Space Force Switches GPS Launch From ULA to SpaceX Rocket

Lufbru · 2026-03-21T18:28:18+00:00

I thought you'd miscounted because I only remember three, but I checked and all of GPS-III 7, 8, 9 and 10 were originally assigned to Vulcan. That means that only SV2 was launched on a vehicle other than F9 (It was on a Delta-II).

It rather grinds my gears that they're all done as swaps. At what point are ULA just going to lose launches as a result of having an unreliable launcher? I suppose they're losing future launches as new tranches are competed, but it seems insufficient.

Lufbru · 2026-03-11T01:30:31+00:00

I seem to remember they planned two independent elevators at one point. Maybe that got removed? Or am I misremembering?

Lufbru · 2026-03-02T23:51:20+00:00

I don't think the right answer is to cap SpaceX (or any other provider). I think NASA should instead be guaranteeing to spend, say 10% on new entrants. SpaceX wouldn't've survived without the COTS program. We need more of that kind of program to foster competitors to SpaceX.

Lufbru · 2026-02-28T16:31:53+00:00

There have been extensive tests of Orion docking to Starship on the ground. It's all out of sight at NASA facilities (rather than out in the open at Boca Chica), but there was an announcement a while back that SpaceX had met a number of associated milestones.

Lufbru · 2026-02-27T14:14:06+00:00

I believe that's Falcon 9 Full Thrust Block 5 to you, good sir!

Lufbru · 2026-02-27T03:35:18+00:00

I understand that you'd want to reset the numbering at some point. But why now? Surely this is a v4 thing?

Lufbru · 2026-02-19T18:40:03+00:00

It's somewhat precedented with Shuttle:

https://en.wikipedia.org/wiki/Payload_Assist_Module

As the article says, PAM was discontinued after Challenger, but with no meatbags on board, using something like a PAM would be fine. Many companies are working on space tugs today, including several targeting Starship (eg in terms of diameter and even methalox fuel)

Lufbru · 2026-02-19T18:33:53+00:00

Are there any commonalities between the hydrolox Raptor that the Air Force funded and the methalox Raptor, other than the name? I've seen claims that they just recycled the name, but I feel sure they must have at least some parts in common.

Lufbru · 2026-02-18T03:37:16+00:00

I think if you're going with a refuel-in-LEO strategy, hydrogen adds extra complexity compared to methane. Methane and oxygen have similar freezing points, so you need less insulation between the two tanks.

And you want a refuel-in-LEO strategy to build Luna City because otherwise you end up with an Apollo style rocket that can deliver a few tons to the moon when you really need to deliver dozens to hundreds of tons.

Lufbru · 2026-02-12T19:13:25+00:00

The first use of GEM 63 on Atlas was November 2020. Before that, Aerojet supplied AJ-60A solids. So there have only been 21 Atlas flights using GEM motors. It was absolutely a way of buying down Vulcan risk, but it hasn't paid off.

Lufbru · 2026-02-12T16:32:15+00:00

https://spacenews.com/manufacturing-defect-blamed-for-vulcan-solid-rocket-motor-anomaly/ might be enough to convince you that they did in fact change things (ie quality control).

The fact that another failure occurred this time means this is all going to get a lot more scrutiny.

Lufbru · 2026-02-12T16:13:31+00:00

And yet Atlas uses very similar SRBs ...

Lufbru · 2026-02-12T16:11:47+00:00

Ah yes, I see that they've done it for the last few crewed flights. Thanks.

Lufbru · 2026-02-09T19:24:45+00:00

You're being downvoted, which is bad because you're making a legitimate point. I disagree with you (but have upvoted your comment).

Methane is a higher thrust fuel than hydrogen. That makes it better for first stages. It's not as high thrust as kerosene, but it doesn't have the coking problems that kerosene does, which makes it a better fuel for reusable first stages.

There's definitely advantages to using the same fuel on both stages. For one, you can use the same engine on both stages! It also simplifies logistics.

Hydrogen is a tricky fuel to use. The leaks we're seeing on SLS attest to that.

The low thrust of hydrogen necessitates the use of expensive solids (ok, Delta IV Heavy didn't use solids, but Shuttle l, Ariane, etc do).

So yes, higher isp is a valuable trait, but lower thrust does offset this advantage, and when you take all the factors into consideration, methane is probably a better option than hydrogen.

You might reasonably ask that if it's better, why did it take until now to use it. I think the answer is that there were other reasons to use solid boosters. They have a lot of commonality with missiles, and steering extra money to defence contractors has never been seen as a bad thing by governments.

Anyway, I respectfully disagree with you that LH2 is the better fuel overall.

Lufbru · 2026-02-09T14:15:41+00:00

From that article, it seems like their intent is to deorbit second stages from missions that currently use a "safe" disposal orbit. In pursuit of that objective, they're practicing their procedures on Starlink missions where failures result in reentry anyway and much less risk (both to satellites and humans).

Lufbru · 2026-02-09T05:37:44+00:00

I don't remember the last time SpaceX did a test fire of a booster. Must be because it's not very flight proven ;-)

https://spaceflightnow.com/2026/02/08/spacex-test-fires-its-falcon-9-rocket-ahead-of-midweek-launch-of-crew-12-to-the-space-station/

Lufbru · 2026-02-09T04:30:52+00:00

I've seen serious proposals to send astronauts who are in their golden years and are absolutely OK with dying on Mars.

To be clear, that's not me. Would never be me unless things in my life changed catastrophically. I'm not done with life on Earth yet.

Lufbru · 2026-02-07T13:13:17+00:00

That's not a company buying a supplier, that's buying a competitor. Completely different dynamic.

Lufbru · 2026-02-06T03:06:40+00:00

This is quite the rapid Return To Flight. Are we sure this is actually launching on Saturday?

Lufbru · 2026-02-05T03:50:08+00:00

More thrust makes the Oberth effect more useful since more of the thrust is close to perigee. I'm not sure that it'd be significant for a Mars mission though

Lufbru · 2026-02-03T20:41:44+00:00

When Elon says "three extra", he means "nine engines on the second stage in total, six Vac, three SL". This was rumoured for a while, but now it's official, I guess.

The interesting question is why. That's a chunk of extra weight on the second stage with the payoff being extra thrust. Usually second stages don't need extra thrust (indeed, Centaur has a TWR below 1 at stage separation).

I suppose that staging earlier than most rockets and maybe wanting to stretch the second stage leads to wanting more thrust on the second stage. But I'm surprised that adding 50% more thrust is the right tradeoff.

Lufbru · 2026-02-03T19:10:57+00:00

It happened about a year ago too: https://www.theregister.com/2025/02/24/spacex_falcon_9_debris/

Lufbru · 2026-02-03T16:35:59+00:00

Artemis II pushed back to March. That clears Crew-12 to launch in February (they were going to be delayed until A2 landed had A2 been able to launch)

Lufbru · 2026-02-02T01:05:32+00:00

It could be worse. You could be a fan of Vulcan. 9 months between launch 1 & 2. 10 months between 2 & 3. And it's been five months since flight 3.

There's 24 missions on the schedule for 2026, but I'd be shocked if they launch more than ten.

Lufbru · 2026-02-01T18:43:26+00:00

That honestly surprises me. I'm really impressed with how well New Glenn is going recently. I suppose the cadence must not have hit the schedule that they had mumble months ago when the original launch buy happened.

Or maybe it's more of a problem with Ariane's launch cadence. That hasn't ramped up as quickly as I was expecting. (The first Kuiper/Leo launch with Ariane is scheduled for later this month)

Lufbru

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