Epsilon (rocket)

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title: "Epsilon (rocket)" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["2013-in-spaceflight", "solid-fuel-rockets", "space-launch-vehicles-of-japan", "vehicles-introduced-in-2013", "expendable-space-launch-systems"] description: "JAXA small-lift rocket family" topic_path: "geography/japan" source: "https://en.wikipedia.org/wiki/Epsilon_(rocket)" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary JAXA small-lift rocket family ::

::data[format=table title="Infobox rocket"]

Field	Value
name	Epsilon
image	Epsilon rocket F2.jpg
caption	Epsilon flight F2 before launch in December 2016
function	Launch vehicle
country-origin	Japan
cpl	US$39 million
height	24.4 m (Demonstration Flight)
26 m (Enhanced)
27.2 m (Epsilon S)
diameter	2.5 m
mass	91 t (Demonstration Flight)
95.4 t (Enhanced)
~100 t (Epsilon S)
stages	3–4
capacities	{{Infobox rocket/payload
location	250 x 500 km orbit
Standard 3 stages configuration
kilos	1500 kg
location	500 km orbit
Optional 4 stages configuration
kilos	700 kg
location	500 km orbit
Epsilon S
kilos	1400 kg
location	500 km SSO
Optional 4 stages configuration
kilos	590 kg
location	700 km SSO
Epsilon S
kilos	600 kg
status	Active
sites	Uchinoura
launches	6
success	5
fail	1
partial	0
first	14 September 2013
last	12 October 2022
stagedata	{{Infobox rocket/stage
type	stage
stageno	First
diff	Demonstration Flight/Enhanced
name	SRB-A3
engines	1 solid
thrust	2271 kN
SI	284 isp
burntime	116 seconds
type	stage
stageno	First
diff	Epsilon S
name	SRB-3
engines	1 solid
thrust	2158 kN
SI	283.6 isp
burntime	105 seconds
type	stage
stageno	Second
diff	Demonstration Flight
name	M-34c
engines	1 solid
thrust	371.5 kN
SI	300 isp
burntime	105 seconds
type	stage
stageno	Second
diff	Enhanced
name	M-35
engines	1 solid
thrust	445 kN
SI	295 isp
burntime	129 seconds
type	stage
stageno	Second
diff	Epsilon S
name	E-21
engines	1 solid
thrust	610 kN
SI	294.5 isp
burntime	120 seconds
type	stage
stageno	Third
diff	Demonstration Flight
name	KM-V2b
engines	1 solid
thrust	99.8 kN
SI	301 isp
burntime	90 seconds
type	stage
stageno	Third
diff	Enhanced
name	KM-V2c
engines	1 solid
thrust	99.6 kN
SI	299 isp
burntime	91 seconds
type	stage
stageno	Third
diff	Epsilon S
name	E-31
engines	1 solid
thrust	135 kN
SI	~295 isp
burntime	108 seconds
type	stage
stageno	Fourth
diff	Optional
name	CLPS
thrust	40.8 N
SI	215 isp
burntime	1100 seconds (maximum)
fuel	Hydrazine
::

| name = Epsilon | image = Epsilon rocket F2.jpg | caption = Epsilon flight F2 before launch in December 2016

| function = Launch vehicle | manufacturer = | country-origin = Japan | cpl = US$39 million | height = 24.4 m (Demonstration Flight) 26 m (Enhanced) 27.2 m (Epsilon S) | diameter = 2.5 m | mass = 91 t (Demonstration Flight) 95.4 t (Enhanced) ~100 t (Epsilon S) | stages = 3–4

| capacities = {{Infobox rocket/payload | location = 250 x 500 km orbit Standard 3 stages configuration | kilos = 1500 kg | location = 500 km orbit Optional 4 stages configuration | kilos = 700 kg | location = 500 km orbit Epsilon S | kilos = 1400 kg | location = 500 km SSO Optional 4 stages configuration | kilos = 590 kg | location = 700 km SSO Epsilon S | kilos = 600 kg

| status = Active | sites = Uchinoura | launches = 6 | success = 5 | fail = 1 | partial = 0 | first = 14 September 2013 | last = 12 October 2022

| stagedata = {{Infobox rocket/stage | type = stage | stageno = First | diff = Demonstration Flight/Enhanced | name = SRB-A3 | engines = 1 solid | thrust = 2271 kN | SI = 284 isp | burntime = 116 seconds | fuel = | type = stage | stageno = First | diff = Epsilon S | name = SRB-3 | engines = 1 solid | thrust = 2158 kN | SI = 283.6 isp | burntime = 105 seconds | fuel = | type = stage | stageno = Second | diff = Demonstration Flight | name = M-34c | engines = 1 solid | thrust = 371.5 kN | SI = 300 isp | burntime = 105 seconds | fuel = | type = stage | stageno = Second | diff = Enhanced | name = M-35 | engines = 1 solid | thrust = 445 kN | SI = 295 isp | burntime = 129 seconds | fuel = | type = stage | stageno = Second | diff = Epsilon S | name = E-21 | engines = 1 solid | thrust = 610 kN | SI = 294.5 isp | burntime = 120 seconds | fuel = | type = stage | stageno = Third | diff = Demonstration Flight | name = KM-V2b | engines = 1 solid | thrust = 99.8 kN | SI = 301 isp | burntime = 90 seconds | fuel = | type = stage | stageno = Third | diff = Enhanced | name = KM-V2c | engines = 1 solid | thrust = 99.6 kN | SI = 299 isp | burntime = 91 seconds | fuel = | type = stage | stageno = Third | diff = Epsilon S | name = E-31 | engines = 1 solid | thrust = 135 kN | SI = ~295 isp | burntime = 108 seconds | fuel = | type = stage | stageno = Fourth | diff = Optional | name = CLPS | engines = | thrust = 40.8 N | SI = 215 isp | burntime = 1100 seconds (maximum) | fuel = Hydrazine

The Epsilon Launch Vehicle, or Epsilon rocket (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.

Vehicle description

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

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.

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

The rocket has a mass of 91 t and is 24.4 m tall and 2.5 m in diameter.

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).

Requirements for the improvement:

• 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:

• 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:

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

Final characteristics:

• 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.

Major changes of Epsilon S from Epsilon are:

• 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:

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

The first launch of Epsilon S was originally planned for 2023. However, on July 14, 2023, the solid-fueled second stage of Epsilon S failed during a test firing. 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. 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, derailing plans for a launch by 31 March 2025.

In July 2025, NHK reported that JAXA was reviewing its development plans for the Epsilon S. In order to expedite the first launch, it was proposed to defer planned improvements to the second stage and revert to using the proven, existing design of Epsilon. While this would entail performance being lower than originally planned, it could enable a launch around the end of 2026 at the soonest.

Due to delays with the development of Epsilon S, the RAISE-4 spacecraft and 8 small satellites originally planned for launch on Epsilon S was moved to launch over 2 launches by Rocket Lab's Electron rocket in December 2025 and Q1 2026 respectively.

Launch statistics

Launch outcomes

| float = center | width = 420 | height = 320 | stack = 1 | group 1 = 0:0:0:0:0:0:0:0:0:1 | group 2 = 0:0:0:0:0:0:0:0:0:0 | group 3 = 1:0:0:1:0:1:1:0:1:0 | group 4 = 0:0:0:0:0:0:0:0:0:0 | colors = FireBrick: Orange: ForestGreen: LightBlue | group names = Failure: Partial failure: Success: Planned | x legends = 2013: '14: '15: '16: '17: '18: '19: 2020: '21: '22 | y tick marks = 1

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.

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.

The initial version of Epsilon has a payload capacity to low Earth orbit of up to 500 kilograms, with the operational version expected to be able to place 1200 kg into a 250 by orbit, or 700 kg to a circular orbit at 500 km with the aid of a hydrazine fueled stage. ::figure[src="https://upload.wikimedia.org/wikipedia/commons/1/17/Epsilon_Launch_Vehicle_Model.jpg" caption="Mockup of Epsilon"] ::

::data[format=table] | Flight No. | Date / time (UTC) | Rocket, Configuration | Launch site | Payload | Payload mass | Orbit | Customer | Launch outcome | 1 | 2 | 3 | 4 | 5 | 6 | |---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| | 14 September 2013 05:00:00 | url=http://www.jaxa.jp/press/2013/09/20130914_epsilon_e.html|title=Launch Result of Epsilon-1 with SPRINT-A aboard|publisher=JAXA|date=14 September 2013|access-date=18 September 2013|archive-date=7 April 2014|archive-url=https://web.archive.org/web/20140407064419/http://www.jaxa.jp/press/2013/09/20130914_epsilon_e.html}} | Uchinoura Space Center | SPRINT-A (HISAKI) | 340 kg | LEO | JAXA | | | | | | | | | | Demonstration Flight | | | | | | | | | | | | | | | | url=http://global.jaxa.jp/press/2016/12/20161220_epsilon2.html|title=Success of Epsilon-2 Launch with ERG Aboard|publisher=JAXA|date=December 20, 2016|access-date=December 20, 2016}} | Epsilon 3 Stages | Uchinoura Space Center | ERG (ARASE) | 350 kg | Geocentric | JAXA | | | | | | | | | | | | | | | | | | | | | | | | | | title=JAXA launches Epsilon-3 rocket|url=https://www3.nhk.or.jp/nhkworld/en/news/20180118_08/|access-date=17 January 2018|agency=NHK World |issue=17 January 2018|archive-url=https://web.archive.org/web/20180118064647/https://www3.nhk.or.jp/nhkworld/en/news/20180118_08/|archive-date=January 18, 2018}} | url=http://spaceflight101.com/asnaro-2/epsilon-3-launches-asnaro-2/|title=Pre-Dawn Epsilon Liftoff Sends Japanese Radar-Imaging Satellite into Orbit|publisher=Spaceflight101|access-date=17 January 2018|archive-date=18 January 2018|archive-url=https://web.archive.org/web/20180118064701/http://spaceflight101.com/asnaro-2/epsilon-3-launches-asnaro-2/|url-status=dead}} | Uchinoura Space Center | ASNARO-2 | 570 kg | SSO | Japan Space Systems | | | | | | | | | | | | | | | | | | | | | | | | | | 18 January 2019 00:50:20 | Epsilon 4 Stages | Uchinoura Space Center | RAPIS-1 MicroDragon RISESAT ALE-1 OrigamiSat-1 AOBA-VELOX-IV NEXUS | 200 kg | SSO | JAXA | | | | | | | | | | Innovative Satellite Technology Demonstration-1; component demonstration and technology validation. | | | | | | | | | | | | | | | | 9 November 2021 00:55:16 | Epsilon PBS | Uchinoura Space Center | RAISE-2 HIBARI Z-Sat DRUMS TeikyoSat-4 ASTERISC ARICA NanoDragon KOSEN-1 | 110 kg | SSO | JAXA | | | | | | | | | | Innovative Satellite Technology Demonstration-2. | | | | | | | | | | | | | | | | url=https://www.nasaspaceflight.com/2022/10/epsilon-raise-3/|title=Epsilon launched by JAXA|date=12 October 2022|access-date=12 October 2022}} | 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 | | | | | | | | | | 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. A report regarding the cause has been published and is available for viewing, although it is in Japanese. | | | | | | | | | | | | | | | ::

Planned launches

::data[format=table] | Date / time (UTC) | Rocket, Configuration | Launch site | Payload | Orbit | Customer | |---|---|---|---|---|---| | 2026 | Epsilon S | Uchinoura Space Center | LOTUSat-1 | SSO | VNSC | | 2027 | Epsilon S | Uchinoura Space Center | Innovative Satellite Technology Demonstration-5 | LEO | JAXA | | July 2028 | Epsilon S | Uchinoura Space Center | Solar-C EUVST | SSO | JAXA | | 2028 | Epsilon S | Uchinoura Space Center | JASMINE | SSO | JAXA | | 2029 | Epsilon S | Uchinoura Space Center | Innovative Satellite Technology Demonstration-6 | LEO | JAXA | | 2030 | Epsilon S | Uchinoura Space Center | | SSO | JAXA | | 2031 | Epsilon S | Uchinoura Space Center | Innovative Satellite Technology Demonstration-7 | LEO | JAXA | ::

Sources: Japanese Cabinet

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. Solid-fuel rocket data potentially has military value, 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.{{cite news|url=http://www.3news.co.nz/Japans-space-agency-probes-possible-data-leak/tabid/1160/articleID/278923/Default.aspx |publisher=3 News NZ|title=Virus hits Japan space programme|date=December 3, 2012|access-date= December 2, 2012|archive-url=https://web.archive.org/web/20130922235440/http://www.3news.co.nz/Japans-space-agency-probes-possible-data-leak/tabid/1160/articleID/278923/Default.aspx|archive-date=September 22, 2013}}

References

References

1. (16 August 2017). "U.S. GAO - Surplus Missile Motors: Sale Price Drives Potential Effects on DOD and Commercial Launch Providers". U.S. Government Accountability Office.
2. (7 July 2023). "イプシロンSロケット開発状況に関する説明会". [[JAXA]].
3. "イプシロンロケットの開発および準備状況". JAXA.
4. "H3 Launch Vehicle Brochure".
5. (2019). "Development and Flight Results of Solid Propulsion System for Enhanced Epsilon Launch Vehicle". Trans. JSASS Aerospace Tech. Japan.
6. (9 June 2023). "イプシロンSロケット第3段モータ（E-31）地上燃焼試験結果".
7. "Epsilon Launch Vehicle". JAXA.
8. (August 11, 2010). "Asteroid probe, rocket get nod from Japanese panel". Spaceflight Now.
9. Clark, Stephen. (September 14, 2013). "Japan's 'affordable' Epsilon rocket triumphs on first flight". Spaceflight Now.
10. (2007). "J-I Launch Vehicle". Japan Aerospace Exploration Agency.
11. "Epsilon launch vehicle". JAXA.
12. (July 10, 2009). "Advanced Solid Rocket Launcher and its Evolution". 27th International Symposium on Space Technology and Science.
13. (July 10, 2009). "A minimized facility concept of the Advanced Solid Rocket launch operation". 27th International Symposium on Space Technology and Science.
14. (1 March 2020). "Current Status of Research on Space Emergency Launch". Journal of Physics: Conference Series.
15. Keating, Fiona. (14 September 2013). "Japan's Laptop-Controlled Space Rocket Blasts Off (video)". International Business Times.
16. (November 9, 2012). "JAXA readies small rocket to break cost, use barriers". Japan Times.
17. [http://www.spaceflight101.com/epsilon-launch-vehicle-information.html Epsilon Launch Vehicle Information]
18. (October 30, 2014). "強化型イプシロンロケット プロジェクト移行審査の結果について".
19. "EPSILON a solid propellant launch vehicle for new age". IHI Aerospace.
20. link. JAXA. (24 November 2016)
21. "Japanese space agency's Epsilon small rocket engine explodes in test".
22. (2023-12-13). "JAXA Identifies Cause of Explosion during Rocket Engine Test".
23. Yamaguchi, Mari. (November 26, 2024). "The engine of Japan's flagship new small rocket explodes during a test for a second time". [[AP News]].
24. (26 November 2024). "Space agency halts Epsilon rocket test after 'boom,' fireball". [[The Asahi Shimbun]].
25. (27 November 2024). "Japan's Epsilon S Rocket Suffers Another Setback". SpacePolicyOnline.com.
26. (16 July 2025). "「イプシロンS」ロケットの2段目 従来型で早期実現目指す方針". NHK News.
27. (10 October 2025). "Rocket Lab Secures Multiple Launches with Japan Aerospace Exploration Agency (JAXA)". Rocket Lab.
28. "Epsilon rocket all aces this time". Asahi Shimbun.
29. (9 September 2013). "Launch rehearsed for new rocket". Japan Times.
30. "Interview: Yasuhiro Morita, Project Manager, Epsilon Launch Vehicle". JAXA.
31. Stephen Clark. (November 5, 2012). "Japan schedules launch of innovative Epsilon rocket". Spaceflight Now.
32. (14 September 2013). "Launch Result of Epsilon-1 with SPRINT-A aboard". JAXA.
33. (December 20, 2016). "Success of Epsilon-2 Launch with ERG Aboard". JAXA.
34. "Exploration of energization and Radiation in Geospace (ERG)". JAXA.
35. "JAXA launches Epsilon-3 rocket".
36. "Pre-Dawn Epsilon Liftoff Sends Japanese Radar-Imaging Satellite into Orbit". Spaceflight101.
37. (18 January 2019). "Epsilon 4 launched by JAXA".
38. "革新的衛星技術実証1号機に搭載する実証テーマ候補". JAXA.
39. (30 October 2021). "Launch Schedule". Spaceflight Now.
40. (June 2021). "革新的衛星技術実証２号機". JAXA.
41. (12 October 2022). "Epsilon launched by JAXA".
42. Clark, Stephen. (18 October 2022). "Failure of Japan's Epsilon rocket blamed on attitude control system". Spaceflight Now.
43. 宇宙航空研究開発機構, 国立研究開発法人. (2023-05-19). "Report on the investigation into the cause of the launch failure of Epsilon Rocket 6.".
44. (10 September 2025). "イプシロンSロケット 第2段モータ再地上燃焼試験における燃焼異常 原因調査状況". JAXA.
45. link. JAXA. (12 June 2020)
46. Shimizu, Toshifumi. (15 December 2023). "SH54A-03 The SOLAR-C EUVST mission: Coronal physics advanced by novel EUV spectroscopy".
47. (December 29, 2020). "NASA Approves Heliophysics Missions to Explore Sun, Earth's Aurora". NASA.
48. "Instruments {{!}} Next-generation solar-observing satellite Solar-C_EUVST". NAOJ.
49. (March 1, 2021). "JASMINE（赤外線位置天文観測衛星）で拓く天の川中心核と地球型惑星の探査". National Astronomical Observatory of Japan.
50. Yonetoku, Daisuke. (8 September 2021). "ガンマ線バーストを用いた初期宇宙・極限時空探査計画HiZ-GUNDAM". Group of Optical and Infrared Astronomers.
51. (22 December 2023). "宇宙基本計画⼯程表 (令和５年度改訂)". [[Cabinet Office (Japan).
52. Iain Thomson. (November 30, 2012). "Malware slurps rocket data from Japanese space agency". The Register.
53. (23 August 2013). "Japan's New Military Buildup Seen as Response to North Korea, China". National Journal.
54. link. JAXA. (12 June 2020)

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