Thud LOVE!!!

[Renegrade]

15 hours ago, Aegolius13 said:

The new Spark seems awfully good, and seems to be putting quite a bit of pressure on both the Terrier and Ant.  

Agreed 100%.   Just like the old days.   Mind you, they still do (and did back then) have niches.  Very light and very heavy craft will do better with an Ant or 909 respectively.  The niches are just much smaller than they probably should be :/

15 hours ago, Aegolius13 said:

I was sad we did not get the Pug in stock, but the new Spark is pretty close in terms of a small vacuum engine. But obviously its atmospheric performance destroys the other vac engines.  It's almost a mini aerospike with vectoring at this point.

Maybe they should have nerfed its atmospheric ISP, and had the Twitch be the atmospheric version, like the current Ant vs. Spider situation.

I really wish the Porkjet rocket engines had made it into stock (with something to fix the 'identically named' issue.  Either give 'em a suffix, or combine both models into one with a tweakable to select between boattail and naked versions.  Oh and while I'm on a wish trip, make the mounting rings of the naked ones smaller for better clustering, hehe).  I had quite a bit of fun with the Valiant and Pug.  Plus the upgrading system was neat and would be a good solution for the needs-of-career-progression vs. needs-of-sandbox issues.

I was fairly satisfied with the Spark at 300 vac isp; not sure why it was increased so much.  Personally, I'd prefer if they increased the number of engines rather than trying to juggle the existing ones into roles.  We could have a lifting-Spark-like (Gleam? Glow? Glimmer? Flare? Scintilla?) and a vacuum-Spark then.  Probably a pipe dream, at this point :/

[Racescort666]

I find that I use the Thud in some niche roles. Example: I need more thrust than a Swivel can provide but I also need thrust vectoring: Reliant and 2 Thuds do the trick nicely without having to bump up to a Skipper. Either that or the design doesn't allow for enough space for a Skipper but I need thrust vectoring. I guess the biggest benefit is bolt on thrust vectoring because sometimes you need just a little bit extra control.

Regarding the Spark, I think it's an awesome engine and sometimes have a tough time justifying an Ant when building a tiny sized probe. It's like your options are absurdly overpowered but requires a big booster or miserably underpowered but the optimal payload mass. It would be nice if there was something between them that had maybe 8 kN of thrust and was in the 0.05 t ballpark.

[XB-70A]

On October 24, 2016 at 1:08 PM, Starhawk said:

The Thud was massively nerfed in isp in 1.1

Every times I read this term I remember that :

[Magzimum]

Thuds are used when "Moar Boosters" is actually just a need for "Moar Power", and not "Moar Fuel". So without having to redesign anything, you can slap extra power onto rocket - because there is almost always some empty space radially to my rockets.

[Aegolius13]

5 hours ago, Racescort666 said:

It would be nice if there was something between them that had maybe 8 kN of thrust and was in the 0.05 t ballpark.

That's kind of what you'd get with four Spiders, but you take a sizeable hit to ISP for the privilege.  I think I'd just go Spark and turn down the thrust limiter if needed.

[kurja]

11 hours ago, Aegolius13 said:

That's kind of what you'd get with four Spiders, but you take a sizeable hit to ISP for the privilege.  I think I'd just go Spark and turn down the thrust limiter if needed.

Another gap that I often come across is that there's really nothing in between a 909 and the 200kN engines (30, 45 etc). 

[KerikBalm]

20 hours ago, Racescort666 said:

I find that I use the Thud in some niche roles.

That's really all it is used for... and even then it competes with surface attachabled "inline" engines.

I use it on some cargo VTOLs... like my Mk3 mun cargo VTOL

Spoiler

The vtol with the surface base modules it delivered to the surface:

The VTOL being loaded with modules in orbit:

But in the Mun case, I mostly just land on the main poodle engines as if its a tailsitter, and land on those two prongs, and just use the thuds (which are bound to action groups) to let the front come down gently - since I do want it to be landed horizontally for rovers to roll on and off. For takeoff, they fire only very breifly as well. As I use them only veyr briefly, I'd want TWR out of them the most, but their TWR is unimpressive.

I also use them on a similar Duna craft:

Spoiler

Here's an older version with different main propulsion engines... 2 aerospikes was not enough hence the "upgrade" to 2 skippers and 2x LVNs

But in that case... the Aerospike has superior TWR, and Isp... so the aerospikes are preferable... The thud thrust vectoring is the only advantage... but in a low profile like this, that doesn't yield much pitch authority (RCS an vernors are needed for that, or action grouped engines near the nose)... mainly just yaw authority which wasn't needed so much. mainly I actually put them there for looks... the aerospikes have a low enough profile (in that 2nd image, the rear main gear have been retracted to make the ramp angle shallower, they have much more clearance on initial landing.

I almost went without them completely, and used a pair of vectors mounted on the wings ( a single oneunder the main body had too little clearance... but I could have tried a bit of part clipping)... but ultimately their niche was "looks", because I do like the look of them.

My number one desire for them is that they have a high TWR, for cases where you want a lot of thrust, but not for a lot of dV (retrorockets for soft landings)

[Racescort666]

16 hours ago, Aegolius13 said:

That's kind of what you'd get with four Spiders, but you take a sizeable hit to ISP for the privilege.  I think I'd just go Spark and turn down the thrust limiter if needed.

I threw together a spreadsheet to see what the hypothetical difference would be. The dV hit for the lower ISP isn't too bad. For 2 craft of the same mass (same fuel fraction as well) it's about 8.6% (the ISP percentage increase). I was looking at a payload mass (since this is an upper stage) of 0.745 t and you get 2190 m/s with 4 spiders and 2379 m/s with a new hypothetical engine that's identical except improved ISP. 

I'm sure that there are other people who run much smaller dV margins than I do that could use that extra 189 m/s, maybe it would be nice for additional maneuvering once in orbit, I don't know. The way I envision this probe is as the return portion of an Eve lander and I'm not going to know if the 189 m/s is going to make the difference until I'm flying the mission. Maybe I play sloppy but I generally leave a wide margin for that kind of thing.

[KerikBalm]

8 hours ago, kurja said:

Another gap that I often come across is that there's really nothing in between a 909 and the 200kN engines (30, 45 etc). 

well, you've got the lv-n at 60 kn... but due to its TWr being so far outside the range of the other engines, I can see why you don't include it.

But you seem to forget about the wonderful aerospike, coming in at 180 kN.

It is only 1.0 tons, compared to the Thud's 0.9 tons...yet it has 50% more thrust (180 vs 120). Excluding the vector, the Aerospike has the best TWR of the 1.25m and smaller LFO engines.

Yet the Aerospike still feels weak as a lifter engine... I'd like to see its mass increased, and its thrust proportionately increased to over 200 kN.

Meanwhile, I wouldn't mind if the thud's mass were decreased to 0.6 tons, giving it a vacuum TWR of about 20.

Its simply too heavy now to really be competitive with aerospikes, but I can see a niche use where it combines with aerospikes on liftoff for gimbal control and extra thrust (because while the spike has a good TWR, its absolute thrust is rather low), and then they get shutdown at higher altitudes. The mass needs to come down for that to work though... Hauling 1.8 tons of deadweight (for a thud pair) is... not good

[kurja]

5 hours ago, KerikBalm said:

well, you've got the lv-n at 60 kn... but due to its TWr being so far outside the range of the other engines, I can see why you don't include it.

But you seem to forget about the wonderful aerospike, coming in at 180 kN.

It is only 1.0 tons, compared to the Thud's 0.9 tons...yet it has 50% more thrust (180 vs 120). Excluding the vector, the Aerospike has the best TWR of the 1.25m and smaller LFO engines.

Yet the Aerospike still feels weak as a lifter engine... I'd like to see its mass increased, and its thrust proportionately increased to over 200 kN.

Meanwhile, I wouldn't mind if the thud's mass were decreased to 0.6 tons, giving it a vacuum TWR of about 20.

Its simply too heavy now to really be competitive with aerospikes, but I can see a niche use where it combines with aerospikes on liftoff for gimbal control and extra thrust (because while the spike has a good TWR, its absolute thrust is rather low), and then they get shutdown at higher altitudes. The mass needs to come down for that to work though... Hauling 1.8 tons of deadweight (for a thud pair) is... not good

But the lv-n and 909 have the same thrust, 60kN?

I did forget about the aerospike! Altough at 180kN it's pretty close to the ~200kN engines and having no attachment node on the bottom it's use is a bit limited. I'd really like an in-line vac engine or two around 120-160kN.

[KerikBalm]

ah yea, I forgot, they buffed the 909 to 60, it used to be 50

But you've forgotten a change they made as well, the aerospike does have an attachment node on the bottom now

[panzer1b]

I will say that the thud isnt exactly useless, but it isnt very competitive against the rest of the engines.  Right now, (at least in my gameplay) i use the thud for heavy VTOL craft, supplementary boosters for smaller rockets (usually when i want a bit more kick but dont want to make the rocket more draggy or switch to a stronger engine, heavy duty missiles (the thud is one of the best engines on those as it has both great thrust, gimbal (you;d be surprised how big a deal gimbals are on ship-ship missiles), and weighs enough to make a decent impactor), and finally aesthetic designs where i want radially strapped on engines in the thud size (quite a few dropships use em as the forward propulsion, they look perfect there).

Other then that, the thud is too heavy and has too low ISP to be of any serious consideration (and highish gimbaling is not a good enough selling point), and it diesnt really have the TWR either (the aerospike puts it to shame in that dept).  While the radial attach is an advantage in many regards, most of the time you will be better off with radial fuel tanks with aerospikes or whatever other engine you want below, yeah its more draggy, but overall the better ISP and extra fuel you can bring in the nacelles counteracts the minor drag penalties.  The only serious spot it gets is as a dedicated VTOL engine since it is perfect for that application, and the terrible ISP isnt a big deal for a rapid burst to land (still wish it weighed like half as much so i didnt have to drag like 1.8-3.6 tons per ship of for all intents and purposes dead weight)...

Edited October 29, 2016 by panzer1b

[kurja]

6 hours ago, KerikBalm said:

ah yea, I forgot, they buffed the 909 to 60, it used to be 50

But you've forgotten a change they made as well, the aerospike does have an attachment node on the bottom now

Woot?! I didn't play the few previous versions and don't have the aerospike in my 1.2 career yet, I did not know this!!

Still, 180 is three times as much as 60.. 

[Nich]

7 hours ago, panzer1b said:

I will say that the thud isnt exactly useless, but it isnt very competitive against the rest of the engines.  Right now, (at least in my gameplay) i use the thud for heavy VTOL craft, supplementary boosters for smaller rockets (usually when i want a bit more kick but dont want to make the rocket more draggy or switch to a stronger engine, heavy duty missiles (the thud is one of the best engines on those as it has both great thrust, gimbal (you;d be surprised how big a deal gimbals are on ship-ship missiles), and weighs enough to make a decent impactor), and finally aesthetic designs where i want radially strapped on engines in the thud size (quite a few dropships use em as the forward propulsion, they look perfect there).

Other then that, the thud is too heavy and has too low ISP to be of any serious consideration (and highish gimbaling is not a good enough selling point), and it diesnt really have the TWR either (the aerospike puts it to shame in that dept).  While the radial attach is an advantage in many regards, most of the time you will be better off with radial fuel tanks with aerospikes or whatever other engine you want below, yeah its more draggy, but overall the better ISP and extra fuel you can bring in the nacelles counteracts the minor drag penalties.  The only serious spot it gets is as a dedicated VTOL engine since it is perfect for that application, and the terrible ISP isnt a big deal for a rapid burst to land (still wish it weighed like half as much so i didnt have to drag like 1.8-3.6 tons per ship of for all intents and purposes dead weight)...

I hate to say it but comparing the thud to an aerospike is like comparing a whiplash to juno for an SSTO

[panzer1b]

9 hours ago, Nich said:

I hate to say it but comparing the thud to an aerospike is like comparing a whiplash to juno for an SSTO

The reason i compared those 2 in terms of TWR is that they both are roughly the same weight (0.9t vs 1t).  That and in space the aerospike is better in every single way compared to the thud with the notable exception of radial mount and gimbal.  Im not saying they are the same engine by any means, but in terms of a pushing engine on rockets, the thud is inferior to the aerospike in almost every way, thats why i used it as an example...

As for whiplash vs jumo, you cant compare those 2 because they arent even roughly similar in any regard (besides being jet engines)...

[Baricus]

I find they work great on sky-cranes, especially for heavier payloads.  Most of the time, though, I use them on spaceplanes for a little extra thrust (I guess that applies to rockets as well).  They also look pretty neat if you clip them in a little so that they mesh with the side of the tank they are attached to.  

[Jacke]

I saw this thread and thought "Thuds in KSP ?!?"  Different Thud.

 

Edited November 3, 2016 by Jacke

[tater]

26 minutes ago, Jacke said:

I saw this thread and thought "Thuds in KSP ?!?"  Different Thud.

 

Was gonna post something similar, myself.

[natsirt721]

The thud is really only useful for surface-to-orbit operations, places where fuel usage is less of a consideration and form factor and control are dominant to efficiency.  For a medium-sized orbit-to-orbit ship there are a plethora of engines which perform better.  Maybe use them to augment control on large ships?

Radial-attach lets you leave the bottom node open, useful for vacuum lander cranes and whatnot.  The large gimbal range lets you land asymmetric payloads with a little more ease.  They can also be used in career to make a proto-shuttle with the Mk2 parts, as they are the only engines available before the KS-25 with enough gimbal range to do a proper shuttle.

I never considered using them on first-stage launch vehicles as SRBs usually provide enough extra thrust for my needs, but I'll see if I like using them.  Someone mentioned they improve control for recyclable first stages, something that I'm currently working on in my career game.

[DrunkenKerbalnaut]

I use them for early career bamboo-staged orbital craft. You do it right, and you can recover most of the craft. Or at least the expensive parts. Of course, you could probably finagle better return on investment with solid boosters. 

[boomchacle]

The Thud is very good for small ICBM's and STSMs as it has a VERY high thrust for its size and also has a very high thrust vectoring angle.

[Spacetraindriver]

On 10/28/2016 at 5:18 AM, KerikBalm said:

I use it on some cargo VTOLs

 

 

[Leafbaron]

works well for early LFO SSTOS on account of the relatively high atm and vac. Isp.

[XB-70A]

Now as I re-discovered this topic it makes me realize that most of my tiny shuttles use the Thud... they are present on nearly all these spacecraft.

[foamyesque]

I actually like 'em as an orbital manouvering system for asymmetric crafts or ones that have CoM shifts, since the huge gimbal range allows them to compensate easily.