How to have a first stage with two SRB and no decouplers?

[martincmartin]

Sometimes, having 3 Thumpers is just too much, I want 2.  But I don't want to use radial decouplers, because they're expensive: 600 each, and Thumpers cost 850!  So, I'd like a stage that's 2 Thumpers, without using radial decouplers.

I've tried using 4 or 5 Modular Girder Segments stacked vertically, and attaching the Thumpers to them, but the girders are really wobbly, and the whole rocket tends to lean to one side or the other, and the inline reaction wheel isn't enough to counter act.  So I can't get a decent gravity turn out of it.

Thoughts?  Think of it as a challenge: Can you build a 2 Thumper first stage for not much more than the cost of the 2 Thumpers?

[blowfish]

You could use the bi-coupler or adapter.

[FancyMouse]

There's a part named small hardpoint which only costs 60

[suicidejunkie]

Mount the Thumpers to the side of a stack decoupler?

Burn off the boosters with the jet wash of the 2nd stage?

[sardia]

24 minutes ago, suicidejunkie said:

Mount the Thumpers to the side of a stack decoupler?

Burn off the boosters with the jet wash of the 2nd stage?

This. Let us know if you need a picture example.

[Snark]

Moving to Gameplay Questions.

[monstah]

Earlier in career, you could use a girder as a central body, and attach both SRBs radially. Not very aerodynamic, VERY Kerbal.

[pincushionman]

Given how cheap SRBs are any clever solution you can find that works is not going to be significantly  less cheap than than the normal way. But here goes:

baseline:

2x thumpers = 2 x 850 = 1700

2x TT-38k = 2 x 600 = 1200

total = 2900

 

proposed solution:

3x thumpers, 2/3 fuel, 2/3 thrust = 3 x 686 = 2058

1x TR-18A = 400

total = 2458

 

You save a whopping 442 funds.

[Plusck]

You could also use 5x Hammers, limiting thrust to about 55-60%, giving a cost of 2000 (plus stack decoupler). Or 1x Thumper + 2x Hammer @ 60% thrust (they should burn out half a second before the Thumper does), giving a cost of 1650 funds and a total of 97% of the thrust of two Hammers..

[wumpus]

Connect a modular girder segment  to your [vertical] decoupler, then connect two more modular girder segments sticking out (so a green blob is facing outwards).  Connect thumper to modular girder segments.   Total extra cost: 75 funds.

Optional: use 5 girders straight down and no sideways girders.  If your thumpers are occluded by a sufficiently wide uppers stage, this might be helpful.  Possible use: use this (or cubic octagonal struts) to "leave out" the center stage on larger rockets and possibly get better aerodynamics.

[Vegetal]

20 hours ago, FancyMouse said:

There's a part named small hardpoint which only costs 60

Everyone with complicated solutions.... Just use these already.

[Noobton]

On 4/2/2016 at 4:46 PM, Vegetal said:

Everyone with complicated solutions.... Just use these already.

The only problem is that the small hardpoint is very deep on the tech tree, on the advanced aerodinamics node.

[Vegetal]

3 minutes ago, Noobton said:

The only problem is that the small hardpoint is very deep on the tech tree, on the advanced aerodinamics node.

Indeed. The op didn't tell us at what level he is on his career, but I can guess it's still an early one. Would need to know what he has access to in order to give the best advice.