SRB-A

  1. Home
  2. Wiki
SRB-A / SRB-3
Closeup of the SRB-A attached to the H-IIA rocket which launched the Global Precipitation Measurement spacecraft
ManufacturerIHI Corporation
Country of originJapan
Used on
SRB-A
Height14.6 m (47 ft 11 in)
Diameter2.5 m (8 ft 2 in)
Gross mass75.5 t (166,449 lb)
Propellant mass66.8 t (147,269 lb)
Maximum thrust2,300 kN (517,061 lbf)
Specific impulse283.6 s (2.781 km/s)
Burn time110 seconds
SRB-3
Height15.1 m (49 ft 6 in)
Diameter2.5 m (8 ft 2 in)
Gross mass76.6 t (168,874 lb)
Propellant mass66 t (145,505 lb)
Maximum thrust2,158 kN (485,138 lbf)[1]
Specific impulse283.6 s (2.781 km/s)[2]
Burn time116 seconds[2]

The SRB-A and SRB-3 are a family of Japanese solid-fueled rocket boosters developed and manufactured by IHI Corporation for use on the H-IIA, H-IIB, Epsilon, H3, and Epsilon S launch vehicles. The earlier versions, designated SRB-A, flew from 2001 to 2025, while the successor SRB-3 made its first flight in 2023.

Design

[edit]

All SRB variants have a composite motor case constructed from carbon-fiber-reinforced polymer materials, with thrust vector control provided by electrically actuated nozzles. IHI led development and production, with contributions from other Japanese manufacturers: the composite propellant (BP-208) was developed by NOF Corporation, and the T1000GB carbon fiber used in the motor case was developed by Toray.[3]

The SRB-A motor case incorporated foreign technology licensed from Alliant Techsystems (ATK), based on the Castor 120 motor used in the LGM-118 Peacekeeper ICBM.[4] By contrast, the SRB-3 uses a fully domestic motor case design developed in Japan.[5]

SRB-A series

[edit]

The SRB-A was developed for the H-IIA rocket and first flew in 2001. It was later used on the larger H-IIB and as the first stage of the smaller Epsilon rocket. It measured 2.5 metres (8 ft 2 in) in diameter and 15.1 metres (50 ft) in length, with a filament-wound composite casing. It replaced the SRBs used on the earlier H-II rocket.[6]

Variants

[edit]
  • SRB-A — The initial version, used on the first six H-IIA launches. A separation failure on the sixth launch in 2003 led to loss of mission.[6][7]
  • SRB-A2 — A planned upgrade canceled after the 2003 failure; its design changes were merged into the SRB-A Improved.
  • SRB-A Improved — Incorporated a redesigned bell-shaped nozzle to reduce erosion, with slightly lower thrust and longer burn time. Used on the seventh through thirteenth H-IIA flights, but nozzle erosion persisted.
  • SRB-A3 — Final SRB-A version, with further improvements to reliability and performance. Available in a high-thrust or long-burn variant. Used on all H-IIA launches after the thirteenth flight, as well as on the H-IIB and as the first stage of the Epsilon rocket.[6][8][9]

The SRB-A series was retired in 2025 and replaced by the SRB-3.

SRB-3

[edit]
Closeup of SRB-3 models attached to a model H3 rocket

The SRB-3 is the current generation of Japanese solid rocket boosters, developed for the H3 and Epsilon S launch vehicles. Compared to the SRB-A, it carries 1 tonne (2,200 lb) more propellant, uses a fixed nozzle, and incorporates a simplified separation system to reduce cost and increase reliability.[5][10]

Unlike the SRB-A series, which required different burn patterns depending on configuration and vehicle type, the SRB-3 uses a unified burn pattern whether flown in pairs or quartets on the H3, or as the first stage of the Epsilon S.[10]

References

[edit]
  1. ^ "H3 Launch Vehicle Brochure" (PDF). Archived (PDF) from the original on 11 February 2017. Retrieved 20 September 2016.
  2. ^ a b "What is SRB-3?". JAXA. Retrieved 2025-09-18.
  3. ^ "JAXA、H-IIB ロケットで宇宙ステーション補給機７号機(HTV7 「こうのとり」)を打上げ". Tokyo Express. 28 September 2018. Archived from the original on 2 October 2022. Retrieved 18 February 2023.
  4. ^ "ATK Composite Technology Supports Maiden Flight of Japan's H-IIA Space Launch Vehicle". ATK. August 29, 2001. Archived from the original on 2013-12-26.
  5. ^ a b "宇宙に吼えろ! 新型固体ロケットブースター「SRB-3」燃焼試験取材 第2回 カギは国産化と簡素化 - 先代から大きく進化を遂げた「SRB-3」". マイナビニュース. 7 September 2018. Archived from the original on 17 February 2023. Retrieved 17 February 2023.
  6. ^ a b c "SRB-A Engine Overview". JAXA. Archived from the original on November 4, 2015. Retrieved 14 February 2016.
  7. ^ Stephen Clark; Justin Ray (29 November 2003). "Japanese launch fails". Spaceflight Now. Retrieved 14 February 2016.
  8. ^ "H-IIB Launch Vehicle" (PDF). JAXA. Archived from the original (PDF) on March 26, 2014. Retrieved 14 February 2016.
  9. ^ "Epsilon Launch Vehicle" (PDF). JAXA. Retrieved 14 February 2016.
  10. ^ a b "H3プロジェクト前進へ" (PDF). 宇宙航空の最新情報マガジン JAXA's. 74. JAXA: 10. 1 October 2018. Archived from the original (PDF) on 18 March 2022. Retrieved 17 February 2023.