Vostok spacecraft replica.jpg
Vostok spacecraft replica at the Technik Museum Speyer, Germany. The lower conical section was the service module with the S5.4/TDU-1 engine.
Country of originUSSR
First flight1959
DesignerOKB-2, A.M. Isaev
ApplicationSpacecraft breaking engine
Liquid-fuel engine
PropellantAK20F / TG-02
Mixture ratio3.07
CycleGas Generator
Chamber1 main + 4 vernier
Thrust (vac.)15.83 kilonewtons (3,560 lbf)
Chamber pressure5.6 megapascals (810 psi)
Isp (vac.)266 seconds
Burn time45 seconds
Propellant capacity250 kilograms (550 lb)
Length1.13 metres (44 in)
Diameter0.95 metres (37 in)
Dry weight98 kilograms (216 lb)
Used in
Vostok, Voskhod and Zenit

The S5.4 (AKA TDU-1, GRAU Index 8D66), was a Russian liquid rocket engine burning TG-02 and AK20F in the gas generator cycle. It was originally used as the braking (deorbit) engine of the Vostok, Voskhod, and Zenit spacecraft, which later switched to solid engines.[citation needed]

The engine produced 15.83 kilonewtons (3,560 lbf) of thrust with a specific impulse of 266 seconds in vacuum, and burned for 45 seconds, enough for the deorbit. It had a main fixed combustion chamber and four small verniers to supply vector control. It was housed in the service module and had two toroidal tanks for pressurization.[4][5][6]

It was designed by OKB-2, the Design Bureau led by Aleksei Isaev, for the Vostok program. The braking engine for the first manned spacecraft was a difficult task that no design bureau wanted to take.[citation needed] It was considered critical, as a failure would have left a cosmonaut stranded in space. A solid engine was considered, but the ballistic experts predicted a 500-kilometer (270-nautical-mile) landing error, versus a tenth of that for a liquid engine. It took the coordinated efforts of Boris Chertok and Sergei Korolev to convince Isaev to accept the task.[7]


  1. ^ Brügge, Norbert. "Spacecraft-propulsion blocks (KDU) from Isayev's design bureau (now Khimmash)". B14643.de. Archived from the original on 2015-06-02. Retrieved 2015-06-02.
  2. ^ "S5.4". Encyclopedia Astronautica. Retrieved 2015-07-25.
  3. ^ Pillet, Nicolas. "Le vaisseau Vostok" [The Vostk spacecraft] (in French). Kosmonavtika.com. Retrieved 2015-07-25.
  4. ^ Zak, Anatoly. "Origin of the Vostok spacecraft". RussianSpaceWeb. Retrieved 2015-07-25.
  5. ^ LePage, Andrew J. "Vostok: an aerospace classic". The Space Review. Retrieved 2015-07-15.
  6. ^ Turner, Martin J. L. (2008). "Section 9.2 — Crewed launchers and re-entry vehicles". Rocket and Spacecraft Propulsion: Principles, Practice and New Developments. Springer Science & Business Media. p. 314. ISBN 978-3540692034. Retrieved 2015-07-15.
  7. ^ Chertok, Boris (May 2009). "Chapter 2 — Preparation for Piloted Flights". Rockets and People Vol. 3 — Hot Days of the Cold War (PDF). Volume 3 (NASA SP-2006-4110). NASA. p. 26. ISBN 978-0-16-081733-5. Retrieved 2015-07-15.

External links

  • KB KhIMMASH Official Page (in Russian)