Firefly withdraws from second launch attempt due to weather

Firefly withdraws from second launch attempt due to weather
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With the goal of successfully reaching orbit, Firefly is set to launch FLTA002, its second Alpha Launch Vehicle demonstration flight, on the mission dubbed “To The Black.” Launched from Space Launch Complex 2 West (SLC-2W) at Vandenberg Space Force Base in California, the vehicle is now scheduled to take off no earlier than September 1. 19 in a window from 3:00 to 7:00 pm PDT (22:00 to 02:00 UTC).

A launch attempt was removed on Sunday following an abort less than a minute before the window opened and subsequent delays throughout the window. The teams then pulled out of another shot on Monday due to 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 it ended during the burning of the first stage on September 1. January 3, 2021, following engine failure 14 seconds after launch. Despite this engine shutdown, the vehicle was able to maintain control for almost two and a half minutes, before going down, prompting ground operators to activate the flight termination system.

Firefly was able to recover the lower range of the engine assembly, allowing them to realize that the engine shut down prematurely due to failed pins in the feed line to the engine’s main valves, causing them to close. and turn off the engine. This failure mode was supported by data received from the vehicle, which reported a drop in current in the power rail and valve closure.

Firefly founder Tom Markusic noted that the Flight 1 engines were “harder” than newer engines and therefore produced more vibrations during flight. However, to be on the safe side, the teams moved the electrical conductor further up the vehicle where the vibrations are less intense, ensuring that the failure mode does not repeat itself.

Alpha is a two-stage small-lift launch vehicle built and developed by Firefly Aerospace. With the ultimate goal of being able to place 1,170 kg of payload on LEO, the vehicle has a height of 29.48 meters. Alpha has a significantly higher mass to orbit than other small satellite launchers, such as Rocket Lab Electron either astra Rocket 3, they have been shown to place up to 300 kg and 25 kg in LEO, respectively.

Alpha’s first stage is equipped with four Reaver 1 engines, running on RP-1 kerosene and liquid oxygen (LOX). In particular, Reaver uses the bypass engine cycle, which means instead of having a separate gas generator to spin the turbines, pressure from the main combustion chamber is used. However, as the exhaust gas used to spin the turbine is still used up, it is still considered an open cycle engine.

Each Reaver engine produces a maximum thrust of 200 kN and achieves a specific impulse of 296 seconds in the vacuum of space. for rocket engines, the specific impulse of the engine is directly proportional to the velocity of the exhaust gases; for Reaver, the maximum average escape velocity is ~2900 m/s.

Alpha’s first and second stages are constructed of carbon fiber composites that form ultra-light, unlined propellant tanks. Similar to the Falcon 9, both stages have their RP-1 tanks on the bottom with the LOX tank on top, with a transfer tube to deliver LOX to the engines.

Vertical FLTA002 on SLC-2W prior to launch. (Credit: Michael Baylor for NSF)

The second stage is powered by a single Lightning 1 engine, which is also a derivative engine cycle capable of producing 70 N of thrust.

On top of the second stage is the carbon composite payload fairing. For “To The Black”, there are a number of small payloads inside. First, Teachers in Space will launch the Serenity 3U CubeSat, which will collect flight data during its mission and make it available to the educational community.

Also flying on FLTA002 is NASA’s TES-15 3U CubeSat, which has a deployable exobrake that will be used to validate center-of-mass systems for future re-entries. This payload is part of NASA Satellite Educational Technology program, which gives students the opportunity to work on satellites.

The final payload will be Libre Space Foundation’s PicoBus, which will deploy six picosatellites. All of these satellites are technology demonstrators for communication, remote sensing, and more.

Eight hours before launch, the teams will begin final checks of the platforms. During this time, the Alpha vehicle will power up and perform sensor checks, which must be completed by T-6 hours. At this point, the vehicle will begin charging with helium, which is used to pressurize and refill the tanks as they empty during the ascent.

At T-5 hours and 15 minutes, the vehicle will begin to be loaded with RP-1. 45 minutes later, the platform will clear, ushering in the start of LOX loading at T-3 hours and 40 minutes. The propellant charge will last until 20 minutes before launch, when the vehicle will enter terminal countdown. At this point, the rocket will be fully fueled (with both RP-1 and LOX) and will be continuously refueled with both boosters.

The four Reaver 1 engines in the first stage will ignite in T-1.8 seconds using TEA-TEB, a pyrophoric compound, meaning it burns on contact with oxygen. This combustion will be bright green and will signal the start of the engines. Assuming all four motors and the vehicle are rated, the launch clamps will release from the base of the vehicle, allowing it to lift.

At T+1:13 the car will go through maximum aerodynamic pressure. At T+2:37, all four first stage engines will shut down, in an event called main engine cut-off (MECO), before the stages separate and the second stage fires its engine.

Less than a minute later, at T+3:25, the fairing will be deployed. The second stage will then burn for another four minutes, before shutting down at T+7:40. However, at this point the mission is not over, as the stage will slide to T+53:57 when the engine will fire a second time, this time for two seconds. This will raise the initial elliptical orbit to a 300 km circular orbit.

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

Should the mission be successful, Firefly hopes to launch FLTA003 in late 2022, which will likely be the ELaNa 43 mission for NASA.

(Lead photo: FLTA002 on the pad before launch. Credit: Jack Beyer for NSF)

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