more solid rocket boosters in stock?

[Daylight4449]

it would be nice to see some new solid rocket boosters like a 2.5 wide super-booster, or a small booster like those on the Delta-III rocket.

[klgraham1013]

Yep.  Would have been nice. 

[wumpus]

Don't the thumpers resemble the Delta-IV rockets closely enough?  At some point post 1.2 I rechecked the math and noticed that kickers weren't optimal to the point of overshadowing all other SRBs (what I remember easily noticing pre-beta and not changing my rocket designs) and work well enough.

To reduce cost, you might stuff 2-3 thumpers on each side-mounted decoupler, but they should work well enough (aerocaps are a hard choice.  I think you can add a third thumper for the price of two cheap aero caps).

[OrbitalBuzzsaw]

Yeah, it's long overdue.

[Gaarst]

With gimbal and thrust curves as well.

[sevenperforce]

In addition to larger SRBs, I'd like to see some very small vacuum-optimized SRBs to use as kick stages. Like, something the size of the monopropellant engine.

Nozzle deflection setting on SRBs would be great as well.

[wumpus]

14 hours ago, sevenperforce said:

In addition to larger SRBs, I'd like to see some very small vacuum-optimized SRBs to use as kick stages. Like, something the size of the monopropellant engine.

Right now seperatrons appear to work in that function, but only have a vacuum Isp of 154s.  Perhaps if they simply bumped that up it would be enough.

I'd like to see thrust curves on SRBs, but that sounds like an even more difficult UI problem than a thrust coding problem (since you can change thrusts of other rockets in real time, it can't have *too* many assumptions about fixed thrust.  Not sure I'd like to code the UI).

[sevenperforce]

17 minutes ago, wumpus said:

Right now seperatrons appear to work in that function, but only have a vacuum Isp of 154s.  Perhaps if they simply bumped that up it would be enough.

I'd like to see thrust curves on SRBs, but that sounds like an even more difficult UI problem than a thrust coding problem (since you can change thrusts of other rockets in real time, it can't have *too* many assumptions about fixed thrust.  Not sure I'd like to code the UI).

If you go in and change the cfg files you can make the stock SRBs in-flight-restartable with no other adjustments.

The separatrons already have the highest burnout twr of any engine in the game, so amping up their Isp would make them a bit OP. I was thinking of something similar in shape to the Place-Anywhere Linear RCS Thruster, but larger. The Star rocket motors would be a good example; the highest-performing ones can get up to 297 s of Isp, which is really quite impressive. Of course, the Kerbal version would have a much lower propellant fraction and thrust than the real thing, and would be physically smaller. It would be a good choice for circularizing kerbostationary satellites quickly. With the same attach behavior as the Vector (surface or node attachment), it could be used alone or in a cluster.

Since you can adjust the thrust limiter for SRBs already, a thrust curve isn't outside the realm of possibility; it would be like a preprogrammed change. Of course that would be messy and advanced tweakables would get really complicated. Whenever I want a thrust curve for SRBs, I just make a cluster of two or three pairs and set each pair to a different thrust limiter, so thrust starts off high and then drops gradually when each pair burns out in turn.

[CobaltWolf]

1 hour ago, sevenperforce said:

If you go in and change the cfg files you can make the stock SRBs in-flight-restartable with no other adjustments.

The separatrons already have the highest burnout twr of any engine in the game, so amping up their Isp would make them a bit OP. I was thinking of something similar in shape to the Place-Anywhere Linear RCS Thruster, but larger. The Star rocket motors would be a good example; the highest-performing ones can get up to 297 s of Isp, which is really quite impressive. Of course, the Kerbal version would have a much lower propellant fraction and thrust than the real thing, and would be physically smaller. It would be a good choice for circularizing kerbostationary satellites quickly. With the same attach behavior as the Vector (surface or node attachment), it could be used alone or in a cluster.

Since you can adjust the thrust limiter for SRBs already, a thrust curve isn't outside the realm of possibility; it would be like a preprogrammed change. Of course that would be messy and advanced tweakables would get really complicated. Whenever I want a thrust curve for SRBs, I just make a cluster of two or three pairs and set each pair to a different thrust limiter, so thrust starts off high and then drops gradually when each pair burns out in turn.

-ctn-'s Phoenix Boosters are a good example.

@sevenperforce it really is amazing what kinds of ISP they've been able to get out of vacuum solids. The big reason for using them, to my understanding, is just that they're so darn simple and foolproof.

I agree with the general sentiment of the thread, I think there needs to be a 0.625m SRB (with or without a nosecone, depends on when it unlocks I guess. Not having one makes more sense since then it could be a small first stage...), 1.25m and 0.625m vac SRB, and one or two lengths of 2.5m SRB (can model them on the AJ-260 that was prototyped in real life).

[Hotaru]

2 hours ago, wumpus said:

I'd like to see thrust curves on SRBs, but that sounds like an even more difficult UI problem than a thrust coding problem

It's not necessarily as bad as it sounds. One option is to have them built-in: have a toggle between constant thrust and a thrust curve providing constant TWR. Another is to have two thrust limiter sliders, one for the beginning and one for the end, and use a simple linear curve between them. This mod by @Crzyrndm does that second option pretty well.

[NSEP]

20 hours ago, Gaarst said:

With gimbal and thrust curves as well.

Yeah! I'd love to use thrust curves that would be nice.

I support this.

[SupperRobin6394]

Me: "I can't go to orbit, what's wrong?"

Cousin: "MOAR SOLID FUEL BOOSTERS!"

 

Yeah he's been saying that for about 2 years now, nice suggestion, I like it

[wumpus]

21 hours ago, SupperRobin6394 said:

Me: "I can't go to orbit, what's wrong?"
Cousin: "MOAR SOLID FUEL BOOSTERS!"

Yeah he's been saying that for about 2 years now, nice suggestion, I like it

Two years ago rockets didn't get so unstable when the SRBs burned out.  It worked better then.

On 9/1/2017 at 8:09 AM, sevenperforce said:

If you go in and change the cfg files you can make the stock SRBs in-flight-restartable with no other adjustments.

Being able to turn off a SRB is just wrong.  You might be  able to make the thrust near-zero (I think some ICBMs do this.  Jettisoning the nozzle is an obvious means but I think the real method is less dramatic), but it will still consume its fuel at the same rate.  I think there was a thread that tried to find the means of extinguishing a SRB, and it was amazingly difficult (liquid N₂ probably wouldn't do it).

On 9/1/2017 at 10:00 AM, CobaltWolf said:

 

@sevenperforce it really is amazing what kinds of ISP they've been able to get out of vacuum solids. The big reason for using them, to my understanding, is just that they're so darn simple and foolproof.

I'm pretty sure that most of it comes from replacing the heavy steel casing with carbon fiber or similar (composite might be better for the stresses in question).  Technically the Isp doesn't change (since the casing is dry weight) but if you consider the entire thing an engine it still compares well to liquid.

Edited September 2, 2017 by wumpus
undoing a double post

[sevenperforce]

6 hours ago, wumpus said:

Two years ago rockets didn't get so unstable when the SRBs burned out.  It worked better then.

Being able to turn off a SRB is just wrong.  You might be  able to make the thrust near-zero (I think some ICBMs do this.  Jettisoning the nozzle is an obvious means but I think the real method is less dramatic), but it will still consume its fuel at the same rate.  I think there was a thread that tried to find the means of extinguishing a SRB, and it was amazingly difficult (liquid N₂ probably wouldn't do it).

I was just talking about the code's capacity for adjustment.

6 hours ago, wumpus said:

I'm pretty sure that most of it comes from replacing the heavy steel casing with carbon fiber or similar (composite might be better for the stresses in question).  Technically the Isp doesn't change (since the casing is dry weight) but if you consider the entire thing an engine it still compares well to liquid.

No, Isp has definitely increased. A carbon-fiber or COPV chamber can handle significantly higher chamber pressures without damning mass increase, and higher chamber pressure means higher Isp.