# Falcon 9 Block 4

> fourth major version of the Falcon 9 rocket

**Wikidata**: [Q58924629](https://www.wikidata.org/wiki/Q58924629)  
**Source**: https://4ort.xyz/entity/falcon-9-block-4

## Summary
The Falcon 9 Block 4 is the fourth major version of SpaceX's Falcon 9 orbital launch vehicle, designed for partial reusability. It operated from 2017 to 2018, serving as a transitional model between earlier variants and the upgraded Block 5. This rocket supported critical satellite deployments and scientific missions, contributing to SpaceX's advancements in reusable rocket technology.

## Key Facts
- **First Flight**: August 14, 2017, at 16:31 UTC (Flight 39).
- **Retirement Date**: June 29, 2018, at 09:42 UTC.
- **Manufacturer**: SpaceX (United States).
- **Replaced**: Falcon 9 Full Thrust.
- **Replaced By**: Falcon 9 Block 5.
- **Key Components**: 9 Merlin 1D engines, 1 Merlin 1D Vacuum engine, and a reusable first-stage booster.
- **Notable Payloads**: Iridium satellites, GRACE-FO 1 and 2 science satellites.
- **Associated Boosters**: B1039, B1040, B1041, B1042, B1043, B1044, B1045 (all expended).

## FAQs
### Q: When did the Falcon 9 Block 4 first launch?
A: The Falcon 9 Block 4 debuted on August 14, 2017, during its first mission (Flight 39).

### Q: Why was the Falcon 9 Block 4 retired?
A: It was retired in June 2018 in favor of the upgraded Falcon 9 Block 5, which offered improved reusability and performance.

### Q: What notable missions did the Falcon 9 Block 4 support?
A: It launched Iridium communication satellites and the GRACE-FO science satellites for NASA and Germany.

## Why It Matters
The Falcon 9 Block 4 played a pivotal role in SpaceX's evolution toward fully reusable rockets, refining technologies that reduced launch costs and increased efficiency. By supporting deployments of the Iridium satellite constellation and the GRACE-FO climate research mission, it demonstrated reliability for both commercial and scientific payloads. As a bridge between earlier Falcon 9 variants and the long-term Block 5 design, it facilitated iterative advancements in spaceflight technology, solidifying SpaceX's leadership in the launch services market.

## Notable For
- **Transitional Design**: Served as a critical stepping stone to the Block 5, incorporating incremental upgrades.
- **Iridium Constellation Deployment**: Launched numerous Iridium NEXT satellites to support global communication networks.
- **Scientific Contributions**: Deployed the GRACE-FO satellites, which monitored Earth's gravity field to study climate change.

## Body
### Development and Design
The Falcon 9 Block 4 was part of SpaceX's iterative rocket development strategy, emphasizing reusability. It featured:
- **Engines**: 9 sea-level Merlin 1D engines and 1 vacuum-optimized Merlin 1D Vacuum engine.
- **First-Stage Booster**: Designed for recovery and reuse, though all Block 4 boosters were eventually expended.
- **Fuel System**: Upgraded from previous versions for improved performance.

### Operational History
- **First Flight**: August 14, 2017 (launching 10 Iridium satellites).
- **Final Flight**: June 29, 2018 (deploying GRACE-FO 1 and 2).
- **Notable Missions**:
  - **Iridium-4 through Iridium-8**: Deployed 50 Iridium NEXT satellites across five launches.
  - **GRACE-FO**: Launched twin satellites to track water movement and ice melt.

### Legacy
Though retired after 12 months, the Block 4 validated reusability concepts and informed the design of the Block 5, which became SpaceX's workhorse rocket. Its missions supported telecommunications, Earth science, and SpaceX's broader goal of making space access routine and affordable.

## Schema Markup
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  "@type": "Rocket",
  "name": "Falcon 9 Block 4",
  "description": "Fourth major version of the Falcon 9 rocket",
  "manufacturer": "SpaceX",
  "countryOfOrigin": "United States",
  "dateProduced": "2017",
  "dateRetired": "2018-06-29",
  "sameAs": ["https://www.wikidata.org/wiki/Q111111111"],
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