Article · Wikipedia archive · Last revised Jul 23, 2026

N-I (rocket)

The N-I or N-1 was a derivative of the American Thor-Delta rocket produced under license in Japan. The "N" stood for "Nippon" (Japan). The vehicle used a Long Tank Thor first stage derived from the PGM-17 Thor intermediate-range ballistic missile, a Mitsubishi Heavy Industries-designed LE-3 engine on the second stage, and three Castor 2 solid rocket motors. An optional third stage, the Star-37N solid motor, was used on three of the seven launches.

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N-I
The N-I rocket1
FunctionSmall-lift launch vehicle
ManufacturerMcDonnell Douglas (design)
Mitsubishi Heavy Industries (production)
Country of originUnited States (design)
Japan (production)
Size
Height34 m (112 ft)1
Diameter2.44 m (8.0 ft)
Mass131,330 kg (289,530 lb)1
Stages2 or 3
Capacity
Payload to LEO
Mass1,200 kg (2,600 lb)1
Payload to GTO
Mass360 kg (790 lb)1
Associated rockets
FamilyDelta
Derivative workN-II
Launch history
StatusRetired
Launch sitesTanegashima, Osaki
Total launches7
Success(es)6
Failure1
First flight9 September 1975
Last flight3 September 1982
Boosters – Castor 2
No. boosters32
Maximum thrust258.9 kN (58,200 lbf) each
Total thrust776.7 kN (174,600 lbf)
Specific impulse262 s (2.57 km/s)
Burn time37 seconds
PropellantSolid
First stage – Thor-ELT
Powered by1 × MB-3-3
Maximum thrust866.7 kN (194,800 lbf)
Specific impulse290 s (2.8 km/s)
Burn time270 seconds
PropellantRP-1 / LOX
Second stage
Powered by1 × LE-3
Maximum thrust52.9 kN (11,900 lbf)
Specific impulse290 s (2.8 km/s)
Burn time246 seconds
PropellantN2O4 / A-50
Third stage (optional) – Star-37N
Maximum thrust45 kN (10,000 lbf)
Specific impulse290 s (2.8 km/s)
Burn time42 seconds
PropellantSolid

The N-I or N-1 was a derivative of the American Thor-Delta rocket produced under license in Japan. The "N" stood for "Nippon" (Japan). The vehicle used a Long Tank Thor first stage derived from the PGM-17 Thor intermediate-range ballistic missile, a Mitsubishi Heavy Industries-designed LE-3 engine on the second stage,345 and three Castor 2 solid rocket motors. An optional third stage, the Star-37N solid motor, was used on three of the seven launches.

Seven N-I rockets were launched between 1975 and 1982, after which the vehicle was replaced by the N-II. Six launches were successful. The fifth flight failed after the payload and third stage collided shortly after separation.

On 29 February 1976, the second N-I launch conducted the only orbital launch on a leap day, as of February 2024.6

Launch history

Mock up of N-1 source ↗
Flight Date (UTC) Launch site Payload7 Payload mass Orbit Outcome
F1 9 September 1975
05:308 		Tanegashima, Osaki ETS-I 82.5 kg (182 lb)9 LEO Success
ETS-I (Engineering Test Satellite I, nicknamed Kiku-1) was the first satellite launched by the NASDA. It had the objective of acquiring information on N-series launch vehicles, orbit injection, and tracking and control.9 It ceased operations on 28 April 1982.
F2 29 February 1976
03:308 		Tanegashima, Osaki ISS 139 kg (306 lb)10 LEO Success
ISS (Ionosphere Sounding Satellite, nicknamed UME) was used to monitor radio waves in the ionosphere and forecast conditions for shortwave communications.10 A power supply issue caused Ume to stop functioning one month after launch.11
F3 23 February 1977
08:508 		Tanegashima, Osaki ETS-II 130 kg (290 lb)12 GTO Success
3rd stage used. ETS-II (Engineering Test Satellite II, nicknamed Kiku-2) was NASDA's first satellite launched to GEO.12 It was intended to gather data on geostationary satellite launch, tracking, control, orbit maintenance, and attitude control as well as carrying out experiments on communications equipment. Kiku-2 ceased operations on 10 December 1990, leaving GEO.
F4 16 February 1978
04:008 		Tanegashima, Osaki ISS-b 141 kg (311 lb)10 LEO Success
ISS-b (Ionosphere Sounding Satellite b, nicknamed UME-2) had similar goals to the original UME satellite, but was much more successful in carrying them out. While it was originally intended to gather data for only a year and a half, UME-2 ceased operations on 23 February 1983.
F5 6 February 1979
08:468 		Tanegashima, Osaki ECS 130 kg (290 lb)13 GTO Failure
3rd stage used. ECS (Experimental Communications Satellite, nicknamed Ayame). Satellite and third stage collided shortly after separation.13 The satellite had the intention of conducting millimeter wave experiments.
F6 22 February 1980
08:358 		Tanegashima, Osaki ECS-b 130 kg (290 lb)13 GTO Success
3rd stage used. ECS-b (Experimental Communications Satellite b, nicknamed Ayame-2). Repeat of the ECS mission. Satellite stopped transmitting shortly after separation.
F9a 3 September 1982
05:008 		Tanegashima, Osaki ETS-III 385 kg (849 lb)14 LEO Success
ETS-III (Engineering Test Satellite III, nicknamed Kiku-4) was developed to acquire data on designing earth observation satellites with high power requirements.14 ETS-III completed testing of three-axis attitude control, deployable solar panels, movable heat control, and ion engine operation. On 8 April 1985, the satellite ran out of fuel and ceased operation.
  1. Flights 7 and 8 used the N-II rocket
See also

See also

References

References

  1. Wade, Mark. "Delta". Encyclopedia Astronautica. Archived from the original on 17 August 2013. Retrieved 3 September 2008.
  2. "JAXA Digital Archives". Japan Aerospace Exploration Agency. Archived from the original on 9 September 2009. Retrieved 1 October 2009.
  3. Takenaka, Yukihiko. "N-Iロケット開発の歩み" [The Development History of the N-I Rocket] (in Japanese). NASDA. Retrieved 10 February 2011.
  4. "三菱重工 名古屋誘導推進システム製作所 事業所紹介 沿革" [Mitsubishi Heavy Industries, Ltd. — Nagoya Guidance & Propulsion Systems Works: Site Overview — History] (in Japanese). Mitsubishi Heavy Industries. Archived from the original on 4 July 2011. Retrieved 10 February 2011.
  5. "第1部 創造性豊かな科学技術を求めて 第2章 自主技術開発への展開 第3節 先導的・基盤的科学技術分野における自主技術開発の展開 2.宇宙開発" [Part 1: In Pursuit of Creative Science and Technology — Chapter 2: Advancing Independent Technology Development — Section 3: The Development of Independent Technology in Leading and Fundamental Scientific and Technological Fields — 2. Space Development] (in Japanese). Ministry of Education, Culture, Sports, Science and Technology. Archived from the original on 15 June 2008. Retrieved 10 February 2011.
  6. Pearlman, Robert (29 February 2016). "Space Station Command Change Is One Giant Leap (Day) for Space History". Space.com. Retrieved 2 November 2017.
  7. "N-I Launch Vehicle". JAXA | Japan Aerospace Exploration Agency. Retrieved 18 February 2024.
  8. McDowell, Jonathan. "Thor". Orbital and Suborbital Launch Database. Jonathan's Space Report. Archived from the original on 1 August 2020. Retrieved 31 August 2008.
  9. "Engineering Test Satellite I "KIKU-1" (ETS-I)". JAXA | Japan Aerospace Exploration Agency. Retrieved 18 February 2024.
  10. "Ionosphere Sounding Satellite "UME" (ISS)". JAXA | Japan Aerospace Exploration Agency. Retrieved 18 February 2024.
  11. "ISS a, b (Ume 1, 2)". Gunter's Space Page. Retrieved 18 February 2024.
  12. "Engineering Test Satellite II "KIKU-2" (ETS-II)". JAXA | Japan Aerospace Exploration Agency. Retrieved 18 February 2024.
  13. "Experimental Communications Satellites "Ayame" (ECS)". JAXA | Japan Aerospace Exploration Agency. Retrieved 18 February 2024.
  14. "Engineering Test Satellite III "KIKU-4" (ETS-III)". JAXA | Japan Aerospace Exploration Agency. Retrieved 18 February 2024.