Epsilon (rocket)

The Epsilon Launch Vehicle, or Epsilon rocket (イプシロンロケット, Ipushiron roketto) (formerly Advanced Solid Rocket), is a Japanese solid-fuel rocket designed to launch scientific satellites. It is a follow-on project to the larger and more expensive M-V rocket which was retired in 2006. The Japan Aerospace Exploration Agency (JAXA) began developing the Epsilon in 2007. It is capable of placing a 590 kg payload into Sun-synchronous orbit.^[7]

Epsilon

Epsilon flight F2 before launch in December 2016
Function	Launch vehicle
Country of origin	Japan
Cost per launch	US$39 million[1]
Size
Height	24.4 m (Demonstration Flight) 26 m (Enhanced) 27.2 m (Epsilon S)[2]
Diameter	2.5 m
Mass	91 t (Demonstration Flight) 95.4 t (Enhanced) ~100 t (Epsilon S)
Stages	3–4
Capacity
Payload to 250 x 500 km orbit Standard 3 stages configuration
Mass	1,500 kg (3,300 lb)
Payload to 500 km orbit Optional 4 stages configuration
Mass	700 kg (1,500 lb)
Payload to 500 km orbit Epsilon S
Mass	1,400 kg (3,100 lb)[2]
Payload to 500 km SSO Optional 4 stages configuration
Mass	590 kg (1,300 lb)
Payload to 700 km SSO Epsilon S
Mass	600 kg (1,300 lb)[2]
Launch history
Status	Active
Launch sites	Uchinoura
Total launches	6
Success(es)	5
Failure(s)	1
Partial failure(s)	0
First flight	14 September 2013
Last flight	12 October 2022
First stage (Demonstration Flight/Enhanced) – SRB-A3
Powered by	1 solid
Maximum thrust	2,271 kN (511,000 lbf)[3]
Specific impulse	284 s (2.79 km/s)
Burn time	116 seconds
First stage (Epsilon S) – SRB-3
Powered by	1 solid
Maximum thrust	2,158 kN (485,000 lbf)[4]
Specific impulse	283.6 s (2.781 km/s)
Burn time	105 seconds
Second stage (Demonstration Flight) – M-34c
Powered by	1 solid
Maximum thrust	371.5 kN (83,500 lbf)[3]
Specific impulse	300 s (2.9 km/s)
Burn time	105 seconds
Second stage (Enhanced) – M-35
Powered by	1 solid
Maximum thrust	445 kN (100,000 lbf)[3]
Specific impulse	295 s (2.89 km/s)[5]
Burn time	129 seconds [5]
Second stage (Epsilon S) – E-21[2]
Powered by	1 solid
Maximum thrust	610 kN (140,000 lbf)[2]
Specific impulse	294.5 s (2.888 km/s)[2]
Burn time	120 seconds[2]
Third stage (Demonstration Flight) – KM-V2b
Powered by	1 solid
Maximum thrust	99.8 kN (22,400 lbf)[3]
Specific impulse	301 s (2.95 km/s)
Burn time	90 seconds
Third stage (Enhanced) – KM-V2c
Powered by	1 solid
Maximum thrust	99.6 kN (22,400 lbf)[3]
Specific impulse	299 s (2.93 km/s)[5]
Burn time	91 seconds[5]
Third stage (Epsilon S) – E-31[6]
Powered by	1 solid
Maximum thrust	135 kN (30,000 lbf)[6]
Specific impulse	~295 s (2.89 km/s)
Burn time	108 seconds[6]
Fourth stage (Optional) – CLPS
Maximum thrust	40.8 N (9.2 lbf)
Specific impulse	215 s (2.11 km/s)[3]
Burn time	1100 seconds (maximum)
Propellant	Hydrazine

Vehicle description

The development aim is to reduce the US$70 million launch cost of an M-V;^[8] the Epsilon costs US$38 million per launch.^[9] Development expenditures by JAXA exceeded US$200 million.^[9]

To reduce the cost per launch the Epsilon uses the existing SRB-A3, a solid rocket booster on the H-IIA rocket, as its first stage. Existing M-V upper stages will be used for the second and third stages, with an optional fourth stage available for launches to higher orbits. The J-I rocket, which was developed during the 1990s but abandoned after just one launch, used a similar design concept, with an H-II booster and Mu-3S-II upper stages.^[10]

The Epsilon is expected to have a shorter launch preparation time than its predecessors;^[11][12][13] a function called "mobile launch control" greatly shortens the launch preparation time, and needs only eight people at the launch site,^[14] compared with 150 people for earlier systems.^[15]

The rocket has a mass of 91 t (90 long tons; 100 short tons) and is 24.4 m (80 ft) tall and 2.5 m (8 ft 2 in) in diameter.^[16][17]

Enhanced version

After the successful launch of the Epsilon first flight (demonstration flight), the improvement plan was decided to handle the planned payloads (ERG and ASNARO-2).^[18]

Requirements for the improvement:^[18]

• Apogee ≧ 28700 km (summer launch), ≧ 31100 km (winter launch) of a 365 kg payload
• Sun-synchronous orbit (500 km) of a ≧ 590 kg payload
• Larger fairing

Planned characteristics:^[18]

• Height: 26.0 m
• Diameter: 2.5 m
• Mass: 95.1 t (Standard) / 95.4 t (optional 4th stage (post-boost stage))

Catalog performance according to IHI Aerospace:^[19]

• Low Earth orbit 250 km × 500 km for 1.5 t
• Sun-synchronous orbit 500 km × 500 km for 0.6 t

Final characteristics:^[7][20]

• Height: 26.0 m
• Diameter: 2.6 m (max), 2.5 m (fairing)
• Mass: 95.4 t (standard) / 95.7 t (optional)

Epsilon S

Epsilon's first stage has been the modified SRB-A3 which is the solid-rocket booster of H-IIA. As the H-IIA is to be decommissioned and to be replaced by H3, Epsilon is to be replaced by a new version, named Epsilon S.^[21]

Major changes of Epsilon S from Epsilon are:^[21]

• The first stage is based on SRB-3, the strap-on solid-rocket booster of H3.
• The third stage is a new design, whereas Epsilon's third stage was based on the M-V's third stage. New third stage is three-axis stabilized using Post-Boost Stage (PBS), whereas Epsilon's third stage was spin-stabilized. Also the third stage is outside the fairing, whereas Epsilon's fairing covered the third stage.
• The Epsilon S Post-Boost Stage is mandatory, whereas Epsilon's PBS was optional.

Planned performance of Epsilon S is:^[21]

• Sun-synchronous orbit (350 – 700 km): ≧ 600 kg
• Low Earth orbit (500 km): ≧ 1400 kg

The first launch of Epsilon S is planned in 2023.^[21]

On July 14, 2023, the solid-fuelled second stage of Epsilon S failed during a test firing.^[22] The root cause was determined to be the "melting and scattering of a metal part from the ignition device", which damaged the propellant and insulation.^[23] Corrective measures were implemented and the stage was tested again on November 26, 2024; however, the second test also resulted in a failure 49 seconds after ignition.^[24]

Launch statistics

Launch outcomes

1

2013

'14

'15

'16

'17

'18

'19

2020

'21

'22

•   Failure
•   Partial failure
•   Success
•   Planned

Launch history

Epsilon launch vehicles are launched from a pad at the Uchinoura Space Center previously used by Mu launch vehicles. The maiden flight, carrying the SPRINT-A scientific satellite, lifted off at 05:00 UTC (14:00 JST) on 14 September 2013. The launch was conducted at a cost of US$38 million.^[25]

On 27 August 2013, the first planned launch of the launch vehicle had to be aborted 19 seconds before liftoff because of a botched data transmission. A ground-based computer had tried to receive data from the launch vehicle 0.07 seconds before the information was actually transmitted.^[26]

The initial version of Epsilon has a payload capacity to low Earth orbit of up to 500 kilograms,^[27][28] with the operational version expected to be able to place 1,200 kg (2,600 lb) into a 250 by 500 km (160 by 310 mi) orbit, or 700 kg (1,500 lb) to a circular orbit at 500 km (310 mi) with the aid of a hydrazine fueled stage.^[9]

Mockup of Epsilon

Flight No.	Date / time (UTC)	Rocket, Configuration	Launch site	Payload	Payload mass	Orbit	Customer	Launch outcome
1	14 September 2013 05:00:00	Epsilon 4 Stages [29]	Uchinoura Space Center	SPRINT-A (HISAKI)	340 kg	LEO	JAXA	Success
	Demonstration Flight
2	20 December 2016 11:00:00 [30]	Epsilon 3 Stages	Uchinoura Space Center	ERG (ARASE)	350 kg [31]	Geocentric	JAXA	Success
3	17 January 2018 21:06:11 [32]	Epsilon 4 Stages [33]	Uchinoura Space Center	ASNARO-2	570 kg	SSO	Japan Space Systems	Success
4	18 January 2019 00:50:20 [34]	Epsilon 4 Stages	Uchinoura Space Center	RAPIS-1 MicroDragon RISESAT ALE-1 OrigamiSat-1 AOBA-VELOX-IV NEXUS	200 kg	SSO	JAXA	Success[30]
	Innovative Satellite Technology Demonstration-1; component demonstration and technology validation.[35]
5	9 November 2021 00:55:16 [36][37]	Epsilon PBS	Uchinoura Space Center	RAISE-2 HIBARI Z-Sat DRUMS TeikyoSat-4 ASTERISC ARICA NanoDragon KOSEN-1	110 kg	SSO	JAXA	Success
	Innovative Satellite Technology Demonstration-2.
6	12 October 2022 00:50:00 [38]	Epsilon 4 Stages	Uchinoura Space Center	RAISE-3 QPS-SAR 3 QPS-SAR 4 MAGNARO MITSUBA KOSEN-2 WASEDA-SAT-ZERO FSI-SAT	110 kg	SSO	JAXA, iQPS	Failure
	RAISE-3 and the six CubeSats were part of Innovative Satellite Technology Demonstration-3. QPS-SAR 3/4 were Epsilon's first commercial satellites launch contracts. Vehicle was destroyed by flight termination system shortly after second stage cutoff due to an attitude control fault.[38][39] A report regarding the cause has been published and is available for viewing, although it is in Japanese.[40]

Planned launches

Date / time (UTC)	Rocket, Configuration	Launch site	Payload	Orbit	Customer
2024[41]	Epsilon S	Uchinoura Space Center	LOTUSat-1[42]	SSO	VNSC
2025	Epsilon S	Uchinoura Space Center	Innovative Satellite Technology Demonstration-4	LEO	JAXA
2027	Epsilon S	Uchinoura Space Center	Innovative Satellite Technology Demonstration-5	LEO	JAXA
July 2028[43]	Epsilon S	Uchinoura Space Center	Solar-C EUVST[44][45]	SSO	JAXA
2028	Epsilon S	Uchinoura Space Center	JASMINE[46]	SSO	JAXA
2029	Epsilon S	Uchinoura Space Center	Innovative Satellite Technology Demonstration-6	LEO	JAXA
2030[47]	Epsilon S	Uchinoura Space Center	HiZ-GUNDAM [ja]	SSO	JAXA
2031	Epsilon S	Uchinoura Space Center	Innovative Satellite Technology Demonstration-7	LEO	JAXA

Sources: Japanese Cabinet^[48]

Internet data leak

In November 2012, JAXA reported that there had been a possible leak of rocket data due to a computer virus. JAXA had previously been a victim of cyber-attacks, possibly for espionage purposes.^[49] Solid-fuel rocket data potentially has military value,^[49] and Epsilon is considered as potentially adaptable to an intercontinental ballistic missile.^[50] The Japan Aerospace Exploration Agency removed the infected computer from its network, and said its M-V rocket and H-IIA and H-IIB rockets may have been compromised.^[51]

See also

• Spaceflight portal

• Comparison of orbital launchers families
• Comparison of orbital launch systems