The lazy Shuttle Challenge (kinda...) [WIP] [updated 15. march 2021]

[4x4cheesecake]

I'm by far not done yet, still working on the prototype of the shuttle. I'll update this thread every time I've made some progress

After taking a break from KSP, I somehow got drawn back into it a few weeks ago. I installed the typical 100 mods, played around in a new career game but already felt a bit bored after quite some time by the need to grind money for all the missions I want to do. Naturally, I switched to a sandbox game, played around a bit and also began to build a space shuttle once more, just because it can be complicated, beautiful, overengineered and fun at the same time

But why building a shuttle just for the sake of building a shuttle when there is still the shuttle challenge around? I've participated in many missions of the 5th iteration of the challenge before, so why not give it another shot in the 6th iteration. Well, the thing about the shuttle challenge is....you have to do every mission one after the other. Launch, do stuff, land, repeat. While the launch and landing can be tricky in the beginning, it becomes fairly repetitive once you've figured out a good shuttle design and you literally start browsing the internet during the launch. 

With this in mind, I thought myself: Nah, I'm not going to do that again, I feel a bit lazy...I'm going to launch once, perform every kerbin centric mission and then land again. Basically, doing all the fun stuff but less of the boring stuff I'll also aim for the "commander" difficulty, just because  

These missions have the following goals:

STS-1a: Get to orbit
STS-1b: Deploy a 40t pre-build fuelpod in space (circular orbit, must fulfill some tight tolerances for AP and Pe)
STS-2a: Deploy 3+ CommSats in equidistant, geostationary orbit, shuttle has to be in a 350km+ orbit
STS-2b: Recover the previously deployed 40t fuel pod
STS-3: Deploy and assemble a space telescope in a circular, inclined orbit. Have to use 2 MMUs
STS-4/4R: "park" a shuttle with 6 crew members in a circular, inclined orbit, rescue them with another shuttle
STS-5-8: Deploy and assemble a space station, containing 4 specific modules
STS-9: Capture an astroid and land it on kerbin

 

Well, I have to bend some rules to perform these mission, especially 1b, 2b and 4/4R. For STS-1b and STS-2b, I don't allow myself to perform these in direct succession, otherwise, I could just un-dock and re-dock the fuel pod within the same 2 seconds, claiming to have performed these missions, but that's not the point of them.
For STS-4 and STS-4R, I will need a second shuttle but since I want to perform everything in a single launch, I allow myself to carry a second shuttle as part of my payload. At this point, I haven't decided yet if it will be a proper shuttle or just a funny little miniature version which roughly resembles a shuttle. We'll see...

Most missions will be performed in or close to the highest required orbit, so somewhere around 1222km (that's roughly the required Pe for a dive orbit to deploy the geostationary CommSats for STS-2a). This will cover all the other orbital height requirements of the other missions.

At this point, some of you may ask: how the heck will he transport all the different payloads in one go? Well, I guess it's time to present my current prototype for a shuttle which has the capabilities to perform all these missions at once. I proudly present:

The Dragon:

Currently it contains:

-292 parts
-6 MK3 Cargo Bay CRG-100
-7 Vector engines
-21 "Nerv" engines
-101,456 units of liquid fuel (no oxidizer)

It's 53.9m wide and 81.4m long, at a mass of 783.637t.

The first picture was taking during the very first test flight, just to figure out if that beast is ever going to fly at all. As it turns out: it does

Current to-do list:

-fine tune the wing shape
-struts, I need more struts! It's a bit flappy right now
-find a way to include flaps without disturbing the design
-Add RCS

 

Update:

I've worked off the to-do list and here are the results:

The wings became a tiny bit thinner in the middle, were slightly shifted into the back and basically rebuild to align all the parts perfectly:

 

For the flaps, my first attempt was to include a hinge into the tip of the rear wings, which surprisingly works very well to control the pitch but after a few test flight, it had to admit that it is complicated to control (I've used an axial action group to pitch up).
I'll keep the construction anyway, just in case.

Spoiler

In the end, I've decided to "sprinkle" some advanced canards across the whole orbiter. This works well for the design I'm looking for and allows me to control the orbiter in a decent way. For yaw control and stability, I've added some spiky wings to the tail which also include some FAT aeroplane control surfaces.
Yaw stability was one of my biggest concerns so far since large wing areas can easily cause some flat-spin during atmospheric flight. So far, the tail does a great job preventing this  
At this point, the orbiter flights reasonable well, giving the size of the craft. Unfortunately, roll-control is mediocre at best, which makes it really difficult to fly precise maneuvers. I haven't decided yet if I want to attempt to change this or just try to aim more precisely when setting up the reentry.

I've also placed quite a few RCS thruster across the orbiter but I may have to reduce them a bit to find a balance between control and fuel usage. Right now, the 300 units of monoprop are used up within ~75 seconds of continuous firing the RCS thruster. I'll definitely add more monorpop as well but still...

In the meantime, I've also performed some successful test flights, including reentry and landing the orbiter. As it turns out, reentry is a bit tricky but not for the reason I've expected: I assumed the wings will be ripped apart very quick so I had to go for a shallow AOA during reentry. As it turns out, I actually have to use the shallow angle for a different reason: the front of the empty Orbiter is too light to counteract the lift created by the wings so it tends to flip over very quick. an AOA of 10° is already enough to flip the orbiter, so I need to point pretty much straight prograde during reentry. That's unusual and slightly scary but surprisingly doesn't come along with heat issues. 

 

To-Do list:

-find balance for RCS fuel usage
-more test flights to get used to the orbiter
-if necessary, fix issues found during test flights
-start building the payloads

I'll update this post once the current to-do list is worked off

Edited March 15, 2021 by 4x4cheesecake