutes, 32 seconds.

The $ 2.7 billion mission is to reach Mars and Earth on February 18, 2021.

The Mars-bound rover carries a Radiototope Missions Thermoelectric Generator Filling Missions containing 10.6 pounds (4.8 kilograms) of ceramic-shaped plutonium dioxide fuel. The generator will produce electricity to power the Perseverance rover during its mission.

Radioactive fuel is inserted into many layers of the blast’s protective shield to ensure that it does not crack in the event of a launch damage.

“It’s a very safe device, but it’s still close to 11 pounds of plutonium, so there are significant handling restrictions associated with it,” Bruno said in an interview Wednesday with Spaceflight Now. It’s a thermoelectric device and always emits a few kilowatts of waste heat, so there are special handling considerations involved in that. “

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

The device produces about 110 watts of power at the start of the Perseverance mission, roughly equivalent to the pulling power of a light bulb. The energy efficiency of MMRTG decreases by a few percent per year.

The MMRTG will charge two lithium-ion batteries on the Perseverance rover. The batteries will light up the robot at peak power usage times, when NASA says power demand could reach 900 watts during science operations on Mars.

Nearly 95 percent of the energy produced by MMRTG will be in the form of overheating. That helps keep the rover’s Perseverance interior electronics in the cold Martian surface temperatures.

But before launch, the heat produced by the nuclear power generator poses challenges to the cooling systems inside the Atlas 5 assembly building. That is why the teams waited to install the MMRTG on the rover last week, a few days before Atlas 5 leaves the Vertical Integration Facility for pad 41 for the final countdown preps.

The payload cutter surrounding the Mars 2020 spacecraft on the Atlas 5 rocket has a large access door, which allows engineers enough space to fit the nuclear device – which measures a bit larger than a bucket. 5 gallon – through the laser and mounted on the rover.

“We configured our Vertical Integration Facility with a dedicated clean portable room, so we could put the rocket in there, integrate the spacecraft, turn it on, and then right at the end … we put the MMRTG through of the VIF, come into that giant hatchway, and then install it with a clean working room, ”Bruno said.

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

Bruno said the clean mobile room set up inside the ULA vertical rocket hangar allowed ground crews to mount the MMRTG on his spacecraft in a pristine environment to meet strict “protection” protocols. planetary “.

“Protecting the planet makes us have to be very careful not to pollute the biological (material) lander because we’re looking for life on Mars, and if it brings life to you, that kind of messs that experiment,” he said Bruno.

“The other part of it obviously is the reliability of Atlas,” Bruno told Spaceflight Now. “We have to make sure that this multi-billion dollar mission goes to Mars. We also have to make sure that nothing happens to the MMRTG during that mission, even though they are meant to withstand rocket failure, and even re-entry. This has happened in the past. Again, it’s a very safe device, but you have to be and be extra, be more careful. “

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

NASA’s nuclear-powered spacecraft will be the Dragonfly, a rotorcraft in the air that will launch in 2026 for Saturn’s moon Titan. NASA has not yet selected a rocket for that mission.

The cut-off perspective using the Atlas 5 rocket shows the unique access doors used to inspect the Mars 2020 spacecraft and to install the rover’s nuclear power source. Credit: NASA / Ben Smegelsky

There is another change in the Atlas 5 rocket for nuclear-powered cargo missions, according to Omar Baez, director of NASA’s launch for the Mars 2020 mission. The modification is in the a pyrotechnic system that is activated 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 reached orbit successfully on all 84 of its missions to date.

“If you’ve had any kind of accident, that’s to prevent the MMRTG from being a danger to the public,” Baez said. “So we try to be very precise in destroying, for example the Centaur (upper stage), so that the MMRTG is harmless, where it can harm the public.”

Baez said the same type of ordering system was used on the Atlas 5 rocket launched by the Curiosity Mars rover in 2011. The Perseverance rover is similar in design to curiosity, but carries a different set of scientific instruments.

“We are humble to be trusted with such an imp mission,” Bruno said. “We are obviously proud to have flown all U.S. missions to Mars.

“This is special because it’s more sophisticated, and it’s a more complex mission, and somehow it’s potentially more meaningful than all the ones that came before,” Bruno said. “The instrumentation he has to pave the way for future human exploration, to experiment by making oxygen, and of course, he’s putting it on Jezero Crater, which is this ancient river delta. We know that on Earth those the types of geological formations have sedimentary deposits that have been able to preserve evidence for microbial life for billions of years.

“This is truly the best chance to find evidence of Martian’s ancient life,” he continued. “The other element that’s interesting is that it’s really tied to future missions in a way that other missions haven’t done, by caching the samples. It’s going to collect Martian surface samples and place them in different places, and then there will be future missions planned to come and get them.

“So it’s really, really exciting. It has the potential to open up a whole new path of exploration. Oh my gosh, if you find evidence of ancient life, it will change our perception or our place in the universe. “

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Follow Stephen Clark on Twitter: @ StephenClark1.

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