What is the proper way to use solid boosters?

[Parallax]

I never use them: you cant turn them off and you can't refuel them. I also don't see any reason to use them on a lifter stage over asparagus staged orange tanks + mainsail. Cant really think of any reason to use them any where instead of standard rockets.

am I missing something here?

Edited March 15, 2014 by Parallax

[xoknight]

They are good in low altitude "boost" stage. They pretty much give you a push into space.

[Woopert]

I almost never use them. There is of course the crowd of "moar boosters" (not trying to criticize), but if you're going to add boosters liquid is the way to go.

[Comrade Jenkens]

I like them but they would be a lot more useful if they had longer burn times.

[Woopert]

I like them but they would be a lot more useful if they had longer burn times.

Segmented boosters would be really nice, too. But, I'm sure it's been suggested many a times before.

With them we could do 4 segment boosters like the Space Shuttle, or try advancing the technology and make 5 segment boosters, like on the SLS. I guess a feature could be made to limit the amount of segments used in career and higher nodes in the tree will allow more segments to be stacked. Just something I thought aboout now.

[Hodo]

I used a SRB for my Real Solar System Ares I-X knock off I made. The whole first stage is a long SRB from Stretchy tanks mod. Burns for 150seconds.

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Edited March 16, 2014 by Hodo

[Silverchain]

They're simple and they have a good TWR, so they provide an easy kick for launching.

[cantab]

Explosive decoupling.

Besides that, they're reasonably competitive with non-asparagused liquid boosters. The lower empty mass partly makes up for the lower Isp. Both solid boosters give higher thrust than any 1.25m liquid engine, making them effective first stages on smaller rockets - just stick a decoupler and a booster below each main engine for some easy extra dV.

They're also one part doing what would otherwise need several, which may be a consideration for large rockets.

Really, asparagusing beats just about anything else, since we have simple-to-use massless fuel lines. But if you're opting not to use it, then solid boosters can be useful.

[MarvinKitFox]

Best use of a SRB: providing that first 120m/s kick while launching, when your liquid rockets are still struggling against their own mass and you take too long to speed up.

SRB has a *very* favourable thrust per part count, and quite good TWR compared to any liquid fuel boosters with big tanks.

Tune your fuel rockets to keep you at terminal velocity, and use SRB to kick you to that speed as quickly as possible. Saves quite a lot of delta-v that you would have been wasting puttering around at 50m/s the first minute.

Just dont try to go far, the ISP of SRBs is.... pathetic. About as bad as RCS, really.

[SRV Ron]

SRBs used in this early Career ship gave the boost needed for Jeb to orbit Mum and return.

[maccollo]

1: They are useful sometimes when your launch stage has just barely enough delta V, and you just want to throw on something quick and easy.

2: Your rocket is 50% more awesomer with SRBs.

[Red Iron Crown]

The only SRB I ever use is the Sepatron, to kick expended stages away. Any other use is better served with liquid fueled rockets.

That may change when economics come into play if SRBs are cheap.

[Anton P. Nym]

I use SRBs to help big craft off the pad; they let me use more fuel-efficient but lower-thrust engines for the first 5km or so until they've burnt off enough fuel & oxidiser. They're much simpler to implement and debug than a full asparagus arrangement, and the biggest constraint on SRBs (no throttling) was mitigated when Tweekable thrust limiters were implemented.

You don't have to use 'em, but they're far from useless.

-- Steve

[Cerberus738]

My Hercules lift vehicle (70 ton payload to 100km orbit) uses 40 Solid boosters as the first stage. I use them just to lift off the pad and get up out of the thicker part of the atmosphere. It feels like i'm wasting less fuel that way. they are meant to be expendable anyways so i don't feel bad. except when i forget to start my turn early and they bomb KSC.... ha ha ha whoops.

[Pecan]

Making popcore - Stayputnik or okto cores have a lower heat-tolerance than any other part. One of those on an SRB explodes at ~6km. Pointless, but fun.

[Cerberus738]

Ok just for fun i played with some numbers and flew some test flights....

Using the BACC srb as the starting point....

It has a mass of 7.875t and thrust rating of 315. 850 units of fuel. (not using the isp because i don't understand it completely) i calculate a burn time of 45.7s

To get a comparable burn time with the mainsail you would need 2243 units of fuel (i'm only using liquid for calculations... just assume oxidizer is included With 12 FL-T400 and 2 FL-T100 i can have 2250 units of fuel and calculated burn time of 45.8s

mass.....34.125t

On to the launch test. (going straight up. gimbals locked. full throttle)

First the SRB.. after adding a reaction wheel and probe core final launch mass 8.22t. after launch the srb burned for 48s final AP of 63km. Thrust to mass of 38.3

Mainsail... launch mass of 34.47t. burned for 50s. final AP of 253km. Thrust to mass of 43.5

I would say smaller rockets are better off using SRB to launch with no? Larger lifting rockets could absorb the weight needed to fuel a mainsail....

[Claw]

Ok just for fun i played with some numbers and flew some test flights....

Using the BACC srb as the starting point....

It has a mass of 7.875t and thrust rating of 315. 850 units of fuel. (not using the isp because i don't understand it completely) i calculate a burn time of 45.7s

To get a comparable burn time with the mainsail you would need 2243 units of fuel (i'm only using liquid for calculations... just assume oxidizer is included With 12 FL-T400 and 2 FL-T100 i can have 2250 units of fuel and calculated burn time of 45.8s

mass.....34.125t

On to the launch test. (going straight up. gimbals locked. full throttle)

First the SRB.. after adding a reaction wheel and probe core final launch mass 8.22t. after launch the srb burned for 48s final AP of 63km. Thrust to mass of 38.3

Mainsail... launch mass of 34.47t. burned for 50s. final AP of 253km. Thrust to mass of 43.5

I would say smaller rockets are better off using SRB to launch with no? Larger lifting rockets could absorb the weight needed to fuel a mainsail....

I just checked what you said with a minimal payload. MJ shows the liquid setup has about 775 m/s dV extra, but like you said, weighs nearly 26 tons more.

If you measure the equivalent weight in SRBs (34t), you end up with slightly more than 4 SRBs. the dV is pretty close to the liquid setup but still lags slightly in the TWR department. Using current in game prices, a bundle of 4 SRBs is less than half the price of the liquid setup.

So I suppose the utility of either depends on what you need/want.

[Camacha]

If you do not like asparagus staging for lack of realism, boosters are the way to go. I imagine that money will also give them an advantage, as they are cheap. The lack of throttle is a non-issue, as the first stage should never be throttled on a even slightly proper rocket.

[Vanamonde]

The hint is in the name. They're boosters. They boost. The faster you get off of the ground, the less dV you lose fighting atmosphere and gravity. But it can be difficult to get a vessel moving from a standing start up to an efficient ascent speed, so, you give it a boost, a quick shove to help get the ascent started. Boosters are a cheap way to give your ship that initial shove. And they will become more useful when economics are added to the game.

[Dispatcher]

As has been touched on, SRBs are supplemental to the main engine(s). They can also be used in conjunction with liquid boosters.

[Jouni]

When you have a rocket that feels nice but can't get its job done, adding a few solid boosters is a quick and easy way to get some more thrust and delta-v. If you like designing launcher stages, there are almost always better alternatives to solid fuel boosters. On the other hand, if you prefer to concentrate on the mission stage, boosters increase your ability to reuse the launcher stages you have already built.

The last time I played career mode, I used rockets like this to go to Mun and Minmus:

That triple stack of FL-T800s and LV-T45s is a good and solid workhorse in early career mode, but it's a bit underpowered for the payloads required to land on Mun.

[Camacha]

Don't forget that your TWR typically increases after launch. If you have a wonderful rocket that just cuts it a little too close in the TWR department, you can get the thing flying with boosters.

There is a reason real world spacecraft use them as first stage too

[SpaceK531]

When money becomes a thing, asparagus is going to be seen as the false prophet, and boosters are going to be seen as the road to the future, considering that you only have 1 part for a booster, versus the 40 or so parts that go into asparagusing, a fourth of which are the motors themselves which are a bit spendy iirc.

[AlamoVampire]

Almost if not ALL my ships have SRBs on them. Easy to use cheap to boot. Easy dv imho. Sometimes they are the inly way for my stuff to even have a chance at orbit lol

[magnemoe]

When money becomes a thing, asparagus is going to be seen as the false prophet, and boosters are going to be seen as the road to the future, considering that you only have 1 part for a booster, versus the 40 or so parts that go into asparagusing, a fourth of which are the motors themselves which are a bit spendy iirc.

A bit grapes and melons, asparagus is 3-7 mainsails, 3 skippers is the smallest I use in one launch before I get mainsails.

It also uses 4 solids, SRB can not replace 2.5 m parts but I agree that 1.25 in asparagus is uneconomic