# Delta IV Heavy

> retired expendable launch system in the Delta rocket family

**Wikidata**: [Q249492](https://www.wikidata.org/wiki/Q249492)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Delta_IV_Heavy)  
**Source**: https://4ort.xyz/entity/delta-iv-heavy

## Summary
The Delta IV Heavy is a retired heavy-lift launch vehicle and part of the Delta rocket family, designed to carry large payloads into space. It was operated by United Launch Alliance and served as one of the most powerful rockets in the U.S. fleet before its retirement in 2024.

## Key Facts
- **Retirement Date**: Officially retired on April 9, 2024, after its final launch.
- **Manufacturer**: Built by United Launch Alliance (ULA).
- **Payload Capacity**: Could lift 28,370 kg to low Earth orbit (LEO) and 13,810 kg to geostationary transfer orbit (GTO).
- **Dimensions**: 70.7 meters tall and 15 meters wide.
- **First Flight**: Launched for the first time on December 21, 2004.
- **Launch Sites**: Operated from Cape Canaveral Space Launch Complex 37B and Vandenberg Space Launch Complex 6.
- **Configuration**: Consisted of three Common Booster Cores and one Delta Cryogenic Second Stage.
- **Mass**: Launch weight of 733,400 kg.
- **Notable Payloads**: Launched missions like the Parker Solar Probe and various reconnaissance satellites (e.g., KH-11 series, Orion satellites).

## FAQs
### Q: What was the Delta IV Heavy used for?
A: The Delta IV Heavy was primarily used to launch heavy payloads, including military reconnaissance satellites, scientific probes (like the Parker Solar Probe), and other high-priority missions for the U.S. government and NASA.

### Q: When did the Delta IV Heavy retire?
A: The Delta IV Heavy was retired on April 9, 2024, after its final mission, marking the end of the Delta rocket family’s operational history.

### Q: How powerful was the Delta IV Heavy?
A: It was one of the most powerful rockets in the U.S. fleet, capable of lifting up to 28,370 kg to low Earth orbit and 13,810 kg to geostationary transfer orbit.

### Q: Who operated the Delta IV Heavy?
A: The rocket was manufactured and operated by United Launch Alliance (ULA), a joint venture between Boeing and Lockheed Martin.

### Q: What replaced the Delta IV Heavy?
A: While the source material does not specify a direct replacement, newer heavy-lift rockets like ULA’s Vulcan Centaur and SpaceX’s Falcon Heavy are expected to fill its role.

## Why It Matters
The Delta IV Heavy played a critical role in U.S. space exploration and national security, enabling the launch of high-priority payloads that smaller rockets could not handle. Its heavy-lift capability was essential for deploying advanced reconnaissance satellites, deep-space probes like the Parker Solar Probe, and other mission-critical assets. As a flagship vehicle of the Delta rocket family, it represented decades of engineering expertise and reliability. Its retirement marks the end of an era in American rocketry, transitioning to more modern and cost-effective launch systems. The Delta IV Heavy’s legacy includes supporting both scientific discovery and defense operations, cementing its importance in the history of spaceflight.

## Notable For
- **Heavy-Lift Capability**: One of the most powerful operational rockets in the U.S. at the time of its service, with a LEO payload capacity of 28,370 kg.
- **Military and Scientific Missions**: Launched classified reconnaissance satellites (e.g., KH-11 series, Orion satellites) and NASA’s Parker Solar Probe.
- **Unique Configuration**: Featured three Common Booster Cores strapped together, a design that maximized thrust.
- **Final Delta Rocket**: Its retirement in 2024 marked the end of the Delta rocket family, which had been in service since the 1960s.
- **High Reliability**: Known for its consistency in delivering critical payloads to orbit, earning trust from U.S. government agencies.

## Body
### Overview
The Delta IV Heavy was an expendable heavy-lift launch vehicle developed as part of the Delta IV family, itself a successor to the long-running Delta rocket program. It was designed to meet the demands of launching large, complex payloads for both civilian and military applications.

### Technical Specifications
- **Height**: 70.7 meters (232 feet).
- **Width**: 15 meters (49 feet).
- **Mass at Lift-off**: 733,400 kg (1,617,000 lbs).
- **Payload Capacity**:
  - 28,370 kg to low Earth orbit (LEO).
  - 13,810 kg to geostationary transfer orbit (GTO).
- **Stages**:
  - **First Stage**: Three Common Booster Cores (CBCs), each powered by an RS-68 engine.
  - **Second Stage**: Delta Cryogenic Second Stage (DCSS), powered by an RL10B-2 engine.

### Development and Operational History
- **First Launch**: December 21, 2004, from Cape Canaveral Space Launch Complex 37B.
- **Launch Sites**:
  - Cape Canaveral Space Launch Complex 37B (Florida).
  - Vandenberg Space Launch Complex 6 (California).
- **Manufacturer**: United Launch Alliance (ULA), formed in 2006 as a joint venture between Boeing and Lockheed Martin.
- **Retirement**: The final Delta IV Heavy launch occurred on April 9, 2024, concluding the Delta rocket family’s operational history.

### Notable Missions
- **Parker Solar Probe (2018)**: A NASA mission to study the Sun’s outer corona, launched aboard a Delta IV Heavy.
- **Reconnaissance Satellites**: Launched multiple classified payloads for the U.S. National Reconnaissance Office (NRO), including the KH-11 series and Orion satellites.
- **Other Payloads**: Supported missions like the Jupiter Icy Moons Orbiter (proposed) and Innovative Interstellar Explorer (proposed).

### Legacy
The Delta IV Heavy was a cornerstone of U.S. heavy-lift capability for nearly two decades. Its retirement reflects the transition toward more cost-effective and reusable launch systems, such as ULA’s Vulcan Centaur and SpaceX’s Falcon Heavy. Despite its high operational costs, the Delta IV Heavy remained a reliable workhorse for critical national security and scientific missions.

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## References

1. [The Next-Generation Heavy-Lift Vehicle—The Inaugural Flight of the EELV Delta IV Heavy](https://www.ulalaunch.com/docs/default-source/evolution/the-next-generation-heavy-lift-vehicle-the-inaugural-flight-of-the-eelv-delta-iv-heavy.pdf)
2. Freebase Data Dumps. 2013
3. [After a fiery finale, the Delta rocket family now belongs to history. Ars Technica. 2024](https://arstechnica.com/space/2024/04/after-a-fiery-finale-the-delta-rocket-family-now-belongs-to-history/)
4. [Source](https://www.ulalaunch.com/docs/default-source/rockets/delta-iv-heavy-cutaway.pdf)
5. [Source](http://www.astronautix.com/d/delta4h.html)