Space Launch System - SLS
The imaginatively named Space Launch System, or SLS [also called the Senate Launch System, in tribute to the projects political support], is an undertaking to sustain the industrial base created in the Space Shuttle Program. The booster utilizes hardware initially developed for the Space Shuttle, less the Orbiter. Preservation of this industrial base does not actually require flying the rocket, and indeed this mighty rocket has proven remarkably Earth-bound, with a schedule that slips roughly year every year.
The SLO is intended to provide an entirely new capability for human exploration beyond Earth orbit. It also might back up commercial and international partner transportation services to the International Space Station. Designed to be flexible for crew or cargo missions, the SLS is intended to be safe, affordable, and sustainable, to continue America's journey of discovery from the unique vantage point of space. The SLS will take astronauts farther into space than ever before, while engaging the US aerospace workforce here at on Earth.
The Space Launch System, or SLS, would carry the Orion Multi-Purpose Crew Vehicle, as well as cargo, equipment and science experiments, to deep space. The Orion spacecraft would carry up to four astronauts beyond low Earth orbit on long-duration, deep space missions and include both crew and service modules and a launch abort system to significantly increase crew safety. As NASA’s commercial partners create an American supply line to the International Space Station, SLS will provide the transportation needed for NASA to reach further into our solar system. However, if needed, SLS could support backup transportation to the International Space Station.
SLS will be the most powerful rocket in history and is designed to be flexible and evolvable, to meet a variety of crew and cargo mission needs. The SLS will be NASA’s first exploration-class vehicle since the Saturn V took American astronauts to the moon over 40 years ago. With its superior lift capability, the SLS will expand our reach in the solar system, allowing astronauts aboard the Orion spacecraft to explore multiple, deep-space destinations including near-Earth asteroids, Lagrange points, the moon and ultimately Mars. The SLS heavy-lift launch vehicle is essential to NASA’s deep-space exploration endeavors. The system will be flexible and include multiple launch vehicle configurations. The SLS will carry crew, cargo and science missions to deep space.
The SLS will use proven hardware and cutting-edge tooling and manufacturing technology from the Space Shuttle and other exploration programs. This will significantly reduce development and operations costs. It will use a liquid hydrogen and liquid oxygen propulsion system, which will include the RS-25 engine from the Space Shuttle Program for the core stage and the J-2X engine for the upper stage. The SLS also will use solid rocket boosters for the initial development flights.
The 70-metric-ton- (77 ton) configuration will lift more than 154,000 pounds and will provide 10 percent more thrust than the Saturn V rocket while the 130-metric-ton-(143 ton) configuration will lift more than 286,000 pounds and provide 20 percent more thrust than the Saturn V. The 70-metric-ton SLS will stand 321 feet tall, provide 8.4 million pounds of thrust at liftoff, weigh 5.5 million pounds and carry 154,000 pounds of payload.
The Boeing Co. of Huntsville, AL, is developing the SLS core stage, including its avionics. Towering over 200 feet tall with a diameter of 27.5 feet, the core stage will store cryogenic liquid hydrogen and liquid oxygen that will feed the RS-25 engines for the SLS. The stage is being built at NASA’s Michoud Assembly Facility in New Orleans with state-of-the-art manufacturing equipment. Flight computer hardware and battery unit development are under way. The SLS core stage will get its power from four RS-25 engines — former space shuttle main engines built by Pratt & Whitney Rocketdyne of Canoga Park, Calif. The SLS Program has an inventory of 15 RS-25 flight engines, which operated with 100 percent mission success during 135 space shuttle missions.
A pair of five-segment solid rocket boosters would be used for the first two, 70-metric-ton-flights of the SLS. The prime contractor for the boosters — ATK of Brigham City, Utah — began processing its first SLS hardware components in preparation for the initial qualification test planned for spring 2013.
An interim cryogenic propulsion stage would be used on the first two flights of the SLS, based on Boeing’s Delta Cryogenic Second Stage used on the Delta IV family of launch vehicles. The interim cryogenic propulsion stage will boost the Orion spacecraft to the correct altitude and trajectory needed to send the spacecraft around the moon in order to check out vital systems during the initial test flights. The 130-metric-ton-SLS will include an upper stage to provide additional power needed to travel to deep space. The upper stage, built by Boeing, will share common attributes with the core stage such as its outer diameter, material composition, subsystem components and tooling to save cost and design time.
The first SLS mission — Exploration Mission 1 — will launch an Orion spacecraft with no crew to demonstrate the integrated system performance of the SLS rocket and spacecraft prior to a crewed flight. The second SLS mission, Exploration Mission 2, was targeted for 2021 and would launch Orion and a crew of up to four American astronauts.
NASA Associate Administrator for Human Exploration and Operations William Gerstenmaier said 10 December 2014 that NASA pushed back its Space Launch System (SLS) first launch goal to roughly June 2018 from its previous estimate of December 2017.
In 2016, NASA negotiated an increase in the value of the Boeing Stages contract of approximately $1 billion to account for delays experienced up to May 2016. In 2017, NASA negotiated additional requirements, increasing the contract’s value by another $1 billion for development and production of an Exploration Upper Stage (EUS), a new and more powerful second stage designed to increase the SLS’s upmass capability.
Boeing officials consistently underestimated the scope of the work to be performed and thus the size and skills of the workforce required to perform specialized work such as electrical tasks and building the rocket’s Thermal Protection System.28 For example, when Boeing realized that it needed a larger workforce to build the Core Stage, the contractor had difficulty attracting qualified technical and support employees, preventing it from quickly adding additional personnel. In May 2018, the Defense Contract Management Agency reported that Boeing’s estimated costs to complete work on the two Core Stages and the EUS were unrealistic and overly optimistic due to inaccurate and incomplete information in Boeing’s Earned Value Management System.
A NASA Office of Inspector General report issued October 10, 2018 reported "Originally, the first uncrewed mission of the combined SLS/Orion system known as Exploration Mission-1 (EM-1) had a launch readiness date of December 2017, while the first crewed mission of the system known as Exploration Mission-2 (EM-2) was projected to launch in mid-2021. However, due to continued production delays with the SLS Core Stage and upcoming critical testing and integration activities, current NASA schedules indicate launch dates of mid-2020 and mid-2022, respectively. With $5.3 billion expended as of August 2018 out of $6.2 billion allocated for the Boeing Stages contract, NASA expects Boeing to reach the contract’s value by early 2019—nearly 3 years before the contract is supposed to end—without final delivery of a single Core Stage or EUS.... we project Boeing will expend at least $8.9 billion through 2021 — double the amount initially planned..."
The first launch has slipped from 2017 to at least 2020 over the course of its development. NASA originally planned to shift to the Block 1B with the Exploration Upper Stage (EUS) on the second SLS flight, the agency instead expects to fly the original Block 1 version, with its Interim Cryogenic Propulsion Stage, for at least three missions.
Space News reported March 2019 that the director of NASA’s Marshall Space Flight Center said 05 March 2019 that the agency is “reassessing” the 2020 launch date for the first flight of its Space Launch System, suggesting that the mission may face further delays. Singer said the launch readiness date for Exploration Mission (EM) 1 is still in 2020, but did not give a more precise estimate of the date even as NASA reviews possible changes to it. “We do know that we are reassessing those dates to see if that date will work, based on making sure we have the vehicle ready, and ready to go fly safely,” she said. “We are assessing that date. Our launch readiness date is still 2020, and we’re doing everything within our power to make sure that we support that.”
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