Staging really needed? Or is my KSP broken?

[tomberry]

Hi all.

I played around with my excel sheets for dv, fuel fraction and so on to get an idea when to do the perfect staging and suddenly I realised that with a fuel fraction(m0/m1) of ~3 you can reach LKO with your first stage.

That means that a Mammoth powered first stage, supported by by some cheap Hammer solid boosters for better TWR on the pad, can lift over 50t into LKO without a second stage. (20t for Mainsail) 

The funny thing is: You can strap 3 or 5 of these stages together and have a payload capacity of 150t oder 250t.

When you manage to survive the reentry and land these monster, you get an incredibly cheap and easy way to bring stuff up. The Mammoth engine has a very high impact tolerance (20m/s), so you can easily land on them with parachutes and a little burst on the last meters. 

 

I use no Mechjeb or other autopilots, so there is still room for improvement. 

My first stage looks like this:

 

Payload

S3-3600 Tank

S3-7200 Tank

S3-14400 Tank

S3-14400 Tank

Mammoth + 4-8 Hammer Solid Boosters

 

I know that the dv requirments in KSP are lower than in reality, but isn´t that to easy? Or is my KSP broken in some kind? 

 

 

[UmbralRaptor]

No, that's correct. ΔV to LKO is less than the effective exhaust velocities of some engines.

[Cavscout74]

3 hours ago, tomberry said:

I know that the dv requirments in KSP are lower than in reality, but isn´t that to easy?

dV requirements for stock scale KSP are a small fraction of reality.  I don't have figures handy, but IIRC its somewhere north of 9000 m/s for Earth.  That's why SSTO spaceplanes are so (relatively) easy in KSP while we're still waiting on one in the real world. 

My first reusable rocket was Mammoth powered & recovered with chutes, and a touch of thrust just before landing.  I had some large mod landing gear rather than landing on the engine, but otherwise the same setup as you.  Worked great till I got tired of landing every first stage.  Especially after a busy interplanetary transfer, I might have 8-10 Nexus first stages in LKO that all had to be landed.

[Superfluous J]

4 hours ago, tomberry said:

isn´t that to easy?

Many of us think so, and we mod the game to have larger planets. I personally prefer 2-5 times larger Kerbin, like you'll find in JNSQ.

[KerikBalm]

That's why I play at a 3x size rescale

[Zeiss Ikon]

Yep, making VTO SSTO rockets in KSP is almost trivial.  There was a challenge thread on this (over in the Challenges board) a couple years ago; I've got a fairly trivial entry there.

These days, I mostly play in Realism Overhaul -- which includes Real Solar System.  Orbital velocity around Earth is about 7800 m/s, the atmosphere is 140 km high (though that last 40 km is pretty danged thin, it will eventually bring down a vessel), and we're playing with real engine performance, mass, fuel choices, and (un)reliability.  Making an SSTO on Earth is just about possible, but making one that can carry useful payload requires the most current engines you can get, and choosing the correct fuel/oxidizer combination (Isp trades off against density, which affects tanks size/mass, storability -- yes, cryogenics boil off -- and toxicity, in the form of increased costs to roll out a completed launcher to the pad).

Short version: there are good reasons almost all modern rockets use kerolox, with a few going for Mixed Oxides of Nitrogen (MON) and a hydrazine derivative, and methylox being the popular new kid.  Yes, hydroloxhas much higher engine performance, but a Space Shuttle burning kerolox could have had an external tank barely bigger than the orbiter, and one burning methylox could probably have had a similar launch profile and payload, still with a much smaller ET.  Want to make a Delta Clipper, X-33, or Skylon in RO, you'll have your work cut out for you (as witness that NASA, ESA, and all those private companies are still flying simulators and making CGI videos).

Meanwhile, the workhorses in the real world are all two stages to LEO.  As noted above, your dV on the pad needs to be 8900-9100 m/s (depending on TWR), and you need a highly efficient launch profile.  I let MechJeb do the flying from ground to orbit, generally...

[RizzoTheRat]

Not tried the Mammoth but my standard KSP lifter is 6 or 7 Vector engines, lifts around 40 tonnes to LKO, and lands back on the runway using KOS (from an equatorial orbit, I haven't quite nailed the landing script for an inclined orbit for Minmus missions).  Multiple Vectors on an engine plate seem to cope with re-rentry heat way better than single bigger engines.

Very tempted to give RSS/RO a try for my next career though as I agree launching is a bit too easy.

[tomberry]

Ok, thank you for your answers. 

Maybe in my next career I should try the Realism overhaul. 

 

[MaxxQ]

22 hours ago, 5thHorseman said:

Many of us think so, and we mod the game to have larger planets. I personally prefer 2-5 times larger Kerbin, like you'll find in JNSQ.

Yes, JNSQ is perfect for this sort of thing.  It scales up the stock system to 2.7x, adds a few new planets and moons, and all can be reached by building a ship from only stock parts, although it WILL be a bit more difficult.

[Bill Phil]

Don't even get me started on the 412s isp engine from Making History... as a core engine you can get some serious payload up there, just don't throttle it up too high until you're at a decent altitude and strap on some solids to get you there. Crazy.

[RealKerbal3x]

3 hours ago, Bill Phil said:

Don't even get me started on the 412s isp engine from Making History... as a core engine you can get some serious payload up there, just don't throttle it up too high until you're at a decent altitude and strap on some solids to get you there. Crazy.

IIRC, the Wolfhound (and Skiff) were nerfed in version 1.6. They’re not nearly so OP now.

[Pecan]

Kerbal Space Program has changed over the years to make SSTOs easier and easier.  The simplest is just 3 parts and can launch a considerable amount.