H-I rocket
FunctionCarrier rocket
ManufacturerMcDonnell Douglas (design)
Mitsubishi Heavy Industries (production)
Country of originJapan (production)
United States (design)
Height42 metres (138 ft)
Diameter2.44 metres (8.0 ft)
Mass142,260 kilograms (313,630 lb)
Stages2 or 3
Payload to LEO
Mass3,200 kilograms (7,100 lb)
Payload to GTO
Mass1,100 kilograms (2,400 lb)
Associated rockets
ComparableDelta 3000, PSLV
Launch history
Launch sitesLA-N, Tanegashima
Total launches9
First flight12 August 1986
Last flight11 February 1992
Boosters – Castor 2
No. boosters6 or 9
Powered by1 TX-354-3
Maximum thrust258.9 kilonewtons (58,200 lbf)
Specific impulse262 sec
Burn time37 seconds
First stage – Thor-ELT
Powered by1 MB-3-3
Maximum thrust866.7 kilonewtons (194,800 lbf)
Specific impulse290 sec
Burn time270 seconds
Second stage
Powered by1 LE-5
Maximum thrust102.9 kilonewtons (23,100 lbf)
Specific impulse450 sec
Burn time370 seconds
Third stage (optional)
Powered by1 UM-129A
Maximum thrust77.4 kilonewtons (17,400 lbf)
Specific impulse291 sec
Burn time68 seconds

The H–I or H–1 was a Japanese liquid-fuelled carrier rocket, consisting of a licence-produced American first stage and set of booster rockets, and all-Japanese upper stages. The H in the name represented the use of liquid hydrogen fuel in the second stage. It was launched nine times between 1986 and 1992. It replaced the N-II, and was subsequently replaced by the H-II, which used the same upper stages with a Japanese first stage.

The first stage of the H–I was a licence-built version of the Thor-ELT, which was originally constructed for the US Delta 1000 rocket. The stage had already been produced under licence in Japan for the N-I and N-II rockets. The second stage was entirely Japanese, using an LE-5 engine, the first rocket engine in Japan to use a cryogenic fuel. On launches to Geosynchronous transfer orbits, a Nissan–built UM-69A solid motor was used as a third stage. Depending on the mass of the payload, either six or nine US Castor 2 SRMs were used as booster rockets.

The American Thor-ELT was used for the H-I.

Launch history

Flight No. Date / time (UTC) Rocket,
Launch site Payload Payload mass Orbit Customer Launch
15(F) 12 August 1986,
H-I Osaki Launch Complex EGP (Ajisai) LEO Success
9 SRMs, 2 stages
17(F) 27 August 1987,
H-I Osaki Launch Complex ETS-5 (Kiku-5) GTO Success
9 SRMs, 3 stages
18(F) 19 February 1988,
H-I Osaki Launch Complex CS-3A (Sakura-3A) GTO Success
9 SRMs, 3 stages
19(F) 16 September 1988,
H-I Osaki Launch Complex CS-3B (Sakura-3B) GTO Success
9 SRMs, 3 stages
20(F) 5 September 1989,
H-I Osaki Launch Complex GMS-4 (Himawari-4) GTO Success
6 SRMs, 3 stages
21(F) 7 February 1990,
H-I Osaki Launch Complex MOS-1B (Momo-1B) LEO Success
9 SRMs, 2 stages
22(F) 28 August 1990,
H-I Osaki Launch Complex BS-3A (Yuri-3A) GTO Success
9 SRMs, 3 stages
23(F) 25 August 1991,
H-I Osaki Launch Complex BS-3B (Yuri-3B) GTO Success
9 SRMs, 3 stages
24(F) 11 February 1992,
H-I Osaki Launch Complex JERS-1 (FUYO-1) LEO Success
9 SRMs, 2 stages

When the H–1 was announced in 1986, company representative Tsuguo Tatakawe clarified that it would only be used to launch indigenous (i.e. Japanese) payloads, that only two launches per year could be mounted, and that the launch window consisted of a four-month period in which Japanese fishing fleets were not active (the falling launch boosters may damage fishing nets in the ocean waters).[1]

See also


  1. ^ Japan's H–1 and H–2 rockets, Air & Space/Smithsonian, February/March 1987, p. 19