2.5m parts some extra's/changes needed

[MaxL_1023]

It is, although I am not sure how much cheaper a SRB would be at that scale in terms of $/payload. A game balance issue if anything. 

[tseitsei89]

Didnt read the entire thread but what we need is IMO:

for 2.5m parts:

1. LF tanks to use with nukes!!! I really cant stress this enough... We just really really need them.

2. Bigger SRBs

3. Maybe a bigger rapier/jet engine but I'm fine with using quadcoupler and 4x rapiers

4. Bigger nuke maybe?

 

for 3.75m parts:

1, Bigger landing legs. It is irritating to spam loads of of them...

2. Bigger chutes. Same as above

3. Bigger nuke maybe?

[Carl]

Quote

A 2.5m SRB might fit in stock, but it would be wasteful in terms of mass and efficiency compared to liquid fueled boosters. 

 Like this

Actually they're very mass efficient, thats because an empty SRB weighs a lot less than an engine plus empty tanks.

 

Also very cost efficient.

 

Also lower drag.

Edited January 7, 2017 by Carl

[Carl]

For reference 2 bare bones solo boosters. each had a 0.04t probe core, 1 MJ, one big square battery, and 4 fins. Each also got a size appropriate nosecone. the liquid had the fuel carried droped to bring it's burn time in line with the SRB, (actually it's a second less but w/e). Note the difference in apotheosis and burnout velocity. Thats despite the fact that the liquid has the better TWR on the pad. Most of thats drag, but some is the much better burnout TWR in the upper atmosphere.

 

 

[Speeding Mullet]

7 hours ago, Carl said:

I mean it's still a cool redesign, but it msises probably the biggest core part of the design of the original, namely the side on landing.

I get the point and don't worry absolutely not taking it the wrong way, it's a good robust exchange of ideas and help that I love so much about this forum!

It is definitely designed for an intermediate pilot for sure, but the point was there is efficiency to be made in your design such that the extra parts from the locked tech tree you crave are not required.  Here's another go then.  I gave you the 4 solar panels, and added your third large reaction wheel, landed at 3.3 m/s with 8 chutes and no powered landing, saved9180 and 4.1t, possibly enough mass to make your upper stage a little smaller, or your lift vehicle more efficient etc.

These things (piloting skills, building efficiency etc) all come in time with a game with a learning curve as steep as KSP, so keep playing around and experimenting with alternative solutions to your problems.  Run a concurrent sandbox game to test your designs in a "simulated" environment perhaps, but definitely keep pushing forwards and playing around , and bouncing around ideas here when you need.  I remember my earliest days when just getting to orbit was heroic achievement.  The day I completed my first Jool 5 mission was probably when I realised I was a relatively accomplished player and could start to suggest engineering solutions on the forums here. 

Good luck with your mission!

SM

Edited January 8, 2017 by Speeding Mullet

[Carl]

Glad you didn;t take it the wrong way, some would have. And wow, didn't realise those big chutes could be mounted off a node. DuH! Those look like they'd rip tons of the part count. Yay.

 

To be fair as you can tell i tend to over engineer a fair bit in my designs.

[Speeding Mullet]

1 minute ago, Carl said:

Glad you didn;t take it the wrong way, some would have. And wow, didn't realise those big chutes could be mounted off a node. DuH! Those look like they'd rip tons of the part count. Yay.

 

To be fair as you can tell i tend to over engineer a fair bit in my designs.

Yep, I keep popcorn in the cupboard especially for those threads!  Yeah the big chutes are super powerful.  You could even add 4 more just to be safe and still be well under-weight and have a much reduced part count.  To mount the chutes I simply placed a small cubic octagonal strut down and then added the chute to it, using the adjustment tools to clip it into the hull a little bit for aesthetics.  If you are adding more chutes you might want to mount them on the sides rather than towards the top, just for balancing purposes.

I always over engineer my designs also, going for looks over weight every time.  I don't actually like minimalist designs, I was just trying to prove the efficiency point.  I'd have bits hanging off every which way just for the hell of it.  An example would be this Mun/Minus science craft.  a little over engineered I'm sure you would agree

 

SM

[Carl]

Eh, reminds me of an old design of mine. Posted the testing log, (in the old versions thread) from a comp i was involved in december 3 years back where i tested everyones designs, chose a random location on the moon for the landing site. Was a 45 degree slope. Mine was the only one to get down and not topple .

Edited January 8, 2017 by Carl

[Red Iron Crown]

3 hours ago, Carl said:

For reference 2 bare bones solo boosters. each had a 0.04t probe core, 1 MJ, one big square battery, and 4 fins. Each also got a size appropriate nosecone. the liquid had the fuel carried droped to bring it's burn time in line with the SRB, (actually it's a second less but w/e). Note the difference in apotheosis and burnout velocity. Thats despite the fact that the liquid has the better TWR on the pad. Most of thats drag, but some is the much better burnout TWR in the upper atmosphere.

<snipped pics>

The near total lack of payload rewards low dry mass on the booster itself while minimizing Isp effect, and the extremely high TWR of both accentuates drag differences. You've also used a lighter booster for the LFB, and it had fuel tweaked out to make its mass ratio even worse.

Try making an LFB that is the same mass as the SRB using the Skipper engine (and neck it down to 1.25m at the top so identical payloads can be used), and put a 10t payload on both. You'll see the LFB performs much better.

[MaxL_1023]

Liquid boosters really shine when used at launch to support a heavy core stage - the dry mass of the booster itself is negligible (compared to the wet mass of the core stage, which counts as time-varying dry mass from the viewpoint of a booster) rewarding ISP to a much greater degree. Liquid boosters are also throttleable, assisting with max-Q navigation, often have a wider gimbal range and can be restarted for SpaceX fans.

In RSS/RP-0 I almost never use solid boosters unless I am being lazy with a fixed payload - optimized launchers are almost always liquid based.