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1 minute ago, Xd the great said:

Yep, because apparently air force thinks the gps is so important that it should enjoy the luxury of an all-liquid booster launch.

They should procure a Fregat then. *trollface*

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Seriously, you’d think the nation that had built the Voyagers (which fired their thrusters this year) could manage to come up with a few long-lasting hypergolic tugs.

Although in context I do understand the issue. All of those late Soviet/Russian RBs began as supplemental upper stages for otherwise pretty anemic rockets. Fregat is an Earth escape stage, Volga is a refitted satellite propulsion bus, and Briz is the maneuvering upper stage of Naryad.

As I said, the United States had hydrolox for all their dV needs and then some.

Edited by DDE
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3 hours ago, DDE said:

Seriously, you’d think the nation that had built the Voyagers (which fired their thrusters this year) could manage to come up with a few long-lasting hypergolic tugs.

Although in context I do understand the issue. All of those late Soviet/Russian RBs began as supplemental upper stages for otherwise pretty anemic rockets. Fregat is an Earth escape stage, Volga is a refitted satellite propulsion bus, and Briz is the maneuvering upper stage of Naryad.

As I said, the United States had hydrolox for all their dV needs and then some.

Why would the nation built the Dawn (10km/s delta-v *after* hitting Earth escape velocity) want to use hypergolics on tugs (at least within Mars, possibly even to the asteroid belt)?  That said, it isn't like NASA (and DoD) contractors are all a monolithic bunch.

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41 minutes ago, wumpus said:

Why would the nation built the Dawn (10km/s delta-v *after* hitting Earth escape velocity) want to use hypergolics on tugs (at least within Mars, possibly even to the asteroid belt)?

Now that is a really good question. It'd probably be overkill as an expendable stage... but it doesn't have to be expendable.

I've heard of a solar-electric Russian tug design, but you can guess where that one went.

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15 hours ago, DDE said:

Seriously, you’d think the nation that had built the Voyagers (which fired their thrusters this year) could manage to come up with a few long-lasting hypergolic tugs.

We did have one back in the day, in the form of Agena. It was originally developed in the 50's for the WS-117 spysat program, but got co-opted into launching all sorts of other things, including the early Mariner and Ranger probes, and the Agena Target Vehicle used to develop docking tech during Project Gemini. Got used a few hundred times up through the late 80's, mostly for DoD payloads, before getting phased out in favor of various Delta upper stages and the Centaur/Star-(insert number here) combination. There was some talk in the early 2000's of building a new Agena variant as an upper stage for Atlas V for the EELV program, but nothing came of it. Shame, too - it was a nice upper stage.

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3 hours ago, IncongruousGoat said:

We did have one back in the day, in the form of Agena. It was originally developed in the 50's for the WS-117 spysat program, but got co-opted into launching all sorts of other things, including the early Mariner and Ranger probes, and the Agena Target Vehicle used to develop docking tech during Project Gemini. Got used a few hundred times up through the late 80's, mostly for DoD payloads, before getting phased out in favor of various Delta upper stages and the Centaur/Star-(insert number here) combination. There was some talk in the early 2000's of building a new Agena variant as an upper stage for Atlas V for the EELV program, but nothing came of it. Shame, too - it was a nice upper stage.

Electron’s grandma, too. The main engine used an electrically-driven pump.

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I could see the drive away from using hypergolics though. Partial insertion/circularization is done after a 6-ish hour coast, which isn't that long considering. According to this paper ULA experiences 1.0%-2.6% O2 boiloff per day. So I don't think that carrying the extra 0.5%ish of LOX would be as big of a performance hit as using a solid or hypergolic kick stage. Not to mention the added complexity of another staging event and hardware.

Even the fact that the second stage is way overpowered at that point, carrying a little extra fuel (if the tanks are big enough) for partial insertion/circularization would be worth it. 

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So there's a large tent structure set up at Boca Chica (open sided), and next to it is a heavy concrete circle... and on the concrete circle they are building (vertically) a steel tube. The tube has 3 openings at the bottom (large, but slot-like). The tube is, I dunno, 9m in diameter.

(control tower?)

Edited by tater
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1 hour ago, RealKerbal3x said:

I mean, obviously they're building a segment of the Starship outside, in the middle of a field :P

I think a movie started like this... and everybody laughed and then there was 40 days and 40 nights of meteor showers and no one was laughing anymore. But I could be mistaken. 

But they’re planning to build this in Florida:

5b1ae6cb1ae66251008b4b42-750-425.jpg

Does look a bit similar...

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1 hour ago, tater said:

So there's a large tent structure set up at Boca Chica (open sided), and next to it is a heavy concrete circle... and on the concrete circle they are building (vertically) a steel tube. The tube has 3 openings at the bottom (large, but slot-like). The tube is, I dunno, 9m in diameter.

(control tower?)

Landing tube for BFR? Probably not, I would guess the infrasound would be too much.

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Just now, Mad Rocket Scientist said:

Landing tube for BFR? Probably not, I would guess the infrasound would be too much.

I was actually thinking just an appropriate shape (and possibly mass) that they would literally use to test out a TE for attachment points, moving to a launch site, etc. I know they show it vertical all the time, but they have horizonatal facilities to build it, and ship it, they have to make it vertical at some point, and even if they have a crane, they'll want to test it.

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4 hours ago, Racescort666 said:

I could see the drive away from using hypergolics though. Partial insertion/circularization is done after a 6-ish hour coast, which isn't that long considering. According to this paper ULA experiences 1.0%-2.6% O2 boiloff per day. So I don't think that carrying the extra 0.5%ish of LOX would be as big of a performance hit as using a solid or hypergolic kick stage. Not to mention the added complexity of another staging event and hardware.

Even the fact that the second stage is way overpowered at that point, carrying a little extra fuel (if the tanks are big enough) for partial insertion/circularization would be worth it. 

There never was a need for them, strictly speaking. Block D was considered good for five days as the lunar orbit injection and lunar descent stage of the original mid-1960s N1-L3 manned landing stack; they lopped the insulation off later when it became an escape stage. The rest of the hypergolic tugs are mostly byproducts of other programs: Fregat and Volga have satellite bus heritage (Volga’s basically a post-Soviet Agena, a spysat bus, while Fregat is suspiciously similar to Ye-8 series of Luna probes), and Briz began as an ICBM-mounted ASAT stage.

Edited by DDE
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3 hours ago, RealKerbal3x said:

I mean, obviously they're building a segment of the Starship outside, in the middle of a field :P

Doesn't look like it could move...

A quick squirt of WD-40 will easily amend that. Seriously, if its moving and it's not supposed to move, use duct tape. If it's not moving and it's supposed to move, used WD-40.

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