What is NASA’s giant SLS rocket?

NASA has developed a huge rocket called the Space Launch System (SLS) to launch astronauts to the moon and ultimately to Mars. Set to make its debut in November 2021, the SLS is the most powerful launch vehicle built since the 1960s.

NASA plans to send a man and woman to the lunar surface by 2024, in the first landing with humans since Apollo 17 in 1972.

For the past 20 years, astronauts have made routine trips to and from the International Space Station (ISS).

But the Moon is nearly 1,000 times farther than the ISS; getting the astronauts there requires a monstrous rocket.

The SLS is the modern equivalent of the Saturn V, the huge launcher built during the Apollo era. Like Saturn, it is divided into segments, or stages, stacked on top of each other. But the rocket also incorporates space shuttle technology.

The first version of SLS will be called Block 1. Over the next few years it will undergo a series of updates so that it can launch heavier payloads to destinations beyond low earth orbit.

Block 1 SLS will tower 23 floors above the launch pad, making it taller than the Statue of Liberty.

“It’s really a huge rocket. It’s just astounding,” said John Shannon, vice president and program manager for SLS at Boeing, the main contractor for the rocket. He told BBC News in 2019: “When you see the SLS put together, you haven’t seen anything like it since the Saturn V.”

The rocket will launch astronauts aboard NASA’s next-generation crew vehicle, Orion, bringing it to the speed needed to exit low Earth orbit and travel to the Moon.

How the rocket works

The SLS consists of a giant central stage flanked by two solid rocket repeaters (SRBs). The core houses two large storage tanks: one for liquid hydrogen, the fuel, and another for liquid oxygen, an “oxidizer”, which causes the fuel to burn.

Together, these are known as propellants.

At the base of the main stage are four RS-25 engines, the same ones that powered the spaceplane-like shuttle orbiter, retired in 2011.

When liquid hydrogen and oxygen are fed into the engine chambers and ignited with a spark, the chemical reaction produces large amounts of energy and vapor.

Steam exits the engine nozzles at speeds of 16,000 km / h (10,000 mph) to generate thrust, the force that propels a rocket through the air.

SRBs give the rocket extra power to escape the clutches of gravity. These twin boosters are over 17 stories tall and burn six tons of solid fuel per second. They provide 75% of the total thrust during the first two minutes of flight.

The most powerful rocket ever?

If we use thrust as a measure, the SLS will be the most powerful rocket ever when it flies into space in 2021. The Block 1 SLS will generate 8.8 million pounds (39.1 Meganewton) of thrust at launch, 15% in more than the Saturn V.

In the 1960s, the Soviet Union built a rocket called N1 in an attempt to reach the moon. Its first stage could produce 10.2 million pounds (45.4 Meganewtons) of thrust. But all four test flights ended in failure.

A future version of the SLS – called Block 2 cargo – is expected to approach the thrust levels of the N1. But a vehicle called the Starship, developed by Elon Musk’s SpaceX company, is expected to outperform both, producing up to 15 million pounds (66.7 Meganewtons) of thrust. The spaceship is currently under development, although there is no exact date for its first flight.

The SLS in numbers

• The rocket will resist 98 m (322 ft) high in its initial configuration, or Block 1

• Block 1 SLS can send more than 27 tons (59,500 lbs) to the lunar orbits – the equivalent of 11 large SUVs (SUVs)

• A future version of SLS will be launched, called Block 2 Cargo 46 tons (101,400 lbs) to the moon. They are 18 large SUVs.

• The SLS will produce 8.8 million pounds (39.1 Meganewtons) thrust in its Block 1 configuration

• four The RS-25 engines are located at the base of the main stage; they are the same used in the space shuttle

How shuttle technology was reused

The main stage of the SLS is based on the outer foam-covered tank of the space shuttle. This tank fed propellant to three RS-25 engines in the rear of the shuttle’s orbiter. Solid rocket thrusters play roughly the same role in both vehicles.

But the SLS is a very different beast. A number of shuttle-derived components and structures have undergone significant design changes due to the varying stress levels the SLS is subjected to.

As an example of these different stresses, in the space shuttle, the RS-25 engines were tilted upward and away from the solid rockets. Moving them close to the SRBs exposes them to further tremors. As a result, every system in the complex section of the SLS engine had to be rigorously tested to ensure it could withstand vibration.

Why was SLS built

In February 2010, the Obama administration canceled Constellation – George W. Bush’s plan to return to the moon by 2020. The news came as a devastating blow to workers in five southern states – Alabama, Florida, Louisiana, Mississippi and Texas – where NASA’s human spaceflight program has funded tens of thousands of jobs.

Some legislators in Congress were furious. Richard Shelby, a Republican senator from Alabama, said Congress will not “sit and watch the reckless abandonment of sound principles, a proven track record, a steady path to the success and destruction of our human spaceflight program.”

As a compromise, lawmakers in the affected states insisted on a single super-heavy rocket to replace President Obama’s canceled Constellation launchers.

The SLS project, based on NASA technical studies, was unveiled in 2011. After construction began, delays and cost overruns gave ammunition to critics, who thought NASA had to rely on rockets operated by suppliers commercial.

A recent oversight report says NASA will have spent more than $ 17 billion on SLS by the end of fiscal 2020.

But with the rocket’s development phase now over, success in a series of eight “Green Run” tests conducted on the main stage should pave the way for launch in 2021.

John Shannon, who has been in charge of SLS at Boeing since 2015, explained: “I suspect that once SLS is available nationwide there will be no need for another heavy vehicle like this for many years. So this is really a ‘ unrepeatable opportunity “.

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