Delta Cryogenic Second Stage

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Delta Cryogenic Second Stage
Second stage of a Delta IV Medium rocket.jpg
A 4-meter DCSS from a Delta IV Medium
Manufacturer Boeing IDS
United Launch Alliance
Country of origin United States
Used on Delta III
Delta IV
SLS Block I
Launch history
Status Active
Total launches 21
(stage only)
11 Delta IV 4m
7 Delta IV 5m
Failed 2 (Delta III)
Lower stage
1 (Delta III)
Delta III second stage
Length 8.8 meters (29 ft)
Diameter 4 meters (13 ft)
Empty mass 2,480 kilograms (5,470 lb)
Gross mass 19,300 kilograms (42,500 lb)
Engines 1 RL10B-2
Thrust 110.1 kilonewtons (24,800 lbf)
Specific impulse 462 seconds
Burn time 700 seconds
Fuel LH2/LOX
Delta IV 4-meter stage
Length 12.2 meters (40 ft)
Diameter 4 meters (13 ft)
Empty mass 2,850 kilograms (6,280 lb)
Gross mass 24,170 kilograms (53,290 lb)
Engines 1 RL10B-2
Thrust 110.1 kilonewtons (24,800 lbf)
Specific impulse 462 seconds
Burn time 850 seconds
Fuel LH2/LOX
Delta IV 5-meter stage
Length 13.7 meters (45 ft)
Diameter 5 meters (16 ft)
Empty mass 3,490 kilograms (7,690 lb)
Gross mass 30,710 kilograms (67,700 lb)
Engines 1 RL10B-2
Thrust 110.1 kilonewtons (24,800 lbf)
Specific impulse 462 seconds
Burn time 1125 seconds
Fuel LH2/LOX

The Delta Cryogenic Second Stage (DCSS) is a family of cryogenic rocket stages used on the Delta III & Delta IV rockets, and which is planned to be used on the Block I Space Launch System. The stage consists of a cylindrical LH2 tank structurally separated from an oblate spheroid LOX tank. The LH2 tank cylinder carries payload launch loads, while the LOX tank and engine are suspended below within the rocket's inter-stage. The stage is powered by a single Pratt & Whitney RL10B-2 engine,[1] which features an extendable carbon-carbon nozzle to improve specific impulse.[2]

Delta III[edit]

The first DCSS variant flown was on the Delta III, performing on 2 out of 3 flights. An un-flown example is on display outside the Discovery Cube Orange County.

Delta IV[edit]

On the Delta IV, depending on variant, two different versions are flown. Composite interstages used to mate the first and second stages together accommodate the different configurations.[2] For the Delta IV-M, a tapering interstage narrows down in diameter from 5-meters to 4-meters is used on the 4-meter DCSS, while a cylindrical interstage is used on the 5-meter DCSS.[2]


The Interim Cryogenic Propulsion Stage (ICPS), a modified DCSS, will be used as a second stage on the debut flight of NASA's Space Launch System,[3] Exploration Mission 1 (EM-1), scheduled for December 2019.[4]


  1. ^ Robert A. Braeunig (2 November 2009). "Space Launchers—Delta". Rocket and Space Technology ( Retrieved 26 January 2012.
  2. ^ a b c "Delta IV Payload Planners Guide" (PDF). United Launch Alliance. September 2007. pp. 1–5 to 1–6. Archived from the original (PDF) on 22 July 2011.
  3. ^ Chris Bergin (4 October 2011). "SLS trades lean towards opening with four RS-25s on the core stage". Retrieved 26 January 2012.
  4. ^ Clark, Stephen (28 April 2017). "NASA confirms first flight of Space Launch System will slip to 2019". Spaceflight Now. Retrieved 29 April 2017.