Firefly stops second launch attempt due to weather

Aiming to reach orbit successfully, Firefly is set to launch FLTA002 – the second test flight of the Alpha launch vehicle – on the mission dubbed “To The Black”. Departing from Space Launch Complex 2 West (SLC-2W) at Vandenberg Space Force Base in California, the craft is now scheduled to lift off no later than September 19 in a window from 3:00 to 7:00 p.m. PT (22): 00 to 02:00 UTC).

Sunday’s launch attempt was called off after aborting less than a minute before the window opened and subsequent delays throughout the window. The teams then withdrew from another opportunity on Monday due to the weather.

FLTA002 will attempt to place several small satellites into a 300 km circular low Earth orbit (LEO) with an inclination of 137 degrees.

Firefly’s first orbital launch attempt During the first stage of the burn on September 3, 2021, after an engine failure 14 seconds after launch. Despite the engine being turned off, the car was able to maintain control for about two and a half minutes, before getting stuck, prompting the ground operators to activate the trip termination system.

Firefly was able to restore the engine assembly down the range, letting them know that the engine had stalled early due to a failure of the bolts in the power line to the engine’s main valves, causing them to shut off and the engine to shut down. This malfunction mode was backed up with data from the vehicle, which reported a current drop on the power rail and valve shutdown.

Tom Markusick, founder of Firefly, noted that Flight 1’s engines were “harsher” than newer engines, and therefore produced more vibrations during flight. However, to be safe, the teams have moved the electrical connector up into the car where the vibrations are less severe, ensuring that the same fault situation is not repeated.

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Alpha is a small, two-stage launch vehicle built and developed by Firefly Aerospace. With the ultimate goal of being able to carry 1,170 kg of payload into LEO, the vehicle stands at an altitude of 29.48 meters. Alpha has much more mass in orbit than other small satellite launchers, such as the Electron Rocket Lab or Astra 3 . missile which showed the placement of up to 300 kg and 25 kg into LEO, respectively.

The first stage of the Alpha is equipped with four Reaver 1 engines, which run on RP-1 kerosene and liquid oxygen (LOX). Notably, the Reaver uses the engine cycle, which means that instead of having a separate gas generator to spin the turbines, pressure from the main combustion chamber is used. However, since the exhaust gas used to spin the turbine is still exhausted, this engine is still considered an open-cycle engine.

Each Reaver engine produces a maximum thrust of 200 kN and achieves a specific thrust of 296 seconds in the vacuum of space. For rocket engines, the specific thrust of the engine is directly proportional to the velocity of the exhaust gas; For the Reaver, the maximum average exhaust velocity is around 2,900 m/s.

Both the first and second Alpha stages are built from carbon fiber composites that form ultra-light propellant tanks without a liner. Similar to the Falcon 9, both stages have RP-1 tanks on the bottom with a LOX tank on top, with a transfer tube for delivering LOX to the motors.

FLTA002 vertically in SLC-2W prior to launch. (credit: Michael Baylor to NSF)

The second stage is equipped with a single Lightning 1 motor, which is also a starting motor cycle capable of producing 70 Newtons of thrust.

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At the top of the second stage lies the carbon composite payload streamline. For “To The Black” there are a number of small loads inside. First, educators in space will launch the Serenity 3U CubeSat, which will collect flight data during its mission and make it available to the education community.

Also flying on FLTA002 is a NASA TES-15 3U CubeSat aircraft, which has a deployable external brake that will be used to validate the CMS for future re-entry. This payload is part of NASA educational satellite technology The program that gives students the opportunity to work on satellites.

The final payload will be the Libre Space Foundation’s PicoBus, which will deploy six pico satellites. All of these satellites are technology offerings for communications, remote sensing, and more.

Eight hours before launch, teams will begin performing final pad checks. During this time, the Alpha will be running and performing sensor checks, which should be completed by T-6 hours. At this point, the vehicle will begin to be loaded with helium, which is used to pressurize and refill the tanks as they are emptied during ascent.

At T-5 hours and 15 minutes, it will start loading the car with RP-1. After 45 minutes, the pad will be flushed, giving way to starting LOX loading at T-3 hours and 40 minutes. The fuel loading will continue until 20 minutes before launch when the vehicle enters the final count. At this point, the missile will be fully refueled (with both RP-1 and LOX), and will remain covered with both thrusters.

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The Reaver 1’s four first-stage engines will ignite at T-1.8 seconds using TEA-TEB – a flammable compound, meaning it burns on contact with oxygen. This combustion will be light green and will indicate the engines are starting. Assuming all four engines and the vehicle are nominal, the release clamps will release from the base of the vehicle, allowing it to launch.

At T + 1: 13 the car will pass through maximum aerodynamic pressure. At T+2:37, the four first stage motors will shut down, in an event called Main Engine Cut Off (MECO), before the stages separate and the second stage ignites its motor.

Less than a minute later, at T+3:25, the streamlining will be deployed. The second stage will then burn for another four minutes, before closing at T+7:40. However, at this point, the job is not over, as the stage will continue until T+53:57 when the engine fires for a second time, this time for two seconds. . This will raise the initial elliptical orbit to a circular orbit with a length of 300 km.

Alpha will then deploy all three payloads, to finish its mission at T+1:01:57.

If the mission is successful, Firefly hopes to launch in late 2022 FLTA003, which will likely be NASA’s ELaNa 43 mission.

(Main image: FLTA002 on stage before launch. Credit: Jack Beyer for NSF)

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