Cygnus OA-8 (CRS-8 ) - Antares-230 - MARS LP-0A - 12.11.1017 12:19 UTC

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11/11/2017 12:08

Chilldown of the liquid oxygen loading system at launch pad 0A is now underway.

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https://spaceflightnow.com/2017/11/11/antares-rockets-launch-timeline-on-the-oa-8-cargo-mission/

Antares rocket's launch timeline on the OA-8 cargo mission
November 11, 2017 Stephen Clark


Credit: Orbital ATK

Orbital ATK's Antares rocket will deliver the commercial Cygnus supply ship to an orbit with an altitude between 117 miles (189 kilometers) and 184 miles (296 kilometers) within about nine minutes of liftoff Saturday from Virginia's Eastern Shore.

Спойлер

The rocket's two RD-181 engines will ignite around 3.6 seconds before liftoff from pad 0A at the Mid-Atlantic Regional Spaceport, a complex owned by the state of Virginia at NASA's Wallops Flight Facility.

Launch is timed for 7:37 a.m. EST (1237 GMT) Saturday.

The first stage's two RD-181 engines will power up to 864,000 pounds of thrust and burn for 3 minutes, 35 seconds to accelerate the rocket to more than 8,750 mph (3.9 kilometers per second) and an altitude of 61 miles (99 kilometers), then separate from the upper stage's Castor 30XL motor about six seconds later.

The launch, known as OA-8 in Orbital ATK's station resupply manifest, will be the second Antares mission using RD-181 engines, which the company ordered from the Russian engine-builder NPO Energomash to replace decades-old Russian-built AJ26 engines blamed for an Antares rocket crash seconds after liftoff in October 2014.

The RD-181 engines performed better than predicted on an Antares launch in October 2016, giving engineers confidence to loosen performance limits for the OA-8 launch. The engines produce more thrust than the AJ26s, and they will be programmed to fire around six seconds longer on the OA-8 launch than on the last Antares flight.

"We flew to a delta velocity threshold," said Kurt Eberly, Orbital ATK's Antares program manager, in a press briefing earlier this year. "When we hit that, we shut down the engines. We had a lot of fuel left in the tanks. Now, we're just going to move that threshold a little higher and burn more of the fuel in the first stage. At that point in the flight regime, the acceleration is pretty high because the stage is pretty light. Most of the propellant is gone, so you actually pick up quite a bit of performance by burning just a few more seconds into that propellant residual in the tanks."

With the higher performance, the upgraded Antares can carry approximately 300 pounds more cargo than managers initially expected. The lifting of additional conservative flight constraints, coupled with further minor changes to the vehicle, will further raise the Antares rocket's payload capacity another 300 pounds in the coming years.

Once the first stage finished its job on the OA-8 launch the Antares rocket's 12.8-foot-diameter (3.9-meter) diameter payload shroud will jettison in two halves at T+plus 4 minutes, 11 seconds. An interstage adapter that connected the first and second stages will separate at T+plus 4 minutes, 16 seconds.

The launcher's Castor 30XL solid-fueled upper stage will ignite at T+plus 4 minutes, 24 seconds, and generate up to 104,300 pounds of thrust during a burn lasting 2 minutes, 42 seconds. The second stage motor will burn out at T+plus 7 minutes, 6 seconds, then deploy the Cygnus spacecraft at T+plus 9 minutes, 6 seconds.

The spacecraft's two cymbal-shaped electricity-generating solar arrays will unfurl in a fan-like motion around 90 minutes into the mission, and the ship's thrusters will begin fine-tuning its approach to the space station with a series of course-correction burns Saturday and Sunday, setting up for a laser-guided final approach Monday.

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[tnt22]

11/11/2017 12:19

The Antares launch team is reshuffling steps in the countdown to allow a "red team" to deploy to pad 0A shortly to recharge the transporter-erector-launcher's hydraulic system. The launch team will defer hazardous operations, such as a test of the Antares destruct system, until the red team is finished with their work and departs the launch pad.

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11/11/2017 12:52

The red team has cleared the pad after troubleshooting the hydraulic system on the Antares rocket's transporter-erector-launcher.

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11/11/2017 12:57

With workers now safely away from the Antares rocket at pad 0A, the launch team is proceeding with testing of the flight termination system.

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11/11/2017 13:21

The launch team has completed internal power and arming tests on the flight termination system. The red team is about to return to the pad to finish work on the transporter-erector-launcher hydraulic system.

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ISS Updates‏ @ISS101 10 мин. назад

L-2 Hours: Setup for #Antares propellant loading is now in work by the launch team for prop flows at L-1:35. Second Mission Simulation Test started 12 minutes ago. Countdown now in a built-in hold.

11/11/2017 13:37

Two hours until launch. The Antares countdown is in a pre-planned hold, but the launch team is still targeting 7:37 a.m. EST (1237 GMT) for liftoff from pad 0A at the Mid-Atlantic Regional Spaceport on Virginia's Eastern Shore.

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ISS Updates‏ @ISS101 2 мин. назад

L-1 Hour 52 Minutes: The Red Team has departed the launch complex after final hands-on tasks were completed. Launch Team is working a communications issue. #Antares

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ISS Updates‏ @ISS101 1 мин назад

The Launch Weather Officer reported observed and forecast conditions are GO for launch. Cold temps are not an issue as #Antares is provided warm purge flow; the only problem would be an extended cold soak on the second stage.

11/11/2017 13:52

The latest briefing from the launch weather officer shows a 100 percent chance of acceptable conditions at launch time, with a few clouds, good visibility, northerly winds and cold temperatures.

The current temperature at Wallops Island is observed at 26 degrees Fahrenheit.

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ISS Updates‏ @ISS101 4 мин назад

Showing a constraint on the Nitrogen Purge System. Launch Team is working to reduce temperatures. Comm issue also still in work. #Antares

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11/11/2017 13:58

The countdown has resumed after a 20-minute built-in hold.

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Orbital ATK‏Подлинная учетная запись @OrbitalATK 53 сек. назад

L-1 hour and 37 minutes and we have GO for propellant loading. Weather is green with 0% probability of violation!

[tnt22]

Updated: 11/11/2017 14:01

Propellant will soon be pumped into the Antares rocket's first stage. About 21,000 gallons of RP-1, a high-refined rocket-grade kerosene, and about 41,000 gallons of liquid oxygen will be loaded into the first stage over the next half-hour.

Спойлер

The kerosene is stored at roughly room temperature and the liquid oxygen is chilled to around minus 298 degrees Fahrenheit. The oxygen will slowly boil off during the countdown, and liquid oxygen will continue flowing into the rocket until shortly before liftoff.

One change introduced by the Antares 230 rocket, which made its maiden flight in 2016, is the elimination of "sub-cooled" liquid oxygen chilled and densified at minus 383 degrees Fahrenheit for the Antares rocket's old AJ26 engines. The RD-181s consume the oxidizer at its boiling point.

The first stage tanks are designed by Yuzhnoye and built by Yuzhmash in Ukraine based on heritage from the Zenit rocket. The liquid oxygen tank is positioned in the upper part of the 12.8-foot-diameter stage and the RP-1 tank is in the lower part of the stage.

The first stage's two RD-181 engines will consume the liquid propellant during a 3-minute, 35-second burn.

The Antares second stage, a Castor 30XL motor built by Orbital ATK, is propelled by solid fuel already loaded into the rocket.

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[tnt22]

ISS Updates‏ @ISS101 45 сек назад

Confirmation that low-flow Rocket Propellant 1 load has begun as planned given by the launch team. #Antares

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[tnt22]

11/11/2017 14:08

Filling of the Ukrainian-built first stage with kerosene fuel has switched to high-flow mode. The start of liquid oxygen loading will come in the next few minutes.

NASA Wallops‏Подлинная учетная запись @NASA_Wallops 57 сек. назад

Fueling is underway for the @OrbitalATK Antares rocket. The launch window opens at 7:37 a.m. EST. #OA8 http://www.ustream.tv/channel/nasa-tv-wallops ...

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ISS Updates‏ @ISS101 2 мин. назад

Low-flow Liquid Oxygen loading has started on #Antares.

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ISS Updates‏ @ISS101 3 мин. назад

The Launch Team has resolved the Nitrogen purge temperature & TEL hydraulics issues. Telemetry is being kept in open loop as a workaround of another issue. Range & #Cygnus are GREEN, #Antares looking good at prop load start.

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Spaceflight Now‏ @SpaceflightNow 32 сек. назад

RP-1 kerosene and liquid oxygen are now both flowing into the Antares rocket's first stage. The launch team is not working any issues in the countdown at this time. https://spaceflightnow.com/2017/11/10/oa-8-mission-status-center/ ...