# Cygnus CRS OA-4

> fifth cargo resupply mission to the International Space Station

**Wikidata**: [Q16820623](https://www.wikidata.org/wiki/Q16820623)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Cygnus_OA-4)  
**Source**: https://4ort.xyz/entity/cygnus-crs-oa-4

## Summary
Cygnus CRS OA-4 was the fifth cargo resupply mission to the International Space Station, launched on December 6, 2015, and operated by Orbital ATK. The spacecraft, named S.S. Deke Slayton II, delivered 3513 kg of supplies to the ISS before deorbiting on February 20, 2016.

## Key Facts
- Cygnus CRS OA-4 was the fifth cargo resupply mission to the International Space Station
- It launched on December 6, 2015, at 21:44:57 UTC from Cape Canaveral Space Launch Complex 41
- The spacecraft had a total takeoff mass of 7492 kg and delivered 3513 kg of payload to the ISS
- It was named after Deke Slayton, one of NASA's original Mercury Seven astronauts
- It used an Atlas V 401 launch vehicle (AV-061) provided by United Launch Alliance
- The mission was part of NASA's Commercial Resupply Services program
- It docked with the Unity module on the nadir (Earth-facing) port of the ISS on December 9, 2015
- It remained in orbit for approximately 76 days before deorbiting on February 20, 2016

## FAQs
### Q: What was the purpose of Cygnus CRS OA-4?
A: Cygnus CRS OA-4 was a cargo resupply mission that delivered 3513 kg of supplies, equipment, and science experiments to the International Space Station as part of NASA's Commercial Resupply Services program.

### Q: How did Cygnus CRS OA-4 compare to previous Cygnus missions?
A: It was the fifth successful cargo resupply mission in the program, following the failed Orb-3 mission. It featured the second use of the "Deke Slayton" name, following a previous Cygnus spacecraft.

### Q: What was the mission duration of Cygnus CRS OA-4?
A: The mission lasted approximately 76 days (6545700 seconds), from its launch on December 6, 2015, to its deorbit on February 20, 2016.

### Q: What was the orbital profile of Cygnus CRS OA-4?
A: The spacecraft operated in low Earth orbit with an apoapsis of 4088 km, periapsis of 3979 km, orbital inclination of 51.64°, and an eccentricity of 0.0008.

## Why It Matters
Cygnus CRS OA-4 represented a critical milestone in NASA's partnership with private industry for space station resupply. Coming after the failed Orb-3 mission, it demonstrated the program's resilience and reliability in maintaining the continuous supply line to the International Space Station. The delivery of essential supplies and research equipment supported ongoing scientific experiments and station operations, contributing to the broader objectives of human space exploration. This mission highlighted the success of the Commercial Resupply Services model in providing cost-effective solutions for sustaining human presence in low Earth orbit.

## Notable For
- It was the fifth successful cargo resupply mission in the Cygnus program
- It carried the name S.S. Deke Slayton II, honoring one of NASA's original Mercury Seven astronauts
- It marked a return-to-flight after the previous Orb-3 mission failure
- It successfully docked with the Unity module on the nadir port of the ISS
- It maintained a typical mission duration of approximately 76 days before planned deorbit

## Body
### Mission Overview
Cygnus CRS OA-4 was the fifth cargo resupply mission to the International Space Station conducted by Orbital ATK under NASA's Commercial Resupply Services contract. The spacecraft was officially named S.S. Deke Slayton II, after one of the Mercury Seven astronauts. It launched on December 6, 2015, at 21:44:57 UTC from Cape Canaveral Space Launch Complex 41.

### Launch and Vehicle
The mission utilized an Atlas V 401 launch vehicle (AV-061) provided by United Launch Alliance. The spacecraft had a total takeoff mass of 7492 kg, including its payload of 3513 kg of supplies and equipment for the ISS. The launch marked the return-to-flight for the program after the previous Orb-3 mission failed during launch.

### Orbital Parameters
- Apoapsis: 4088 km
- Periapsis: 3979 km
- Orbital inclination: 51.64°
- Orbital eccentricity: 0.0008
- Semi-major axis: 67815 km
- Mission duration: 6545700 seconds (approximately 76 days)

### Docking and Operations
The spacecraft successfully docked with the Unity module on the nadir port of the ISS on December 9, 2015. It remained attached to the station until February 19, 2016, when it was unberthed in preparation for its deorbit.

### Mission End
Cygnus CRS OA-4 was deorbited on February 20, 2016, through atmospheric entry as planned, marking the end of its mission.

## Schema Markup
```json
{
  "@context": "https://schema.org",
  "@type": "Thing",
  "name": "Cygnus CRS OA-4",
  "description": "Fifth cargo resupply mission to the International Space Station",
  "url": "https://commons.wikimedia.org/wiki/Special:FilePath/Orbital_Sciences_CRS_Flight_4_Patch.png",
  "sameAs": [
    "https://www.wikidata.org/wiki/Q41101",
    "https://en.wikipedia.org/wiki/Cygnus_OA-4"
  ],
  "additionalType": "uncrewed spaceflight",
  "startDate": "2015-12-06",
  "endDate": "2016-02-20",
  "location": {
    "@type": "Place",
    "name": "International Space Station"
  },
  "performer": {
    "@type": "Organization",
    "name": "Orbital ATK"
  },
  "vehicle": {
    "@type": "Vehicle",
    "name": "Cygnus"
  },
  "payload": {
    "@type": "QuantitativeValue",
    "value": "3513",
    "unitCode": "KGM"
  },
  "mass": {
    "@type": "QuantitativeValue",
    "value": "7492",
    "unitCode": "KGM"
  },
  "orbit": {
    "@type": "Orbit",
    "apogee": {
      "@type": "QuantitativeValue",
      "value": "4088",
      "unitCode": "KMT"
    },
    "perigee": {
      "@type": "QuantitativeValue",
      "value": "3979",
      "unitCode": "KMT"
    },
    "inclination": "51.64",
    "eccentricity": "0.0008"
  }
}

## References

1. Jonathan's Space Report