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Image Credit: NASA/Terry Zaperach.

Antares to launch Cygnus freighter to the ISS

A Northrop Grumman Antares 230+ rocket is scheduled to launch the company’s Cygnus CRS-16 resupply freighter into low Earth orbit and toward the International Space Station (ISS) on Tuesday evening. The two-stage rocket is scheduled to blast off from Pad 0A at the Mid-Atlantic Regional Spaceport (MARS) on Wallops Island in the US state of Virginia, on August 10 at 17:56 EDT (local time) / 21:56 UTC.

After about two days in orbit, the resupply vehicle is expected to rendezvous with the ISS on August 12, where it will be caught by the two astronauts Megan McArthur and Thomas Pesquet, using the station’s Canadarm2 robotic arm. The Cygnus will then be berthed to the Unity module’s Earth-facing docking port by flight controllers on the ground.

The spacecraft, named “S.S. Ellison Onizuka” after the first Asian American astronaut, will remain attached to the International Space Station for about three months, before departing the orbital laboratory. The freighter will re-enter Earth’s atmosphere over the Pacific Ocean soon after, burning up in the atmosphere during this process.

The mission will be the fifth launch of the Antares 230+ rocket, Northrop Grumman’s in total 16th resupply mission for NASA and the fifth under the agency’s Commercial Resupply Services-2 contract .

The Cygnus space freighter

The Cygnus is an uncrewed freighter, supplying the International Space Station since 2013 on a regular basis.

The vehicle consists of the Northrop Grumman developed service module with the solar arrays, communications, guidance and navigation systems and the Thales Alenia Space built pressurized cargo module.

The Enhanced Cygnus, the configuration currently in active service, is 4.86 m in length, 3.07 m in diameter and has a dry mass of about 1800 kg. The vehicle provides a volume of 27 m³ and is capable of delivering over 3,000 kg of freight to the ISS.

The resupply freighter has so far completed 14th succeessful missions to the ISS. All except of three crafts have been launched on Northrop Grumman’s Antares rockets, the other three on the Atlas V 401 rockets of the United Launch Alliance. That was done to continue cargo deliveries to the ISS, after a launch failure of an Antares rocket in 2014 grounded the rocket.

An Enhanced Cygnus attached to the ISS’ Canadarm2 robotic arm. Image Credit: NASA.

The Antares launch vehicle

The Antares is a two-stage, medium-lift launch vehicle operated by Northrop Grumman and in service since 2013. The Antares 230+, the configuration currently in service, is able to carry up to 8,000 kg into a low Earth orbit and its used to launch Northrop Grumman’s Cygnus space freighters into space and on their journey to the International Space Station.

The Antares 230+’s first stage is 27.6 m in length, 3.90 m in diameter and is powered by two Russian RD-181 rocket engines, burning liquid oxygen (LOX) and the rocket kerosene RP-1 as propellants. The stage has a burn time of about 3 1/2 minutes, before it separates from the second stage and crashs into the Atlantic Ocean.

As an upper stage, the Antares 230+ is equipped with a Castor 30XL solid rocket motor, which ignites about 50 s after stage separation. The stage is 2.3 m in diamter and has a launch mass of over 26 tonnes.

The launcher’s payload fairing is 8.3 m in height, has an outer diameter of 3.9 m and provides a volume of 57.5 m³

The rocket can in theory be launched with an additional Orbit Adjust Module (OAM), STAR 48BV or Orion 38 third stage, depending on the mission’s requirements. So far no Antares has ever been launched with a third stage.

If all goes according to plan, Tuesday’s flight will be the 15th launch of an Antares, the fifth of the Antares 230+ configuration and the 14th successful mission conducted by the rocket.

An Antares blasts off from Pad 0A at the Mid-Atlantic Regional Spaceport. Image Credit: NASA/Bill Ingalls.

Mission profile

At T 0, the two Russian liquid oxygen / RP-1 fueled RD-181 rocket engines will ignite, lifting the rocket off Pad 0A and toward low Earth orbit.

After about 208 seconds of flight, propellant levels in Antares’ first stage deplete and the engines shut down ahead of stage separation followed just moments later.

At around T+250 s and at an altitude of 140 kilometers, the two payload fairing halves will be jettisoned from the launch vehicle, exposing the Cygnus freighter to the vacuum of space.

Almost 50 seconds after stage separation, the solid-fueled Castor 30XL second stage will ignite, boosting the freighter into its preliminary transfer orbit. Burn out of the solid rocket motor and orbit insertion are expected to occur 411 s after liftoff at an altitude of ~180 km.

The S.S. Ellison Onizuka will be separated from the Castor 30XL upper stage about 120 second later at T+9 min 5 s, completing Antares’ mission.

Once in orbit, the Cygnus will deploy its two solar arrays and will utilze its own onboard propulsion system to raise its orbit ahead of the arrival at the International Space Station.

Cargo onboard Cygnus

The S.S. Ellison Onizuka resupply vehicle will carry a total of 3,723 kg of research equipment, crew supplies and hardware to the orbital laboratory. The cargo is composed of 3,676 kg of pressurized and 48 kg of unpressurized cargo.

The 3,723 kg can be divided into 1,396 kg of crew supplies,1,064 kg of science investigations, 1,037 kg of vehicle hardware, 44 kg of computer resources and 15 kg of spacewalk equipment.

Once all cargo is unloaded from the Cygnus, the station’s crew will begin loading trash into the unpiloted spacecraft. It will later burn up in Earth’s atmosphere together with the freighter itself.


Sources:

https://www.nasa.gov/content/overview-for-northrop-grummans-16th-commercial-resupply-mission

https://www.northropgrumman.com/space/cygnus-spacecraft/

https://earth.esa.int/web/eoportal/satellite-missions/i/iss-cygnus

https://www.northropgrumman.com/wp-content/uploads/Antares-User-Guide-1.pdf

https://www.northropgrumman.com/space/antares-rocket/

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