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	H-I rocket
Function	Medium-lift launch vehicle
Manufacturer	Mitsubishi Heavy Industries (production); McDonnell Douglas (design);
Country of origin	Japan (production); United States (design);
Size
Height	42 m (138 ft)
Diameter	2.44 m (8 ft 0 in)
Mass	142,260 kg (313,630 lb)
Stages	2 or 3
Capacity
Payload to LEO
Mass	3,200 kg (7,100 lb)
Payload to GTO
Mass	1,100 kg (2,400 lb)
Associated rockets
Family	Thor
Based on	N-II
Derivative work	H-II
Comparable	Delta 3000, PSLV
Launch history
Status	Retired
Launch sites	Tanegashima, Osaki
Total launches	9
Success(es)	9
First flight	12 August 1986
Last flight	11 February 1992
Boosters – Castor 2
No. boosters	6 or 9
Powered by	1 × TX-354-3
Maximum thrust	258.9 kN (58,200 lbf)
Specific impulse	262 s (2.57 km/s)
Burn time	37 seconds
Propellant	HTPB/Al
First stage – Thor-ELT
Powered by	1 × MB-3-3
Maximum thrust	866.7 kN (194,800 lbf)
Specific impulse	290 s (2.8 km/s)
Burn time	270 seconds
Propellant	RP-1/LOX
Second stage
Powered by	1 × LE-5
Maximum thrust	102.9 kN (23,100 lbf)
Specific impulse	450 s (4.4 km/s)
Burn time	370 seconds
Propellant	LH2/LOX
Third stage (optional)
Powered by	1 × UM-129A
Maximum thrust	77.4 kN (17,400 lbf)
Specific impulse	291 s (2.85 km/s)
Burn time	68 seconds
Propellant	Solid
	[edit on Wikidata]

The H–I (H–1) was a Japanese medium-lift launch vehicle, 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.

Launch history

Flight No.	Date / time (UTC)	Rocket, Configuration	Launch site	Payload	Orbit	Launch outcome
15(F)	12 August 1986, 20:45	H-I	Osaki Launch Complex	EGP (Ajisai)	LEO	Success
15(F)	9 SRMs, 2 stages
17(F)	27 August 1987, 09:20	H-I	Osaki Launch Complex	ETS-5 (Kiku-5)	GTO	Success
17(F)	9 SRMs, 3 stages
18(F)	19 February 1988, 10:05	H-I	Osaki Launch Complex	CS-3A (Sakura-3A)	GTO	Success
18(F)	9 SRMs, 3 stages
19(F)	16 September 1988, 09:59	H-I	Osaki Launch Complex	CS-3B (Sakura-3B)	GTO	Success
19(F)	9 SRMs, 3 stages
20(F)	5 September 1989, 19:11	H-I	Osaki Launch Complex	GMS-4 (Himawari-4)	GTO	Success
20(F)	6 SRMs, 3 stages
21(F)	7 February 1990, 01:33	H-I	Osaki Launch Complex	MOS-1B (Momo-1B)	LEO	Success
21(F)	9 SRMs, 2 stages
22(F)	28 August 1990, 09:05	H-I	Osaki Launch Complex	BS-3A (Yuri-3A)	GTO	Success
22(F)	9 SRMs, 3 stages
23(F)	25 August 1991, 08:40	H-I	Osaki Launch Complex	BS-3B (Yuri-3B)	GTO	Success
23(F)	9 SRMs, 3 stages
24(F)	11 February 1992, 01:50	H-I	Osaki Launch Complex	JERS-1 (FUYO-1)	LEO	Success
24(F)	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]

References

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

Wade, Mark. "Delta". Encyclopedia Astronautica. Archived from the original on 17 August 2013. Retrieved 31 August 2008.
McDowell, Jonathan. "Thor". Orbital and Suborbital Launch Database. Jonathan's Space Report. Archived from the original on 1 August 2020. Retrieved 31 August 2008.
Krebs, Gunter. "H-1". Gunter's Space Page. Retrieved 31 August 2008.