NASA is building a giant rocket called the Space Launch System (SLS) to send astronauts to the moon—and, after that, to Mars.
With a debut scheduled for November 2021, the SLS is the most powerful launch vehicle built since the XNUMXs.
NASA has plans to send a man and a woman to the surface of the moon by 2024, which would be the first human landing since Apollo 17 in 1972.
For the past 20 years, astronauts have routinely traveled to and from the International Space Station (ISS).
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But the Moon is almost 1.000 times farther than the ISS; for astronauts to reach it, a monstrous rocket is needed.
The SLS is the modern equivalent of the Saturn V, the huge launcher built during the Apollo era.
Like Saturn, this rocket is separated into segments, stacked on top of each other. But this rocket also contains space shuttle technology.
The first version of the SLS will be called Block 1. In the coming years, it will undergo a series of refinements to be able to launch increasingly heavy payloads to origins beyond low Earth orbit.
Block 1 SLS will rise 23 stories above the launch pad - making it taller than the Statue of Liberty.
"It's a truly massive rocket. You're amazed at how tall it is," says John Shannon, SLS vice president and program manager at Boeing, the primary contractor for the rocket. He told BBC News in 2019: "When you see the SLS assembled, you realize that nothing like it has been seen since Saturn V."
The rocket will launch astronauts aboard NASA's next-generation Orion crew vehicle, bringing it to the speeds necessary to leave low Earth orbit and continue on to the Moon.
How a rocket works
The SLS consists of a giant central core flanked by two solid propellant boosters (SRBs). In the central core are two large tanks: one for liquid hydrogen, the fuel, and the other for liquid oxygen, the "oxidizer," which makes that fuel burn.
Together, they make up the propellant.
At the bottom of the central core are four RS-25 engines, the same ones that powered the Space Shuttle Orbiter, retired in 2011.
When liquid hydrogen and oxygen are injected into the engine chambers and ignited by a spark, a chemical reaction produces a huge amount of energy and steam.
Steam exits the engine's nozzles at 16.000 miles per hour to produce thrust - the force that propels the rocket through the air.
Solid propellant boosters give the rocket extra power to eject itself from the jaws of gravity. These two twin boosters are over 17 stories tall and burn six tons of solid propellant every second. They provide 75 percent of the total thrust during the first two minutes of flight.
The most powerful rocket of all time?
If we use thrust as a measure, in 2021 the SLS will be the most powerful rocket ever launched into space. Block 1 SLS will generate 8,8 million pounds (39,1 meganewtons) of thrust at launch, 15 percent more than the Saturn V.
In the 1s, the Soviet Union built a rocket called the N10,2 in an attempt to reach the moon. Its first stage could produce 45,4 million pounds (XNUMX meganewtons) of thrust. But all four test flights were unsuccessful.
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A future version of the SLS - called Block 2 Cargo - should approach the level of thrust possessed by the N1. But a craft called Starship, built by Ilona Musk's company SpaceX, is set to surpass both - producing as much as 15 million pounds (66,7 meganewtons) of thrust. The starship is currently under construction, but there is no scheduled date for its first flight.
SLS in numbers
- The rocket will be 98 meters tall in its original, or Block 1, configuration
- Block 1 SLS can send more than 27 tonnes into lunar orbits - the equivalent of 11 giant SUVs
- Future versions of the SLS, called Block 2 Cargo, will launch 46 tons to the Moon. That's 18 large SUVs.
- SLS will produce 8,8 million pounds (39,1 meganewtons) of thrust in Block 1 configuration
- Four RS-25 motors are located at the bottom of the central core; the same ones are used in the space shuttle
How shuttle technology was reused
The central core of the SLS is based on the foam-lined outer space shuttle tank. This tank supplied propellant to the three RS-25 engines on the back of the shuttle orbiter. Solid fuel boosters play a very similar role in both aircraft.
But the SLS is a very different beast. A large number of components and structures taken over from the shuttle have undergone significant design changes due to the different pressure levels SLS exposes them to.
As an example of the difference in these pressures, in the space shuttle the RS-25 engines were tilted and placed far from the solid fuel boosters. Moving them closer to the boosters exposes them to more thrashing. As a consequence, every system in the SLS's complex engine section had to be rigorously tested to ensure it could withstand vibration.
Why was the SLS made?
In February 2010, the Obama administration abolished is Constellation - George Bush's plan to return to the moon by 2020. The news was a blow to workers in five southern states - Alabama, Florida, Louisiana, Mississippi and Texas - where NASA's human spaceflight program financed tens of thousands of jobs.
Some members of Congress were very angry.
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Richard Shelby, Republican Senator from Alabama, He said that Congress "will not just sit back and watch solid principles, a proven track record of achievement, and a sure path to success be carelessly abandoned and our space flight program destroyed."
As a compromise, lawmakers from the affected states insisted on a single super-heavy rocket to replace the Constellation launchers that were scrapped by President Obama.
SLS blueprint, based on NASA's technical studies, it was disclosed in 2011. After work on it began, delays and cost overruns prompted critics to rant that NASA should rely on rockets operated by commercial suppliers.
But without significant modifications, no existing booster has enough power to send Orion, astronauts and a large payload to the Moon in a single flight. Currently, only SLS has this capability.
A recent report on the project says that NASA will to spend more than $17 billion on SLS by the end of fiscal year 2020.
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But now that the rocket's development phase is over, success in a series of eight tests The "green flight" performed on the central core should enable the launch in 2021.
John Shannon, who has been in charge of SLS at Boeing since 2015, explained, “I suspect that once SLS proves successful on a national scale, there will be no need for another heavy-lift aircraft like this for many years. So this is truly a once-in-a-generation opportunity."
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