[Stock] [1.0.5] Honest Jeb - low cost 45 tons to LKO

[Temstar]

Having designed a low cost per ton launch vehicle for the Light Lift category and another one for Ultra Heavy Lift, it's now time to fill the big gap in the middle. Being in the middle can be a bit tricky though - they're too big for monolithic SSTO flyback booster and too small for highly optimised asparagus giants. Some new thinking is needed here.

Of course to make the upper stage reusable is easy - Nova II already demonstrated this feasibility with its Reusable High Energy Upper Stage. The problem is the larger lower stage - they get left behind in the atmosphere and their tend to cost a bomb due to their sheer size. Getting rid of them by making a single stage to orbit rocket also becomes increasingly difficult once your payload get bigger.

Now SRBs are cheap, and if you look at the list of launchers in real life that use them: space shuttle, Ariane 5, Atlas V, Delta IV, etc etc I'm by no means the first person to think of them as a way to reduce the 1st stage price. But if you have played with SRB first stages in early career you would know that they are quite fiddly beasts - you either get too low TWR on lift off, or too high TWR on stage burn out or rocket losing control as SRBs have no gimbling and fins lose control authority.

Then it occurred to me: why not just use MOAR BOOSTERS on a bigger rocket? Having a big payload on top means TWR swing won't be too crazy and the all solid stage will burn out while still in lower atmosphere, where fins still work.

Thus I present you: Honest Jeb Medium Lift Launch Vehicle

Craft file: http://kerbalx.com/Temstar/Honest-Jeb-MLLV
(Craft file contains proofing payload)

Specifications:

•     dry weight: 59 tons
•     wet weight: 268 tons
•     cost: √88,646
•     part count: 99
•     payload: 45.5 tons to 75km x 75km orbit
•     payload fraction: 14.51%

Cost per ton to LKO:

•     without eRHEUS recovery: √1948
•     95% average eRHEUS recovery rate: √770
•     90% average eRHEUS recovery rate: √832

From this you can tell how cheap the first stage is, considering it contributes 1/3 of the delta-V from the bottom. I must say too, that bottom stage coupled with that upper stage and lofting that payload really makes a nice looking rocket.

Typical mission profile
 

Spoiler

 

Launch is simple, throttle up (well no, actually you don't have to since it's you know...), turn on SAS and light this candle. SRBs being SRBs will still have it's TWR growing by quite a lot during it's burn, so you need to be aggressive with the gravity turn - I like to tilt east 5 degrees as soon as my altimeter reads 200m.


Somewhere around 10-11km the SRBs will burn out. Hit stage and the 2nd stage will hot stage. Is it just me or does TR-38-D and Rhino always become sticky during flight and require hot staging?


And here it is, the extended Reusable High Energy Upper Stage in orbit with payload with high degree of precision. Unlike the smaller RHEUS that Nova II uses to handle much much large payload, the eRHEUS of Honest Jeb is sized with enough torque to comfortably handle its payload without resorting to RCS. Still it's equipped with an RCS system to safely move away from the payload after release.


Payload release. Note that this payload is quite aerodynamic and so does not require a fairing. the eRHEUS does have a 3.75m fairing installed so you can use it without having to rebuild the stage if you have draggy payloads. Of course using a fairing will occur some weight penalties.


Delta-V after payload release. Now with a good flight you could in theory carry a bigger payload, I wouldn't recommend it though as I find having loads of delta-V on deorbit help with reducing the heat load and the steeper reentry increases accuracy on targeting a landing site.


Reentry over Kerbin. With a steep reentry angle like this with a 300m/s deorbit burn you can actually safely deorbit the eRHEUS without deploying the airbrakes, but it's a good idea to deploy them anyway for safety. For extremely shallow reentry you may need to pulse the airbrakes to control heat load.


eRHEUS in flight over KSC. I've retracted the airbrakes as it looks like I'm going to undershot.


Safe landing several km from KSC.


Another landing attempt, to show that eRHEUS can safely land in water. It lands vertically and can safely fall on its side without anything breaking off.

 

Edited January 26, 2016 by Temstar

[CommanderCoye]

+rep

[CitizenAerospace]

That is a very cool looking rocket, very economical too! Love highly optimised designs... +rep to you (when I figure out how to give it )

Edited December 15, 2015 by CitizenAerospace

[Turd]

Looks a lot like a Saturn 1B clone I messed with a long time ago, strapping a bunch of SRBs together does make a really economical and attractive first stage.

[Temstar]

Craft file link now updated to KerbalX, the version in KerbalX has been slightly refined compared to the original version in the OP. It's slightly cheaper, and uses about 10% less part count.

Edited January 26, 2016 by Temstar