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Eclipse
Photo: Blervis · CC0 (opens commons.wikimedia.org)

Eclipse

by Firefly AerospaceUS

ProtoStage 2 of 5

Main flight parts being built and tested ahead of a first launch.

Updated 29 May 2025Checked 25 Sep0 updates this week

Milestones

Next · First launch
  1. Program announced with Northrop Grumman (as MLV)Aug 2022Complete.
  2. First launchNot yet reached.

Most important updates

  • 29 May 2025

Physics limits

  • The rocket equation makes payload a sliver of launch massOrbit needs about 9.4 km/s of speed change including losses. Fuel needed grows exponentially with that, so even the best rockets put only 2 to 5% of their liftoff mass into low orbit.
  • Chemical propellants have a hard energy ceilingExhaust speed is set by the energy in the chemical bonds. Methane-oxygen tops out near 3.7 km/s and hydrogen-oxygen near 4.5 km/s; no engine design can beat the chemistry.
  • Every kilogram used to come home is a kilogram not carriedA returning booster keeps fuel for boostback and landing, plus legs or fins; this costs roughly 25 to 40% of payload versus throwing it away. Upper stages pay even more, since they are going at orbital speed.

How it works

3 parts
Not Eclipse: Northrop Grumman's earlier Antares first stage test-firing its kerosene engines on the pad; Eclipse's first stage replaces it
Not Eclipse: Northrop Grumman's earlier Antares first stage test-firing its kerosene engines on the pad; Eclipse's first stage replaces itPhoto: NASA · Public domain (opens commons.wikimedia.org)
Stages

Two kerosene stages

Both stages burn kerosene and liquid oxygen. The first stage uses Firefly's Miranda engines, also used on Northrop Grumman's Antares 330.

Size

Medium lift

It is sized for about 16 tonnes to low orbit, between small rockets like Alpha and heavy lifters.

Team

Built with Northrop Grumman

Firefly builds it; Northrop Grumman invested, and its Antares 330 uses a first stage from the same design.

Update log

1 update

Thu 29 May 2025

  • Minor: PressFunding

About Firefly Aerospace

The team behind Eclipse

Firefly Aerospace

Blue Ghost Moon lander, Alpha rocket

Firefly builds the Alpha small rocket, the Blue Ghost Moon lander and, with Northrop Grumman, the Eclipse rocket. Blue Ghost made the first fully successful private Moon landing in March 2025. Listed on Nasdaq in Aug 2025.

  • Blue Ghost landed upright on 2 March 2025 and ran NASA experiments for a full lunar day.
  • Alpha failed in flight (Apr 2025) and exploded in a ground test (Sep 2025) before flying again in March 2026.
  • Blue Ghost Mission 2 to the lunar far side is targeted for late 2026.

fireflyspace.com (opens fireflyspace.com)Company profile →

Founded
20179 yrs
Headquarters
United States
Status
Public
Listed
FLY (opens google.com)NASDAQ
Valuation
public
Last round
IPO (Nasdaq) · $868M7 Aug 2025
Works in
SpaceflightMoon & deep space
Coverage
3 programs · 15 updateslatest 9 Sep 2026checked 25 Sep
Customers
NASA (opens nasa.gov)
Partners
Northrop Grumman (opens northropgrumman.com)
Investors
AE Industrial Partners (opens aeroequity.com)
People
Jason Kim (opens fireflyspace.com)CEO
Primer