H-I

	H-I rocket
Function	Carrier rocket
Manufacturer	McDonnell Douglas (design); Mitsubishi Heavy Industries (production)
Country of origin	Japan (production); United States (design)
Size
Height	42 metres (138 ft)
Diameter	2.44 metres (8.0 ft)
Mass	142,260 kilograms (313,630 lb)
Stages	2 or 3
Capacity
Payload to LEO
Mass	3,200 kilograms (7,100 lb)
Payload to GTO
Mass	1,100 kilograms (2,400 lb)
Associated rockets
Family	Thor
Comparable	Delta 3000, PSLV
Launch history
Status	Retired
Launch sites	LA-N, Tanegashima
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 kilonewtons (58,200 lbf)
Specific impulse	262 sec
Burn time	37 seconds
Propellant	Solid
First stage – Thor-ELT
Powered by	1 MB-3-3
Maximum thrust	866.7 kilonewtons (194,800 lbf)
Specific impulse	290 sec
Burn time	270 seconds
Propellant	RP-1/LOX
Second stage
Powered by	1 LE-5
Maximum thrust	102.9 kilonewtons (23,100 lbf)
Specific impulse	450 sec
Burn time	370 seconds
Propellant	LH2/LOX
Third stage (optional)
Powered by	1 UM-129A
Maximum thrust	77.4 kilonewtons (17,400 lbf)
Specific impulse	291 sec
Burn time	68 seconds
Propellant	Solid
	[edit on Wikidata]

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.