SpaceX F9 - WorldView Legion 1&2 - SLC-4E

Launch Date: May 2
Launch Window: 11:36AM PDT (2:36PM EDT, 18:36UTC)
Launch site: SLC-4E, Vandenberg Space Force Base, California
Core Booster Recovery: RTLS - LZ-4
Booster: B1051.20
Fairings: Reused
Mass: 8300 kg
Orbit: SSO
Yearly Launch Number: 45

A SpaceX Falcon 9 rocket will launch the first pair of WorldView Legion Earth observation satellites for Maxar Technologies. Maxar plans to deploy six commercial WorldView Legion high-resolution remote sensing satellites into a mix of sun-synchronous and mid-inclination orbits on three SpaceX Falcon 9 rockets. The first stage of the Falcon 9 will return to Landing Zone 4 at Vandenberg Space Force Base for landing.

 

[Grendal]

 

[Grendal]

https://twitter.com/x/status/1786099817187532954

 

[Grendal]

I recommend this launch to watch. Lots of interesting visuals. The payload had to be very light since they used the shorter nozzle, had the boostback for RTLS, while pushing the orbit out to 518 km.

 

[Ben W]

I recommend this launch to watch. Lots of interesting visuals. The payload had to be very light since they used the shorter nozzle, had the boostback for RTLS, while pushing the orbit out to 518 km.

Is the second stage expected to deorbit itself from 518km? (Or was it an elliptical transfer orbit?) I wonder what the record is for highest delta-V deorbit burn for a second stage. If the payload needs to circularize its orbit, presumably it makes more sense for the payload to use its own propulsion, rather than having the second stage do it. Besides the FH Roadster demo, how many Falcon second stages are still floating around up there?

 

[JB47394]

Besides the FH Roadster demo, how many Falcon second stages are still floating around up there?

I believe the norm for delivery to higher orbital altitudes is for the second stage to reach that altitude as its apogee, with the perigee low enough to encounter the tenuous layers of the atmosphere. The second stage continues orbiting, losing energy on each pass through perigee, and deorbits after 2-6 months.

For geostationary transfer orbit deliveries, the second stage continues on to a heliocentric orbit. This stackexchange post asserts that there are seven of those floating about, including the one with Elon's Roadster. I don't know if the second stage stays attached or if it stages and uses its remaining propellant to get separation. Or if it stages and allows the payload to go off on its own.

That same post asserts that there are 11 more launches planned that will leave second stages at heliocentric orbits. There are links for all sorts of stuff, and the post was last updated on April 4.

Note that a heliocentric orbit just means that the stage achieved Earth escape velocity, so now it's left to orbit the sun because it becomes the dominant body.

 

[Grendal]

Is the second stage expected to deorbit itself from 518km? (Or was it an elliptical transfer orbit?) I wonder what the record is for highest delta-V deorbit burn for a second stage. If the payload needs to circularize its orbit, presumably it makes more sense for the payload to use its own propulsion, rather than having the second stage do it. Besides the FH Roadster demo, how many Falcon second stages are still floating around up there?

Good question, and the answer is that I don't know. I'm sure there is some "objects in orbit" person that tracks all of them. I pretty sure there are only a few that will not eventually burn up in the atmosphere. I looked but couldn't find a list though.

 

[scaesare]

I recommend this launch to watch. Lots of interesting visuals. The payload had to be very light since they used the shorter nozzle, had the boostback for RTLS, while pushing the orbit out to 518 km.

Not sure I recall seeing that short nozzle before.

Given that in vacuum, the bigger the nozzle the better, is using a shorter one a way to decrease cost/mass/volume when not needed?

 

[JB47394]

Not sure I recall seeing that short nozzle before.

It was first used on the Transporter 7 mission (April 23, 2023), and has been used multiple times since. Here's a guy doing a short video about pros and cons of the shorter nozzle.

Short form is that it saves money when the extra performance of the full nozzle isn't needed. Second stages are expended, so there's no point in putting anything on them that isn't needed.

 

[Dave EV]

I recommend this launch to watch. Lots of interesting visuals. The payload had to be very light since they used the shorter nozzle, had the boostback for RTLS, while pushing the orbit out to 518 km.

It really sucks that SpaceX doesn't stream content on YouTube any more. Adding videos to my watchlist for later is the number #1 way I save content and that's not easily done on Twitter.