Delta Cryogenic Second Stage


Delta Cryogenic Second Stage
Second stage of a Delta IV Medium rocket.jpg
A 4-meter DCSS from a Delta IV Medium
ManufacturerBoeing IDS
United Launch Alliance
Mitsubishi Heavy Industries
(Original Delta III design and manufacturing)
Country of originUnited States
Used onDelta III
Delta IV
SLS Block I
Launch history
Total launches21
(stage only)
11 Delta IV 4 m
7 Delta IV 5 m
Failed2 (Delta III)
Lower stage
1 (Delta III)
Delta III second stage
Length8.8 meters (29 ft)
Diameter4 meters (13 ft)
Empty mass2,480 kilograms (5,470 lb)
Gross mass19,300 kilograms (42,500 lb)
Engines1 RL10B-2
Thrust110.1 kilonewtons (24,800 lbf)
Specific impulse462 seconds (4.53 km/s)
Burn time700 seconds
Delta IV 4-meter stage
Length12.2 meters (40 ft)
Diameter4 meters (13 ft)
Empty mass2,850 kilograms (6,280 lb)
Gross mass24,170 kilograms (53,290 lb)
Engines1 RL10B-2
Thrust110.1 kilonewtons (24,800 lbf)
Specific impulse462 seconds (4.53 km/s)
Burn time850 seconds
Delta IV 5-meter stage
Length13.7 meters (45 ft)
Diameter5 meters (16 ft)
Empty mass3,490 kilograms (7,690 lb)
Gross mass30,710 kilograms (67,700 lb)
Engines1 RL10B-2
Thrust110.1 kilonewtons (24,800 lbf)
Specific impulse462 seconds (4.53 km/s)
Burn time1125 seconds

The Delta Cryogenic Second Stage (DCSS) is a family of cryogenic rocket stages used on the Delta III and Delta IV rockets, and which is planned to be used on the Space Launch System Block 1. The stage consists of a cylindrical liquid hydrogen (LH2) tank structurally separated from an oblate spheroid liquid oxygen (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 Aerojet Rocketdyne-Pratt & Whitney RL10B-2 engine,[1] which features an extendable carbon-carbon nozzle to improve specific impulse.[2]

Delta III

The DCSS first flew on 3 Delta IIIs, and failed 2 of 2 times. The booster failed on the third flight, causing the loss of the DCSS before ignitions. An un-flown example is on display outside the Discovery Cube Orange County.[citation needed]

Delta IV

Two different versions are flown, depending on variant. Composite interstages used to mate the first and second stages together accommodate the different configurations.[2] For the Delta IV-M, a tapering interstage that 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]

Interim Cryogenic Propulsion Stage

The Interim Cryogenic Propulsion Stage, a minimally modified 5-meter DCSS, is used as the upper stage of the Space Launch System Block 1. The ICPS was mated to the SLS launch stack on July 6, 2021.[3][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. ^ Rosenberg, Zach. "Delta second stage chosen as SLS interim". Flight International, May 8, 2012.