Atlas V 411 - Just why ?

[Gaarst]

Here is a picture of an Atlas V 411 rocket:

Do you notice anything wierd ? Like a missing booster for example... And no that booster did not fall off the rocket, it wasn't even there to begin with !

So I need an explanation here: what is the point of making an asymmetric rocket ? Who thought that was a good idea ? And in what aspects is it better than making a rocket able to properly fly upwards ?

I mean, even if thrust is still towards the centre of mass, the rocket would have to fly sideways. And I know that one booster is cheaper than two, but wouldn't it be simpler to just put two of these and launch the thing straight up instead of having some over-complicated gimballing or trajectory control to avoid too strong aerodynamic forces ?

If anyone has an idea why this is a thing, I'd be more than happy to hear it !

EDIT:

Thanks to pTrevTrevs' comment, I extended my question to all Atlas V configurations, even with more than one booster:

EDIT2:

After a bit of searching I found that all Atlas V boosters are arranged asymmetrically because of the first stage core arrangement: there is "stuff" (LOx feedline and avionics pod) on the exterior of the tank that prevents boosters from being attached symmetrically (can actually be seen on the picture above).

Edited October 11, 2015 by Gaarst
Added possible solution

[Sampa]

oddly weighted payloads?

[Columbia]

Based on a quote I saw a few years back:

Because why not?

In all seriousness, I believe it's for cost, but the cosine losses..

[Flymetothemun]

2 boosters, too much power, no boosters, too little power?

[Gaarst]

2 boosters, too much power, no boosters, too little power?

Yes, I guess that 1 booster allows for a mass to orbit smaller than 2, but bigger than 0; but wasn't there really any other solution to save the payload difference ?

[G'th]

We could probably shed more light on the why if we knew which launch this was.

[pTrevTrevs]

Well, none of the booster configurations for the Atlas V are symmetrical anyway, maybe the designers did it just to show off their mad skills in engineering or something.

[sp1989]

I gotta admit that rocket does look awkward lifting off.

[Dodgey]

Why? Because they didn't need the power of two boosters, why waste money on a second one when you only need one?

[Gaarst]

We could probably shed more light on the why if we knew which launch this was.

There have been 3 Atlas V 411 launches so far:

- A 4t satellite put to GEO (Astra 1KR) (the one on the picture according to the image source)

- A shady reconnaissance satellite in Molynia orbit (USA 200)

- A pair of more shady reconnaissance satellites in LEO (USA 229 and USA 229-2) possibly called Intruder 9A and 9B (not going to comment on the names...)

Well' date=' none of the booster configurations for the Atlas V are symmetrical anyway, maybe the designers did it just to show off their mad skills in engineering or something.[/quote']

I never actually thought about that but you're right !

Here's what I found on Atlas V booster configurations: (same source, didn't make it on purpose)

Well, seems my initial wonder is extended to the whole Atlas V series...

- - - Updated - - -

Why? Because they didn't need the power of two boosters, why waste money on a second one when you only need one?

I agree with this, but on my latest post, there is a picture which shows asymmetric configurations for more than 1 booster.

So that doesn't answer my question: why so asymmetric ?

[sp1989]

The first Atlas V ever launched was a 411

[Gaarst]

The first Atlas V ever launched was a 411

Nope, first Atlas V launched was a 401 (no booster) on 21st August 2002.

First 411 was launched in 2006.

[Dodgey]

To avoid structural elements on the outside of the rocket, if you look at that diagram you will see some sort of structure on the outside that the boosters have to avoid.

[Bill Phil]

The gimbal range is very large on the RD-180.

[sp1989]

Nope, first Atlas V launched was a 401 (no booster) on 21st August 2002.

First 411 was launched in 2006.

Sorry I read it wrong. The 411 iteration was the first Atlas V ever launched from Vandenberg.

[regex]

The gimbal range is very large on the RD-180.

And it owns. Just let that sink in. It owns.

[lajoswinkler]

And it owns. Just let that sink in. It owns.

What does it want this time?

[pTrevTrevs]

I never actually thought about that but you're right !

Here's what I found on Atlas V booster configurations: (same source, didn't make it on purpose)

http://space.skyrocket.de/img_lau/atlas-5_config.png

Well, seems my initial wonder is extended to the whole Atlas V series...

Look, even on the configurations with an even number of boosters, the arrangement is deliberately asymmetrical. The only reason I can think of for this is that the designers just wanted to show off.

Maybe the Delta IV team made a bet with the Atlas V guys or something. If they did, I hope the Atlas V team got something good out of it, they deserve it.

[Bill Phil]

I think it had to do with the fact that they never really intended the design to have SRBs, but then that became a requirement, after they had already designed the stage. So, instead of a complete redesign, they put the SRBs where they could go.

Although, if they intended it to have SRBs, then, I can't really guess.

[pTrevTrevs]

I think it had to do with the fact that they never really intended the design to have SRBs, but then that became a requirement, after they had already designed the stage. So, instead of a complete redesign, they put the SRBs where they could go.

Although, if they intended it to have SRBs, then, I can't really guess.

Of course, it isn't that hard to modify a rocket stage to feature SRBs. Except for fuel lines, the side is pretty empty, so there should be plenty of places to attach SRBs in a symmetrical arrangement, especially if there are only two or three

[LordFerret]

I gotta admit that rocket does look awkward lifting off.

And I have to admit that launch was a hell of a lot smoother than a lot of my launches - even with symmetrical builds. They went to space. Time for me to go finish my current endeavor and see if I can claim the same lol.

[mythbusters844]

What does it want this time?

Unmatched reliability, with over 50 successful launches, which really isn't surprising for a company that places results over rhetoric and is the supreme launch provider of the world.

Edited October 11, 2015 by mythbusters844

[Hcube]

It's just because of the LOX fuel lines that are in the way. As simple as that... Notice the tank is oddly asymetrical: No wonder they need to have asymetrical configurations !

Besides, having a single booster is and looks awesome

[Choctofliatrio2.0]

I was pretty confused when I first saw it, but it kinda makes sense. Main engines and boosters can gimbal very precisely (much more precisely than in KSP, which is why ships with lots of Vectors get wobbly), so it's not too hard to stay stable. Too much power from boosters can shake the payload apart or change the launch profile. 

[insert_name]

According to Tory Bruno, CEO of ULA on Das Valdez's stream, it's to avoid the feed lines, PS I love that autocorrect has ULA in it