The Delta Cryogenic Second Stage (DCSS) is a family of cryogenic-fuelled rocket stages used on the

Delta III Delta III was an expendable launch vehicle made by McDonnell Douglas (later acquired by Boeing). Development was canceled before the vehicle became operational. The vehicle is the third generation of the Delta rocket family, developed from the ...

Delta IV Delta IV was a group of five expendable launch systems in the Delta rocket family. It flew 45 missions from 2002 to 2024. Originally designed by Boeing's Defense, Space and Security division for the Evolved Expendable Launch Vehicle (EELV) p ...

, and on the

Space Launch System The Space Launch System (SLS) is an American Super heavy-lift launch vehicle, super heavy-lift Expendable launch system, expendable launch vehicle used by NASA. As the primary launch vehicle of the Artemis program, Artemis Moon landing progra ...

Block 1 launch vehicles. The DCSS employs a unique two-tank architecture where the cylindrical

liquid hydrogen Liquid hydrogen () is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecule, molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point (thermodynamics), critical point of 33 Kelvins, ...

(LH₂) tank carries payload launch loads and forms the upper section. An

oblate spheroid A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circu ...

tank filled with

liquid oxygen Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...

(LOX) and the engine are suspended from the LH₂ tank and covered by the interstage during initial launch. The DCSS is powered by a single RL10B-2 engine built by

Aerojet Rocketdyne Aerojet Rocketdyne is a subsidiary of American Arms industry, defense company L3Harris that manufactures rocket, Hypersonic flight, hypersonic, and electric propulsive systems for space, defense, civil and commercial applications. Aerojet traces ...

, which features an extendable carbon–carbon nozzle to improve specific impulse. The DCSS was designed by the

National Space Development Agency of Japan The , or NASDA, was a Japanese national space agency established on October 1, 1969 under the National Space Development Agency Law only for peaceful purposes. Based on the Space Development Program enacted by the Minister of Education, Culture ...

, based on the second stage it developed for the

H-IIA H-IIA (H-2A) is an active expendable launch system operated by Mitsubishi Heavy Industries (MHI) for the Japan Aerospace Exploration Agency. These liquid fuel rockets have been used to launch satellites into geostationary orbit; lunar orbi ...

rocket. The initial versions for the Delta III were built by

Mitsubishi Heavy Industries is a Japanese Multinational corporation, multinational engineering, electrical equipment and electronics corporation headquartered in Tokyo, Japan. MHI is one of the core companies of the Mitsubishi Group and its automobile division is the prede ...

in Japan. For the Delta IV, production was transferred to

Boeing Integrated Defense Systems Boeing Defense, Space & Security (BDS) is a division of the Boeing Company based in Arlington, Virginia, near Washington, D.C. The division builds military airplanes, rotorcraft, and missiles, as well as space systems for both commercial and mili ...

and later to

United Launch Alliance United Launch Alliance, LLC (ULA) is an American launch service provider formed in December 2006 as a joint venture between Lockheed Martin Space and Boeing Defense, Space & Security. The company designs, assembles, sells and launches rockets ...

Delta III

The DCSS first flew on three

missions, however it was never successful. On its maiden flight, a booster failed and the rocket was destroyed by range safety, causing the loss of the DCSS before ignition. The second mission saw the DCSS itself malfunction tumbling uncontrollably, inserting the payload into a useless orbit. On the third flight, the DCSS performed its planned burn but fell short of the target orbit due to premature propellant exhaustion, resulting in mission failure. An un-flown example is on display outside the Discovery Cube Orange County. Delta III second stage

Delta IV

The

launch vehicle utilized two distinct versions of the Delta Cryogenic Second Stage (DCSS) to cater to the specific launch needs. These variants are the original DCSS with a diameter that is largely identical to the version used on the Delta III and the larger version with a diameter used to lift larger payloads. These variations necessitated the use of composite interstages, which linked the first and second stages together. For the Delta IV Medium configuration, a tapering interstage was employed to transition between the 5-meter diameter of the first stage and the smaller 4-meter diameter of the DCSS. In contrast, the

Delta IV Heavy The Delta IV Heavy (Delta 9250H) was an expendable heavy-lift launch vehicle, the largest type of the Delta IV family. It had the highest capacity of any operational launch vehicle in the world after the retirement of the Space Shuttle in 20 ...

configuration and some Delta IV Medium+ configurations, with larger payload capacities, utilized a cylindrical interstage that matched the diameter of its 5-meter DCSS. The Delta IV family of rockets has been retired, with a final launch on 9 April 2024.

Interim Cryogenic Propulsion Stage

The Interim Cryogenic Propulsion Stage (ICPS) serves as the upper stage for the initial configuration (Block 1) of NASA's

(SLS). It's a derivative of the 5-meter DCSS, with minimal modifications for SLS integration. Like the earlier DCSS, the ICPS is powered by one Aerojet Rocketdyne

RL10 The RL10 is a liquid-fuel cryogenic rocket engine built in the United States by Aerojet Rocketdyne that burns cryogenic liquid hydrogen and liquid oxygen propellants. Modern versions produce up to of thrust per engine in vacuum. RL10 version ...

engine and generates of maximum thrust. Like all previous DCSS units, Artemis I used the RL10B-2 engine, however Artemis II and III will use the RL10C-2. The ICPS for the

Artemis I Artemis I, formerly Exploration Mission-1 (EM-1), was an uncrewed Lunar orbit, Moon-orbiting mission that was launched in November 2022. As the first major spaceflight of NASA's Artemis program, Artemis I marked the agency's return to lunar e ...

mission was mated to the SLS launch stack on 6 July 2021.Rosenberg, Zach
"Delta second stage chosen as SLS interim"
''Flight International'', 8 May 2012. It performed as expected, providing the necessary thrust during the successful launch on 16 November 2022 at 06:47:44 UTC (01:47:44 EST). The ICPS is designed as a temporary solution and slated to be replaced by the next-generation

Exploration Upper Stage The Exploration Upper Stage (EUS) is a rocket stage under development for future flights of NASA’s Space Launch System (SLS). Designed for use on the SLS Block 1B and Block 2 configurations, it will replace the Interim Cryogenic Propulsion ...

for the

Artemis IV Artemis IV is a planned mission of the NASA-led Artemis program. The mission is proposed to include the fourth use of a Space Launch System (SLS) launch vehicle, sending an Orion spacecraft with four astronauts to the Lunar Gateway space statio ...

mission and beyond.

References

External links

Official ULAlaunch ICPS Photo album
{{Upper stages Cryogenic Second Stage Space Launch System United Launch Alliance Rocket engines using hydrogen propellant Rocket stages Boeing spacecraft and space launch systems