Benefit of Solid Rockets over Liquid

[Bunzmaster]

As a new player, I apologize if this has been covered before. I tried searching and couldn't find a specific answer.

Are there benefits to using Solid Rockets?

I know the downside of it them not having any thrust control but what are the upsides?

[andrewas]

They're cheap, which will matter in career mode. Also, IIRC they have higher thrust than similarly sized liquid equivalents so, while you don't get as much impulse, they can be useful if your TWR is marginal at launch.

Still, I never use them.

[Landge]

I only use them if I need to get a bit more liquid fuel into orbit than if I launched without them, SRB's that is.

[karolus10]

They cheap, simple and provide a lot of thrust.

[NeoMorph]

Fuelled boosters in asparagus format get more fuel into orbit than using SRBs I've found though.

[Enigma179]

Personally if I feel insecure about my rocket's ability to get up (like if the kerbal engineer says I've got barely 4500 or so dV in my launch stage because I have absolutely no faith in my ability to get even within 500 dV of an ideal launch) I'll throw in a set of rocket boosters to fire alongside the first stage and drop. For me it's mostly a confidence thing but it gets the job done and I *do* notice the difference.

[brooksy125]

Personally if I feel insecure about my rocket's ability to get up (like if the kerbal engineer says I've got barely 4500 or so dV in my launch stage because I have absolutely no faith in my ability to get even within 500 dV of an ideal launch) I'll throw in a set of rocket boosters to fire alongside the first stage and drop. For me it's mostly a confidence thing but it gets the job done and I *do* notice the difference.

I thought solid boosters made you lose deltaV, at least that's what engineer keeps telling me.

[LeonG17]

They're best used in what their called, as boosters. I use them to give me additional thrust on launch stages for heavy payloads as a result of their better TWR compared to the liquid fuel engines.

[Enigma179]

I thought solid boosters made you lose deltaV, at least that's what engineer keeps telling me.

I believe the engineer doesn't actually take into account solid boosters; for me the delta V stays the same when they're added, the only loss being from the decouplers. I guess it doesn't want to calculate the stuff for boosters so just assumes that the extra mass will be cancelled out by whatever the booster's loaded up with?

[Pipcard]

I thought solid boosters made you lose deltaV, at least that's what engineer keeps telling me.

I believe the engineer doesn't actually take into account solid boosters; for me the delta V stays the same when they're added, the only loss being from the decouplers. I guess it doesn't want to calculate the stuff for boosters so just assumes that the extra mass will be cancelled out by whatever the booster's loaded up with?

Kerbal Engineer can take solid boosters into account if you attach a liquid fuel tank (preferably a small one, like the Oscar- to the solid boosters. Just don't forget to take the fuel tank off before flying.

[magnemoe]

They're best used in what their called, as boosters. I use them to give me additional thrust on launch stages for heavy payloads as a result of their better TWR compared to the liquid fuel engines.

Yes, they are nice then the TWR at launch is low.

[Pbhead]

Fuelled boosters in asparagus format get more fuel into orbit than using SRBs I've found though.

ah, but if you asparagus AND put srbs on...

[N_Molson]

SRMs (Solid Rocket Motors) deliver a lot of thrust in a short amount of time, and have a mediocre specific impulse (Isp). They are also simple to ignite and to store (they make excellent ICBMs), and have a decent performance at sea level.

Liquid engines, especially the ones that use "light" fuels like liquid hydrogen (oxydizer is often but not always LOX or liquid oxygen), deliver less thrust in the same amount of time, but have an higher specific impulse. They tend to be mechanically complex, and their ignition requires a complex infrastructure and pre-launch sequence. By the way, specific impulse is the key of spaceflight, so those inconveniences are bearable. They tend to give their best in vacuum.

[SpaceSphereOfDeath]

They're good for first stages to boost up heavy rockets and contain their own fuel, so less mass

also, SEPRATRONS! the're brilliant for boosting away SRB's or fuel tanks on parrel/asparagus staging!

[SmallChange]

I use them as "no though" extra power on my first stage of a lifter, though rarely will I ever start out with plans to incorporate them into a design. If I find my launch vehicle to be a bit more sluggish than I had hoped for, I'll toss a couple on. Also, from a completely roleplay and aesthetic standpoint, their exhaust plumes look cool. There are a couple other benefits though. The thrust to weight of a solid rocket motor right around the time when it's about to burn out is crazy. Also, they have a lower profile than a liquid tank + most engines. Granted, those benefits are pretty small in comparison to the drawback of having no throttle.

[sporkafife]

Strapping on some liquid fuel boosters that feed their fuel into the central stage that are jettisoned when they are empty (asparagus staging) is MUCH more efficient than strapping solid rocket boosters onto your rocket. Look at the "cost" on the part descriptions though. A liquid fuel tank and engine is many times more expensive than the SRBs in the game, which I'm pretty sure is also true for real life. This means that in career mode, SRBs will become much more useful for if you're low on the pennies

[rhoark]

If you put together something that has good dV but too little surface TWR, SRBs are a quick fix.

[Klajan]

SRB are useful, if liquid fuel boosters the same size have not enough thrust or fuel to make a difference. OR you just use them for the lulz.

[Rastaman]

I'm currently experimenting with mostly linear rockets where the whole first stage consists of 20 solids. Like 160 tons of them. It works pretty well. Don't forget winglets for control though.

[Pipcard]

I'm currently experimenting with mostly linear rockets where the whole first stage consists of 20 solids. Like 160 tons of them. It works pretty well. Don't forget winglets for control though.

Overheating?

[Bunzmaster]

Thanks for all the replies. I'm learning alot.

I've currently using them as a first stage to help get my rocket into orbit. As my mainsails start to overheating I can throttle them back, and as I start to reach around 200 m/s I can really throttle back the mainsails and save fuel while the SRB's keep me accelerating/climbing.

Maybe I should try Asparagus staging with Liquid boosters if this setup doesn't hold up too well.

Edited June 9, 2013 by Bunzmaster

[koshelenkovv]

Since 0.20 Engineer do not account any solid boosters correctly.

Also, it calculate beginning from the root part, not from top or part you intended being last. So its calculations may be totally wrong with really sophisticated designs, where staging occurs both on top, bottom and sideways or when vessel blocks get recombined in new vessel configuration, or when you start engines in really weird sequence.

[stupid_chris]

I've currently using them as a first stage to help get my rocket into orbit. As my mainsails start to overheating I can throttle them back, and as I start to reach around 200 m/s I can really throttle back the mainsails and save fuel while the SRB's keep me accelerating/climbing.

Are you sticking the mainsails at the bottom of an orange tank? Those tend to make every engine overheat a lot faster. If you stick the smallest 2.5m tank (X200-16 I think) at the bottom of your orange tank, you have a tiny bit more fuel, not much more weight and it completely removes the overheating bug of the orange tanks. You could throttle up a mainsail to full throttle and let it burn till fuel out and it STILL wouldn't overheat. It's very useful in situations like yours, where you need to throttle down but that throws your TWR off.

The classical stock asparagus design is two orange tanks with one small X200-16 the bottom and a mainsail as the core stage and three pairs of identical boosters on the side. You should get over 70t in orbit with that easily.

[rodion_herrera]

Unless it's really a part of the design, don't add SRBs to a second or third stage of a rocket if you just want "a little boost"--you'll end up in a far higher orbit than you would wish for!

[NeoMorph]

Strapping on some liquid fuel boosters that feed their fuel into the central stage that are jettisoned when they are empty (asparagus staging) is MUCH more efficient than strapping solid rocket boosters onto your rocket. Look at the "cost" on the part descriptions though. A liquid fuel tank and engine is many times more expensive than the SRBs in the game, which I'm pretty sure is also true for real life. This means that in career mode, SRBs will become much more useful for if you're low on the pennies

Easiest way to point out that liquid fueld boosters is that it's like launching the rocket at 10,000 feet or so without the boosters because with the liquids feeding the central tank they fall away at that height and there you have your rocket with a full tank of fuel and your ship is already accelerating away. If you put on SRBs on the other hand, when they fall away your central tank is already 2/3 depleted because it isn't being topped up by they SRBs.

Hence, SRB's aren't as fuel efficient as asparagus liquid fueld boosters. But as people have said... they are cheap.