STP-27AD1 | Astra Rocket 3

Featured image credit: Astra / John Kraus

Lift Off Time	August 28, 2021 – 22:35 UTC | 15:35 PDT
Mission Name	STP-27AD1, a mass simulator
Launch Provider (What rocket company launched it?)	Astra
Customer (Who paid for this?)	U.S. Space Force
Rocket	Rocket 3.3 – LV0006
Launch Location	Launch Pad 3B, Pacific Spaceport Complex in Kodiak, Alaska
Payload mass	Unknown, up to 25 kg (55 lb) (based on previous Rocket 3s)
Where was the payload supposed to go?	To a 415 km low Earth Orbit (LEO) at 70° inclination
Did they attempt to recover the first stage?	No, this is not a capability of Astra
Where did the first stage land?	The whole rocket crashed into the Pacific Ocean
Did they attempt to recover the fairings?	No, this is not a capability of Astra
Were these fairings new?	Yes
This was the:	– 1st launch attempt for Astra in 2021 – 1st commercial launch for Astra – 3rd launch of an Astra Rocket 3 – 5th failure of a launch vehicle in 2021
Where to re-watch	NASA Spaceflight’s official livestream Live updates on Astra’s Twitter account

How Did It Go?

Astra attempted to launch its first commercial payload to space on its Rocket 3.3 otherwise known as LV0006 (Launch Vehicle 0006). STP-27AD1 was one of two test launches for the Department of Defense (DoD) as part of the Space Test Program (STP) of the U.S. Space Force. Fireing up its engines at Launch Pad 3B at the Pacific Spaceport Complex in Kodiak, Alaska, Rocket 3.3 was only Astra’s 3rd attempt at reaching orbit.

LV0006 successfully ignited all of its 5 Delphin engines at T-3 s, but, unfortunately, lost one of its engines less than a second into flight. Engine shut down occurred approximately 0.3 s after the hold down clamps released. As a result of that engine failure, the whole rocket tilted into the direction of the failed engine. Miraculously, the guidance system and the four remaining engines were able to compensate for the lost engine and kept the vehicle upright.

With the thrust-to-weight ratio (TWR) dropping from 1.25:1 to 1:1, the rocket, conserving the momentum induced by the earlier tilt, did a powerslide away from launch structure. For several seconds the vehicle moved sideways away from the launch pad before burning off enough propellant to start its slow ascent. The teams at Astra got 2 minutes and 31 seconds of flight data before the range terminated the flight by sending out an all engine shut down command as the vehicle was unable to fly its planned trajectory at this point due to the engine failure. Rocket 3.3 continued costing up to around 50 km and later safely splashed down in the Pacific Ocean.

The teams at Astra are extremely proud of their guidance system for keeping the vehicle stable and that it achieved what it did achieve, despite the early engine failure. Astra will now go through the loads of data they have recorded and will share more information as it becomes available. In a statement right after the loss of the vehicle, Chris Kemp, CEO of Astra, can be seen standing in front of LV0007, Astra’s next launch vehicle. LV0007 is at a stage of production where changes can easily be integrated, hoping to get back to the launch pad soon.

STP-27AD1

Due to the classified nature of the program, not much is known about the plans the DoD has for these missions. STP-27AD1 was a mass simulator in order for Astra and the DoD to validate Rocket 3.3’s capabilities. This was the first of two planned missions flying on Astra’s Rocket 3. The second one, STP-27AD2, was planned to launch later this year. The DoD’s Space Test Program provides flight opportunities for test and experimental payloads.

Mission Timeline*

HH:MM:SS From Lift Off	Events
T-01:15:00	Start of pre-launch procedure
T-00:45:00	Propellant load begins
T-00:20:00	Propellant load complete
~T-00:15:00	Water deluge system test
T-00:15:00	Entering terminal count
T-00:03:00	Ignition!
T+-00:00:00	Lift Off!
T+00:00:12	Begin Pitch Over
T+00:01:15	MaxQ
T+00:02:50	Main Engine Cut Off (MECO)
T+00:02:55	Fairing separation
T+00:03:00	Stage separation
T+00:03:05	Second stage ignition
T+00:08:20	Second Engine Cut Off (SECO)
T+00:08:30	Payload deployment signal

*Timeline of a nominal launch

Astra’s Rocket 3.3 – LV0006

This Rocket 3, also known as LV0006, was Astra’s fourth iteration of their third version of their small-sat launch vehicle. The Rocket 3 series is Astra’s orbital rocket series with LV0006 being ready for launch after its successful static fire on August 04, 2021. With a height of 13.1 m (43 ft), a diameter of 1.32 m (4.3 ft) and a payload capacity of 25 kg to a 500 km Sun-Synchronous Orbit (SSO)**, it is in the same class of small-sat launch vehicles as Rocket Lab’s Electron.

This two-stage rocket is powered by RP-1 and LOx. The first stage will make use of five electric-pump-fed Delphin engines that will produce a total thrust of ~145 kN (~32,500 lbf) at liftoff. The second stage is powered by a single pressure-fed Aether engine that will produce ~3.3 kN (740 lbf) of thrust in a vacuum. Since Astra is a rather secretive company, they have not released any technical information about their engines, such as ISP (Specific Impulse), TWR (Thrust to Weight Ratio), or combustion chamber pressure. The aluminum body and tanks of Rocket 3 have some similarities to SpaceX’s Starships, with its welded stacked rings of stainless steel.

Rocket 3.3	1st Stage	2nd Stage
Engine	Delphin	Aether
# of engines	5	1
Thrust per engine	~29 kN	~3.3 kN
Total thrust	~145 kN	~3.3 kN
Engine cycle type	Electric-pump-fed	pressure-fed

Another unique characteristic is that Astra’s Rocket 3 series rockets fit into a standard shipping container and can be towed by a truck. To set up the rocket on its mobile launch structure, it only takes a handful of ground support staff and about a week to go through vehicle checks, a wet dress rehearsal, and the launch readiness review. Astra’s goal for the future is to bring the time required to set up the rocket down to under 24 hours, so that it can meet the needs of some special customers who require a rapid launch schedule for their payloads.

**based on previous Rocket 3s

Differences To Earlier Rocket 3 Series Rockets

Astra have upgraded their series 3 rockets launch after launch, and the same is true for this rocket too. It is not exactly known what those upgrades are other than an update to the fuel and oxidizer mixture of the rocket’s second stage. Furthermore, Chris Kemp, CEO of Astra, has stated in an interview with NASA Spaceflight that they have stretched the first stage for more performance.

Earlier Losses

Astra has launched two orbital class rockets in an attempt to reach orbit. So far, all of these launches have failed to achieve orbit, with the latest, Rocket 3.2, just barely missing orbit by about 500 m/s. Its second stage safely re-entered before completing one full rotation of Earth.

• Rocket 3.0: loss of the vehicle during ground testing due to a stuck open valve while detanking the vehicle.
• Rocket 3.1: FTS activated 21s into flight due to a software issue in the guidance system.
• Rocket 3.2: Rocket 3.2 failed to achieve orbit by ~500 m/s due to a wrong mixture of fuel and oxidizer on the second stage.

Astra is confident to reach orbit this time, as it had to only change the fuel/oxidizer mixture slightly to achieve a more efficient burn that will result in reaching orbit.