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Raumfahrt - Rocket Lab updates Neutron design

3.12.2021

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Rocket Lab's Neutron features a distrinctive design the company says is intended to enable the vehicle to be rapidly reused and be cost-competitive with other medium-class rockets. Credit: Rocket Lab

WASHINGTON — Rocket Lab released new details Dec. 2 of the design of its Neutron medium-class rocket, a vehicle with a unique design the company says is intended to enable frequent and low-cost reuse.

Rocket Lab unveiled the updated design of Neutron in a brief video presentation. The vehicle, made of carbon composite materials, is seven meters wide at its base, standing on fixed landing legs, and gradually tapers. That design intended to reduce heat loads on the vehicle during reentry before landing back at the launch site.

 

 

Rather than jettison the rocket’s payload fairing during launch, the “Hungry Hippo” fairing opens in four parts. Neutron then releases a lightweight, expendable upper stage with the payload before the fairing closes and the stage reenters. The vehicle will be able to place 8,000 kilograms into low Earth orbit while recovering the first stage, or up to 15,000 kilograms if the first stage is expended.

Neutron will be powered by a new engine called Archimedes, using methane and liquid oxygen propellants and generating about 225,000 pounds-force of thrust. The first stage will have seven Archimedes engines while the upper stage will have a single vaccum-optimized version of the engine.

“We’ve really optimized the vehicle from day one to be reusable. Every decision is based around that,” Peter Beck, chief executive of Rocket Lab, said in an interview.

That includes, he said, a design decision early on to be able to turn around that first stage for another launch within 24 hours of landing. “Not because I intend to relaunch the vehicle every 24 hours, but it drives all of the design decisions,” he said.

That design requirement, he said, led to decisions such as having the rocket return to the launch site rather than land on a barge. It was also a factor in the use of methane fuel rather than kerosene, as the latter creates soot that takes time to clean from engines.

While Archimedes is a new engine design, Beck said the company deliberately decided not to push the envelope in terms of its performance. “That’s an area where we’re not innovating,” he said. “What we’re trying to do is build an engine that is hugely reliable and can fly again and again.”

Instead, Rocket Lab is focusing on the structure of the vehicle. It will use carbon composite materials, as it does with the Electron rocket, but using a new technology called automated tape laying that enables composite structure to be built at rates of meters per minute. He noted that, by comparison, metallic 3D-printing technologies produce structures at the rate of millimeters per minutes.

“Poor mass efficiency in structures drives a requirement for high-performance engines, so if you can be really mass efficient in your structures, then you get to cheat on your engines,” Beck said, allowing the company to avoid what he called a “circle of doom” where increased mass of a vehicle component requires more propellant, which increases the mass of tanks and other structures.

Other companies, such as SpaceX when developing its Starship vehicle, have rejected composites because of their high costs versus metals like stainless steel. “Composites get a bad rap from people who don’t know how to make composites,” he said. “Our approach is incredibly fast and incredibly cost efficient.”

When Rocket Lab announced Neutron in March, the company said the first launch would be in 2024 from Wallops Island, Virginia. The company did not state a launch date or location in the Neutron update video presentation.

Beck said in the interview that 2024 remains the target date for a first launch. “It is a very steep development program to climb,” he said, but added that the company will take advantage of technologies previously demonstrated on Electron, from avionics to valves, for Neutron. The funds the company raised by going public through a SPAC merger will be sufficient to pay for Neutron’s development. “We hope to have something on the pad in 2024 and we’ll be pushing very aggressively to try to meet that.”

The company said in a statement it is “currently working through a competitive process to select launch site, rocket production facility and Archimedes engine test facility on the U.S. East Coast,” but Beck didn’t give a schedule for selecting it.

Rocket Lab has started to talk with potential customers of the vehicle, including those planning satellite constellations that Neutron is optimized to deploy. Beck mentioned interest from the U.S. Space Force, which awarded Rocket Lab $24.3 million in September to support work on Neutron’s upper stage.

Beck declined to give a launch price for Neutron, but said it would complete with other vehicles in its class on price. “There would be no point in building this vehicle if we didn’t think we could be incredibly cost-competitive with everything that is currently in operation and everything that is proposed.”

The Neutron design revealed in the video is different from what the company showed in March when it announced the vehicle. That earlier design looked like a more conventional launch vehicle with some similarities to the Falcon 9, notably landing legs folded against the side of the first stage.

“The Neutron rendering we put out was a very traditional launch vehicle. It would work, but it wasn’t achieving what we wanted to achieve,” he said of that original concept. “Partly we wanted to spend more time refining our design. Partly we’re sick of people copying us, so we just put something out there that people could copy all they want and it wouldn’t matter.”

Quelle: SN

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Neutron switches to methane/oxygen, 1 Meganewton Archimedes engine revealed

Rocket Lab has provided a significant update in the progress of their Neutron rocket, a vehicle aimed primarily at the small-scale interplanetary and low Earth orbit mega-constellation markets at first. 

Among the major updates announced by Rocket Lab CEO Peter Beck were a complete switch of propellants, a firm Return To Launch Site landing plan with the elimination of down-range ocean landings, reveal of the building materials, and introduction of the new 1 Meganewton Archimedes engine.

 

As previously announced

Neutron was revealed earlier this year on March 1 as a 40 m tall medium-lift launcher with a 4.5 m diameter payload fairing and a payload capacity to a 400 km low Earth orbit of 8,000 kg. In addition, the rocket would be capable of delivering roughly 2,000 kg to lunar orbit and 1,500 kg to Venus or Mars.

At the time, Neutron was slated to launch on its first mission in 2024 with initial missions planned from Launch Pad 0A at the Mid-Atlantic Regional Spaceport in Virginia. 

After boosting the vehicle toward orbit, Neutron’s first stage was designed to land on floating platforms downrange from the launch site in the ocean for recovery and reuse. Landing tests were planned to occur during operational flights so that the rocket would be available to customers during the period in which Rocket Lab worked out the landing and recovery process.

The base of Neutron, with its static landing legs, and the rocket’s stats behind Peter Beck (not to scale). (Credit: Rocket Lab)

Also among the elements announced for the rocket was the intention to allow Neutron’s design to eventually support human spaceflight activities — both in terms of low Earth orbit space station resupply missions and crewed flights.

At the time, no crew or cargo vehicle was in development.

Additionally, Rocket Lab stated the vehicle would utilize RP-1 kerosene and liquid oxygen as its propellants but did not specify the to-be-developed engine the vehicle would use nor the number of engines on each of its two stages — though Beck did tell NASASpaceflight later that it would be the “least amount of engines practical.”

Beck further said that Neutron would be capable of lifting 98% of all satellites forecast to launch through 2029 — potentially including batches of Rocket Lab’s own Photon satellites.

December 2 update

Today’s update announced several major and significant changes to the Neutron design, including the types of propellants it will use, its overall flight profile, as well as its composition.

 

 

Chief among the changes is the fact that Rocket Lab will no longer utilize deployable landing legs but instead utilize a fixed structure to eliminate as many potential failure points and create as simple of a design as possible.

Also gone is the RP-1 kerosene and liquid oxygen mixture, replaced with liquid methane and liquid oxygen that will fuel a new engine called Archimedes. This 1 Meganewton thrust engine will have a specific impulse, or Isp, of at least 320 seconds. Seven Archimedes engines will power the first stage.

Additionally, the payload fairings on Neutron will not deploy from the vehicle. Instead, at the end of the first stage burn, the top of the rocket will open like a clamshell — with renderings showing a four-plane separation system — to deploy the second stage that will continue taking the payload onward to its desired orbit or interplanetary destination. 

After second stage/payload deployment, the clamshell will close and the entire first stage and payload fairing combination will then perform a Return To Launch Site (RTLS) landing.

This RTLS landing profile is another major change in Neutron’s design, with Peter Beck previously mentioning that such a maneuver would stretch the rocket, which was something Rocket Lab was previously uninterested in doing but have since switched to as the design has evolved.

Neutron ends a mission with an RTLS landing. (Credit: Rocket Lab)

In another major reversal from March, downrange landings in the ocean are now no longer planned for the rocket, and missions that cannot return to the launch site would be expended —which would increase the total payload capacity of the rocket from 8,000 kg, with stage one return, to 15,000 kg with an expended first stage and fairings.

For the upper stage, Beck noted that it has competing design requirements. “It has to be the lightest and the most high-performing structure as part of the launch vehicle, but it also has to be the lowest cost because for Neutron, at least at this point in time, it’s a disposable stage.”

To this, and based on the clamshell design of the opening firings, the second stage is hung from the payload separation plane. According to Beck, Neutron’s second stage is “incredibly strong and the lightest upper stage ever in history.”

Overall, Neutron is now 7 m in diameter at its base with an increased payload fairing diameter of 5 m. The overall height of the rocket has not changed and remains 40 m.

The rocket will be made of Rocket Lab’s own carbon composite material. Peter Beck had previously noted that this material was not under consideration for reusable rockets, but in today’s update, he said, “Sometimes carbon composites get a tough rap because they’re expensive to manufacture and slow to produce. Not the case. We’re gonna do this fast.”

Seven Archimedes engines push the first stage of Neutron uphill. (Credit: Rocket Lab)

Beck went on to say that the plan is to use automated fiber placement. “3-D printing really changed the game when it came to rapid manufacture. With metallic 3-D printing, we measure the speed in millimeters per minute. With automated fiber placement, you measure the speed in meters per minute.”

“We have already shown with Electron that carbon composites are an ideal material for an orbital rocket,” said Beck. “Now, thanks to Neutron, it’s gonna really come into its own as a rocket material of the future.”

Back further noted that prototype tanks for Neutron’s two stages are already being built and that the first hot-fire test of the new Archimedes engine is planned for 2022. 

Notably absent from the presentation was an estimate on the first launch date, which had previously been 2024. Also absent was mention of the Mid-Atlantic Regional Spaceport in Virginia which had been planned as the initial launch site for the vehicle.

Instead, Beck mentioned a launch facility devoid of most equipment – as simple as possible.

A switch away from Pad 0A at the Mid-Atlantic Regional Spaceport would make sense given Neutron’s desire to use a very simple launch pad and its switch of propellants from RP-1 kerosene and liquid oxygen (the ground support equipment for which is already present at Pad 0A) to liquid methane and liquid oxygen.

(Lead image: Neutron on its simple launch pad. Credit: Rocket Lab)

Quelle: NS

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