# 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). It used a Long Tank Thor first stage, a Mitsubishi Heavy Industries-designed LE-3 engine on the second stage, and three Castor SRMs. Seven were launched between 1975 and 1982, before it was replaced by the N-II. Six of the seven launches were successful, however on the fifth flight, there was recontact between the satellite and the third stage, which caused the satellite to fail.
On 29 February 1976, the second N-I conducted the only orbital launch, as of 17 February 2024, to occur on a leap day.

## Launch history

| Flight No. | Date / time (UTC) | Launch site | Payload | Payload mass | Orbit | Launch outcome |
| 1(F) | 9 September 1975 05:30 | Tanegashima | Engineering Test Satellite I "KIKU-1"(ETS-I) | 82.5kg | LEO | Success |
| 2(F) | 29 February 1976 03:30 | Tanegashima | Ionosphere Sounding Satellite "UME"(ISS) | 139kg | LEO | Success |
| 3(F) | 23 February 1977 08:50 | Tanegashima | Engineering Test Satellite II "KIKU-2"(ETS-II) | 130kg | GTO | Success |
| 3rd stage used ||||||
| 4(F) | 16 February 1978 04:00 | Tanegashima | Ionosphere Sounding Satellite "UME-2"(ISS-b) | 141kg | LEO | Success |
| 5(F) | 6 February 1979 08:46 | Tanegashima | Experimental Communications Satellites "Ayame"(ECS) | 130kg | GTO | Partial failure |
| 3rd stage used; Recontact between satellite and upper stage. ||||||
| 6(F) | 22 February 1980 08:35 | Tanegashima | Experimental Communications Satellites "Ayame-2"(ECS-b) | 130kg | GTO | Success |
| 3rd stage used; Satellite failed shortly after separation. ||||||
| 9(F) | 3 September 1982 05:00 | Tanegashima | Engineering Test Satellite III "KIKU-4"(ETS-III) | 385kg | LEO | Success |

## Payload Descriptions
### Engineering Test Satellite I "KIKU-1" (ETS-1)

ETS-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. It ceased operations on 28 April 1982.

### Ionosphere Sounding Satellite "UME" (ISS)

UME was Japan's first Ionosphere Sounding Satellite. It was used to monitor radio waves in the ionosphere and forecast conditions for shortwave communications. A power supply issue caused Ume to stop functioning one month after launch.

### Engineering Test Satellite II "KIKU-2" (ETS-2)

KIKU-2 was NASDA's first satellite launched to GEO. 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.

### Ionosphere Sounding Satellite "UME-2" (ISS-b)

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.

### Experimental Communications Satellites "Ayame/Ayame-2" (ECS/ECS-b)

Both ECS satellites were unsuccessful in completing their mission. During the first ECS launch, the third stage rocket collided with the satellite shortly after separation. During the ECS-2 launch, the satellite stopped transmitting shortly after separation. The satellites had the intention of conducting millimeter wave experiments. The JAXA website states that "we learned some valuable lessons on satellite separation technology and apogee engine from this experience".

### About Engineering Test Satellite III "KIKU-4" (ETS-III)

KIKU-4 was developed to acquire data on designing earth observation satellites with high power requirements. KIKU-4 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.