Thu. Jun 1st, 2023
Different configurations of the SLS rocket.
enlarge / Different configurations of the SLS rocket.

NASA will likely launch its first astronauts into deep space since the Apollo program on a less powerful version of its Space Launch System rocket than originally planned. Although it has not been officially announced, in recent weeks the space agency’s mission planners have begun designing “Exploration Mission 2” to be launched on the Block 1 version of the SLS rocket, which can lift 70 tons to a low altitude. orbit around the earth.

Acting Administrator Robert Lightfoot confirmed at a congressional hearing on Thursday that NASA is seriously considering launching humans to the moon on the Block 1 SLS. “We’ll change the mission profile if we’re flying with humans and we’re using the Interim Cryogenic Propulsion Stage (ICPS), because we can’t do what we could do if we have the Exploration Upper Stage,” Lightfoot said.

The main difference between the original configuration of the SLS rocket — on which NASA has spent more than $10 billion since 2011 — and its successor is the top stage that sits atop the booster. Under current plans, the weaker upper stage, known as the ICPS, would only fly once — on the SLS rocket’s maiden flight in 2020. Then NASA would switch to a new, much more powerful second stage that would improve the overall performance of the rocket. the SLS rocket by about 50 percent.

Now NASA will probably fly the SLS rocket in its Block 1 configuration at least two or even three times before introducing the more powerful variant of the booster. By doing so, it can move humans into deep space faster. The current 2023 launch date for the deep space Exploration Mission 2 could move forward, a NASA spokeswoman confirmed. “The earliest possible launch date is under review and a formal decision is expected in the coming months,” she added.

Even with a Block 1 SLS, NASA should be able to fly this mission profile for Exploration Mission 2, but without the nine-ton payload.

Even with a Block 1 SLS, NASA should be able to fly this mission profile for Exploration Mission 2, but without the nine-ton payload.

However, this decision also suggests that the agency is far from developing the powerful Exploration Upper Stage, which NASA says it needs to run an ambitious lunar exploration program. This could delay meaningful exploration in and near the moon in the mid and late 1920s at the earliest.

Mobile Launcher

Until a few weeks ago, NASA didn’t have the ability to fly crew members on an ICPS upper stage. However, thanks to Congress, the agency may now consider flying the Block 1 version of the SLS missile multiple times. Last month, as part of the fiscal 2018 budget deal, Congress appropriated $350 million for a new piece of hardware: a mobile launch tower to be built at the Kennedy Space Center in Florida.

NASA already has one of these massive towers, which will support the testing and maintenance of the SLS rocket, as well as move it to the launch pad and provide a platform from which it will launch. After the maiden flight of the SLS rocket, NASA planned to spend 33 months rebuilding the tower to handle the larger, more powerful version of the SLS with the Exploration Upper Stage. With the additional congressional funding, it can now begin building that second tower and continue to use the existing mobile launch tower for Block 1 SLS launches.

Lightfoot said on Thursday that the agency was just beginning to process how best to use this Congressional generosity, which had not been sought in the White House budget. “You’re going to have to give us some time — it was only a few weeks ago that we found out we got that — to be able to understand the flow,” Lightfoot said.

Delays in the upper phase

NASA’s consideration of flying the first manned mission into deep space on an SLS rocket with the ICPS upper stage supports the idea that the space agency is struggling to develop the Exploration Upper Stage. Sources have told Ars that the cost of this program has increased beyond expectations. Originally this 18 meter high stage was to be powered by four RL-10 rocket engines. However, in a request late last year, NASA indicated it was looking for cheaper engines to power the stage. NASA has also made other requests to the industry, indicating that it is concerned about the cost of the upper stage.

During an interview this week, Wayne Hale, a former space shuttle program manager who is a member of NASA’s advisory board, said it will likely take four or five years from this point to develop and construct the Exploration Upper Stage.

“You’re building a brand new rocket,” Hale said. “It’s not just a tank with a few engines bolted to it. It has to be aerodynamic. It has to be able to absorb the shocks and vibrations of the launch. It has to be started pretty much from scratch. So yeah, it’s complicated.”


By launching at least one crewed mission or more with the base, Block 1 rocket buys NASA time for the development of the new upper stage, without the embarrassment of long gaps between flights of the SLS rocket. But the decision does not come without challenges, either. Astronauts have never flown on a rocket with the ICPS, so it would have to be a time-consuming and expensive process to “human-assess” the hardware.

With the ICPS, the flight profile for Exploration Mission 2 would still include a manned checkout of Orion’s high-Earth orbit systems, a lunar flight, and a free return trajectory back to Earth. However, flying this mission on a Block 1 SLS would rule out a co-manifest payload that was planned. NASA hadn’t yet specified this payload for the first manned flight, but it could have weighed up to nine tons. Without the Exploration Upper Stage, NASA can’t fly in one flight with crew members and parts of a deep space gateway it hopes to build near the moon by the 2020s.

In addition, by continuing to fly the SLS rocket in its Block 1 configuration, NASA is opening up to criticism that its own heavy-lift rocket is not that much more powerful than the commercial options available now or in a few years. . Both SpaceX’s Falcon Heavy rocket and Blue Origin’s New Glenn have a lift capacity of about 50 tons to low Earth orbit. However, they cost only a fraction of what the SLS needs to build and fly.

By akfire1

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