Moar Boosters!- A request for SRB variety

[LorenLuke]

I've noticed a consistent trend among all the main solid rocket systems (not including the separatron, or the launch escape system) available: they're all the small (Mk.1/1.25m) radial cross section.

The RT-5 Flea and RT-10 Hammer are both understandable, being low tier rockets that were 'found lying by the side of the road'. 

However, the BACC is manufactured by Rockomax, which is known for its super-sized Mk.2/2.5m cross sections among its products. The BACC, while double the fuel storage and slightly more thrust, doesn't appear to fall in line with the same design philosophy as the Skipper or the Mainsail; it's just two Hammers stacked on top of each other.

Even more egregious is the Kerbodyne KD25k, which, although is double the thrust and triple the fuel, still barely gives the Rockomax Skipper a run for its money (650kN vs 670kN, and only about 2/3 the Isp) and again at a 1.25m cross section. This is far from the capabilities (or size) of Kerbodyne's Twin Boar, Rhino, Mammoth liquid engines. Even one Vector engine outputs more thrust. It makes no sense.

I say keep the SRBs that we have (maybe have others be the manufacturer) but also add at least one 2.5m and one 3.75m cross sectioned SRB for use to lower part count and complexity, and to fit in with their manufacturer's design philosophy.

[insert_name]

also I would like to see upper stage srbs

[cubinator]

I'm not sure what a 3.75 m SRB would accomplish better than a Mammoth engine cluster with Kerbodyne liquid tanks, but it sure would be fun to play with! I can see 2.5 m SRBs on Shuttle or SLS clones, but a full-on 3.75 m solid booster is hard to justify for anything but the largest missions like bulky Jool-5 motherships or Eve landers. If there was a 5 m main stage to strap it to, I would totally go for it, but otherwise it just seems overpowered compared to other parts. Maybe I'm just being picky about my radial boosters having smaller diameter than my main stages, but that's just me.

31 minutes ago, insert_name said:

also I would like to see upper stage srbs

This would be pretty cool too. I would use tiny de-orbiting SRBs if they were available, and for extra coolness when decoupling rocket stacks.

[LorenLuke]

41 minutes ago, cubinator said:

I'm not sure what a 3.75 m SRB would accomplish better than a Mammoth engine cluster with Kerbodyne liquid tanks, but it sure would be fun to play with! I can see 2.5 m SRBs on Shuttle or SLS clones, but a full-on 3.75 m solid booster is hard to justify for anything but the largest missions like bulky Jool-5 motherships or Eve landers. If there was a 5 m main stage to strap it to, I would totally go for it, but otherwise it just seems overpowered compared to other parts. Maybe I'm just being picky about my radial boosters having smaller diameter than my main stages, but that's just me.

This would be pretty cool too. I would use tiny de-orbiting SRBs if they were available, and for extra coolness when decoupling rocket stacks.

Perhaps not a 3.75, but most certainly a 2.5. Even still, I wholly agree that a 3.75m booster would be fun to play with.

The main issue that birthed this idea is the fact that we have the proper engines to build a Space Shuttle orbiter (Kerbodyne 'Vector'), and even the giant Kerbodyne fuel tank, but have no SRBs to give proportional amounts of thrust with regards to scan (thrust of SSME vs. SRB ratio-wise, as opposed to real world values).

[cubinator]

1 hour ago, LorenLuke said:

Perhaps not a 3.75, but most certainly a 2.5. Even still, I wholly agree that a 3.75m booster would be fun to play with.

The main issue that birthed this idea is the fact that we have the proper engines to build a Space Shuttle orbiter (Kerbodyne 'Vector'), and even the giant Kerbodyne fuel tank, but have no SRBs to give proportional amounts of thrust with regards to scan (thrust of SSME vs. SRB ratio-wise, as opposed to real world values).

Yes, I totally agree with this. I would definitely make good use of a 2.5 m SRB, but a 3.75 m one would be purely for those 'MOAR BOOSTER' moments that have nothing to do with anything productive, unless I felt like trying a 1-launch Eve mission or something.

Speaking of which, I've never actually done an Eve round trip! I should get around to that sometime. But I need to finish my Mun Elcano first.

[juanml82]

I agree. I got SpaceY mostly for the bigger SRBs (and it also has great radial decouplers), as it saves clustering Kickbacks. 3.75m might be too much (for stock), but I think one 2.5m SRB would be a great addition

[AbacusWizard]

I'd really like to see a Size 2 solid fuel booster. For large launches I usually end up making wobbly and awkward-looking clusters of Size 1 solid fuel boosters and replacing each cluster with a Size 2 would make so much more sense.

[Rath]

A 3.75 would only be useful for mega-ares 1 style launchers but I love that style so yeah.  And a .625m one

[Wjolcz]

I am really curious how a 2.5m booster would look like. Probably very chubby. Tiny sized SRBs would be nice to have.

[Nich]

2.5 and 3.5 booster are a must.

[Kerbart]

The BACC made sense when the Jumbo 64 was the largest tank, but now that we have bigger tanks it would definitely be fun to have 2.5m boosters.

It would be essential that it has an axial attachment point at the exhaust—using a monster like that without the ability to blow things up in a spectacular fashion would only be half the fun.

[tater]

Suggest new SRBs as "RATO" for spaceplanes, and we'll likely see 10 added to 1.1 at the last minute, because "spaceplanes."

[LorenLuke]

Since several people have glommed on to the idea of a 2.5m and .625m (Mk.2 and Mk.0, respectively) booster, how does the community feel about being able to have different max thrust/ISP rated propellants? Generally your liquid rockets are a fuel and oxidiser (Hydrogen-LOx), but fuel-oxidiser composition makes everything for the solid rocket. Having a set that might have more Isp but less thrust for upper stages, etc.

Additionally, what about fuelplugs? Just attach them to the top of an SRB (manually, no decouples) and it will pull automatically.

Thoughts?

[TyrannoFan]

I personally am interested in more sepatron variety. The current ones stick out too much, perhaps we could have direct sepatrons like the ones that come with Ven's Stock Revamp? Also, what about stronger ones? Maybe if we had stronger sepatrons we could make some nice custom escape towers. Some nosecones with sepatrons built in would be cool.

[CaptainTurbomuffin]

Just the title is enough: MOAR BOOSTERS!!

On the other hand, you want more variety in the wrong way. There could definitely be more boosters, especially with gimbal, but more size? Definitely not. Even the kerbodyne one with a long name is too big, I nearly never use it (in career games, not SRB-to-Duna-sandbox-challanges). I'd rather like a 6,25m SRB. Going too big is significantly inefficient. You have to carry the large mass of dried-out fuel tanks needlessly. To counter this, staging was invented. The Kerbodyne stuffs are so big that they hurt this way: It's a lot more efficient to have smaller tanks that you stage. If it would be too much, and even more truts wouldn't help, you've reached the limit, and you need to do separate launches. Also, current SRBs offera wide range of variety, as they are highly customisable. Even the 6,25m booster would just be different in aesthetics.

Edited February 25, 2016 by CaptainTurbomuffin

[Cornholio]

Maybe I'm doing something wrong, but I NEVER use SRBs.  I play career and travel far out of Kerbin SOI.

[KerbonautInTraining]

With size a 3 core SRB's are only useful for boosting liftoff TWR from 1.1ish to 1.4ish. On the real SLS they're gonna boost it from 0.6ish to about 1.8. The main reason they can do this is because a TWR of 0.9 at booster sep is no problem in real life, in KSP it's a death sentence.

[LorenLuke]

24 minutes ago, KerbonautInTraining said:

With size a 3 core SRB's are only useful for boosting liftoff TWR from 1.1ish to 1.4ish. On the real SLS they're gonna boost it from 0.6ish to about 1.8. The main reason they can do this is because a TWR of 0.9 at booster sep is no problem in real life, in KSP it's a death sentence.

 

Potentially, but if you have a 1.4 total TWR with a 90 second burn time, that'll still be 15892.2 m/s at the end of the burn. That sounds hardly like any death sentence I'm aware of.

[KerbonautInTraining]

57 minutes ago, LorenLuke said:

 

Potentially, but if you have a 1.4 total TWR with a 90 second burn time, that'll still be 15892.2 m/s at the end of the burn. That sounds hardly like any death sentence I'm aware of.

I'm saying that a TWR of 0.9 after booster sep is a death sentence in stock KSP due to the insane gravity losses. In real life the boosters will burn for 2 minutes and get the stack to over 2000m/s. In KSP you might be going 600m/s when you drop the boosters.

(Also that number doesn't take gravity losses into account)

Actually, how did you get that number...?

1.4 x 9.8 = 13.72m/s^2 acceleration, not subtracting gravity losses

13.72 x 90 = 1,234.8m/s 

Edited February 25, 2016 by KerbonautInTraining

[Guest]

Why would you ever want diversity in rockets? Small, medium, and large are all you need!

In fact, let's forget the huge gaps between boosters that exist in every other kind of engine!

 

Kerbal Space Program needs more variety, period, instead of single-purpose engines like the Vector. Why do you think modding's such a big thing?

This has my unconditional support.

[CaptainTurbomuffin]

4 hours ago, Cornholio said:

Maybe I'm doing something wrong, but I NEVER use SRBs.  I play career and travel far out of Kerbin SOI.

I concur, you are. They are dirt cheap, altough quite unfriendly, and have a limited use, as SRBs have a pretty bad DeltaV-mass ratio, (terrible efficiency), so they'll ruin your craft's efficiency, unless they are the lowest stage. If they are placed in the lowest stage, their inefficiency is not a problem, and they'll give you some extra DeltaV, but most importantly, thrust, nearly for free! Always use them as the bottom stage/booster stage.

 

[LorenLuke]

1 hour ago, KerbonautInTraining said:

 

Actually, how did you get that number...?

1.4 x 9.8 = 13.72m/s^2 acceleration, not subtracting gravity losses

13.72 x 90 = 1,234.8m/s 

You're absolutely right, that's solved for distance using 1/2at^2, not velocity.

My bad... :X

 

Also, you can just subtract 1 from the scalar to get your values minus gravity (i.e. use 0.4 instead of 1.4).

But that's it, you've increased the bottom surface area by 4 times, and the overall volume by just as much, TWR should be the same at start, but grow much larger than other boosters as the fuel burns away as the weight of the shell is only comparable via a linearly, not at a square, doubling or tripling the TWR, no?

[Laie]

1 hour ago, KerbonautInTraining said:

I'm saying that a TWR of 0.9 after booster sep is a death sentence in stock KSP due to the insane gravity losses. In real life the boosters will burn for 2 minutes and get the stack to over 2000m/s. In KSP you might be going 600m/s when you drop the boosters.

You can get away with it, but it's a steep, slow and inefficient ascent. 1.1 after serparation works well enough, though.

I for one hardly use SRBs because they're too weak. The ones we have can provide a little assistance at best, while I really want SRBs to at least double if not triple my thrust at takeoff. I often find myself using the Size2LFB in the role of SRBs.

[Waxing_Kibbous]

Count me in for a 2.5m SRB, and probably a bigger decoupler to handle it.

[Cornholio]

1 hour ago, CaptainTurbomuffin said:

I concur, you are. They are dirt cheap, altough quite unfriendly, and have a limited use, as SRBs have a pretty bad DeltaV-mass ratio, (terrible efficiency), so they'll ruin your craft's efficiency, unless they are the lowest stage. If they are placed in the lowest stage, their inefficiency is not a problem, and they'll give you some extra DeltaV, but most importantly, thrust, nearly for free! Always use them as the bottom stage/booster stage.

 

I know what they're for, but why use them if I don't have TWR issues?  In fact, I typically have the opposite thrust issues, too much where I'm going too fast too quickly.

 

Maybe it's the fact that I use mods such as SpaceY or that I launch everything in modular format so as to cut down on part count during launch.  I do not miss the days of asparaguss-ing two layers of 2.5m tanks and engines together....