STP-27AD2 | Astra Rocket 3.3

Launch Window
(Subject to change)
November 20, 2021 – 06:16 UTC
November 19, 2021 – 22:16 PST
Mission Name
STP-27AD2, a test payload for the U.S. Space Force
Launch Provider
(What rocket company is launching it?)
(Who’s paying for this?)
U.S. Space Force
Rocket 3.3 – LV0007
Launch Location
Launch Pad 3B, Pacific Spaceport Complex in Kodiak, Alaska
Payload mass
Unknown, it is a non-deployable test payload
Where is the payload going?
To a 500km low Earth orbit (LEO) at 86° inclination
Will they be attempting to recover the first stage?
No, this is not a capability of Astra
Where will the first stage land?
The first stage will crash into the Pacific Ocean
Will they be attempting to recover the fairings?
No, this is not a capability of Astra
Are these fairings new?
How’s the weather looking?
Live weather updates can be accessed here
This will be the:
– 2nd launch for Astra in 2021
– 2nd commercial launch for Astra
– 4th launch of an Astra Rocket 3
– 114th orbital launch attempt of 2021
Where to watch
NASA Spaceflight’s official livestream

Live updates on Astra’s Twitter account

What Does All This Mean?

Astra is launching its next payload to space on its Rocket 3.3. STP-27AD2 is the second of two test launches for the Department of Defense (DoD) as part of the Space Test Program (STP) of the U.S. Space Force. Taking off to the skies from Launch Pad 3B at the Pacific Spaceport Complex in Kodiak, Alaska, Rocket 3.3 will only be Astra’s 4th attempt at reaching orbit.

This article will be updated as more information becomes available.


Due to the classified nature of the program, not much is known about the plans the DoD has for these missions. STP-27AD2 is a non-deployable mass simulator with sensors like STP-27AD1, which will allow Astra and the DoD to validate Rocket 3’s capability. What we know so far is that this is the second of two planned missions flying on Astra’s Rocket 3. The first one, STP-27AD1, failed to reach orbit after an engine on the first stage failed less than a second after ignition. The DoD’s Space Test Program provides flight opportunities for test and experimental payloads.

Mission Timeline*

From Lift Off
T-01:15:00Start of pre-launch procedure
T-00:45:00Propellant load begins
T-00:20:00Propellant load complete
T-00:15:00Entering terminal count
T-00:15:00Water deluge system test
T+-00:00:00Lift Off!
T+00:00:06Begin Pitch Over
T+00:02:50Main Engine Cut Off (MECO)
T+00:02:55Fairing separation
T+00:03:00Stage separation
T+00:03:05Second stage ignition
T+00:08:30Second Engine Cut Off (SECO)
T+00:08:40Payload deployment signal
*pre ignition events are approximate

Astra’s Rocket 3*

This Rocket 3, also known as LV0007, will be Astra’s fifth iteration of the third version of their small-sat launch vehicle. The Rocket 3 series is Astra’s orbital rocket series with LV0007 being their 7th rocket overall. With a height of 13.1 m (43 ft), a diameter of 1.32 m (4.3 ft), and a payload capacity of approximately 50 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.

Rocket 3.2, lift off, Astra
Rocket 3.2 during shortly after lift off from Pad 3B. (Credit: Astra/John Kraus)

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.

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.

*Information based on the press kit of Astra’s launch of LV0007

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. After the failed flight of LV0006, Astra implemented following changes to ensure a successful flight:

  • Reconfiguration of their propellant supply system to prevent mixing of fuel and oxidizer in case of a leak.
  • Modification of the propellant supply mechanism to reduce the risk of leaks.
  • Verification procedures have been improved for design and operational processes.

Furthermore, Chris Kemp, CEO of Astra, has stated in an interview with NASA Spaceflight that going from LV0005 to LV0006, they have stretched the first stage tanks for more performance.

Rocket 3.2 vs. Rocket 3.3 LV0006, Astra
Astra’s Rocket 3.2 next to Rocket 3.3 LV0006. (Credit: Stanley Creative)

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.
  • Rocket 3.3: LV0006 was terminated at T+2:31 after one of the engines experienced a failure less than 1s after ignition due to the ignition of leaking fuel and oxidizer in the propellant supply system, better known as a quick disconnect, at the base of the rocket.

Astra is confident about reaching orbit this time, as it has implemented changes to prevent any similar failures to happen.

Video clip of Astra’s LV0006 launch and failure of its quick disconnect system, resulting in the loss of one engine. (Credit: Footage provided by NASASpaceflight LLC and Astra Space Inc.)
  1. We do know that each Delphin engine has a thrust to weight ratio of 1:4 (.25:1) since LV0006 was hovering and thus, had a thrust to weight ratio of 1:1 so each engine had a TWR 1:4.

    1. If you refer to the TWR of the rocket, then yes, it would be around 1:4 per engine, but when talking about rocket engines you usually compare the TWR of the engine itself. So this would be the thrust to engine weight ratio. For example the Merlin engines have a TWR of about 200:1.

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