Experienced Engineer Needed

[Mr. Peabody]

O.K. guys, this is my latest project:

https://imgur.com/i2DNRsF

Sadly I can't figure out how to boost the DV without destroying the TW ratio and altering the shape of the engine nacelles. Can anyone give me some advice on where I should start in order to get this rocket working?  (I need it to at least reach LKO.)

[FleshJeb]

With the engines under fairings and the resources panel closed, what you're going to need is an experienced psychic.

I did some math, and I'm guessing you have LV-T45 Swivels under there?

You either need a higher ratio of fuel to dry mass, or to add some side boosters.

[dire]

Step 1, add a first stage booster. A trio of Thumpers or a 2.5 meter center stack are going to get you to an elevation where your upper stage can do some good.

You don't have to worry about the thumpers altering your profile because you'll be jettisoning them shortly after launch.

Step 2, if you are still short of orbit, add moar boosters.

Just to be perfectly clear, these thumpers should be below the current rocket and attached via decouplers. You activate them on the launch pad and jettison them when they are out of fuel.

Edited November 3, 2018 by dire
I charge very reasonable hourly rates for my services as a psychic xD

[AeroGav]

Why do people tease us by asking something potentially interesting,  but don't give us complete information and (often) never post back in the thread they created...  or if they do, not for days?

That rocket is stunning,  i presume he is trying to replicate some sci-fi ship ?  I presume it also has to SSTO off some body or another.. Kerbin..    anywhere else?

More delta V,   not allowed to reduce TWR (can't add fuel) , can't use different engines.  Probably not much scope for reducing payload fraction either..  can anyone do the math re: emtpy weight and full weight? 

Options not looking great.

I'm thinking

a)  change the Swivels for Aerospikes,  slightly better ISP SL and VAC,   they are a little pointy but probably not pointy enough for the OP.   Or clip them inside an NCS adapter for same effect

b) Make a Kerbin/Laythe SSTO by swapping that centreline  bottom facing shielded docking port for a RAPIER.     Swap the three outboard engines for Reliants.   Use them to get it off the deck and up to a velocity where the RAPIER is going to go nuts...   it will then boost you to 1300 m/s or so,  finish the job with your chem engines.

I presume the docking port is another "non negotiable" thogh

[swjr-swis]

16 hours ago, The Dunatian said:

O.K. guys, this is my latest project:

https://imgur.com/i2DNRsF

Sadly I can't figure out how to boost the DV without destroying the TW ratio and altering the shape of the engine nacelles. Can anyone give me some advice on where I should start in order to get this rocket working?  (I need it to at least reach LKO.)

With a lot of lacking detail and no craft file shared, all we can do is try to build a lookalike and see if it can work. I built mine in 1.3.1, which makes the fairing and tank textures different, and the pod is an Mk1-2 (no Mk1-3 in 1.3.1). But this should load and work as is in 1.4.x or 1.5.x too. It makes it comfortably to LKO 80-200km. There's still plenty of unused space under the fairings to add more stuff or fuel, and there is a big surplus of TWR, so there is potential to expand it or use it beyond LKO.

I can't tell what you used between the rockomax brand adapter 2 at the top, so I put in a large battery. For the nacelles I switched the intake (heat & drag), and I used a combo of Whiplash and Dart for the engines. Obviously everything under the opaque fairing in your screenshot is a complete guess in mine - I mostly filled it with 1.25m LFO tanks, which still leaves a lot of empty space.

Ascent is easy: the rocket is pre-tilted so all you need to do is stage and switch SAS mode at the right moments and it will steer itself. Instructions are in the craft description.

 

A few screenshots:

Spoiler

I call it "The Dunatian Psychic". Edit 2c. Because I edit. A lot.

Leaving the KSC behind.

Aft view showing the Whiplash+Dart engine combo.

Makes it to 200+ km LKO.

Craft file: https://kerbalx.com/swjr-swis/TheDunatian-Psychic-2c

Full album with record of ascent to LKO 200km: https://imgur.com/a/CQG8cCe

 

[Mr. Peabody]

Sorry guys I didn't mean to post a low-detail request.

To answer some of your questions, yes, the engines used are LV-T45 Swivels. The craft is actually a replica *attempt* of the original Thunderbird 3 SSTO. My main problem is that I am hoping to avoid engine clipping while avoiding any major changes in shape, which will really complicate matters. I will post a resource screenshot next chance I get.

Edited November 3, 2018 by The Dunatian

[swjr-swis]

19 minutes ago, The Dunatian said:

The craft is actually a replica *attempt* of the original Thunderbird 3 SSTO. My main problem is that I am hoping to avoid engine clipping while avoiding any major changes in shape, which will really complicate matters.

Thunderbird3... now there's a tiny little detail that might've helped!

Why avoid engine clipping btw? Nothing about Thunderbirds ever pretended to be remotely realistic or subject to known laws of physics. Best you can do is get the shape right and make it fly - you'll not be able to replicate TB3's magic flight capabilities even with outright cheats on.

[Mr. Peabody]

1 hour ago, swjr-swis said:

Thunderbird3... now there's a tiny little detail that might've helped!

Why avoid engine clipping btw? Nothing about Thunderbirds ever pretended to be remotely realistic or subject to known laws of physics. Best you can do is get the shape right and make it fly - you'll not be able to replicate TB3's magic flight capabilities even with outright cheats on.

I suppose that you are right. It's just that I've always considered clipping engines and tanks clear into each other as sort of cheating. Nvm though. If I can make it fly and look good clipping will not be a major problem for me.

[dire]

If you really want a Thunderbird-3 the fan wiki says it's got a takeoff weight in the range of 500-600 tons and is powered by a massive nuclear reactor (those fins are supposed to be radiators). It's supposed to have chemical suborbital boosters, then is powered by ion drives (powered by the nuka-cola I assume). The wiki also says it's only 200 feet tall, though, and I feel like that is too short for its nominal mass.

[dire]

https://kerbalx.com/direstorm/Thunderbird-3

OK so instead of going with an exact visual replica, I decided to create a vehicle with approximately the size and mission profile of the Thunderbird-3. The nominal size I aimed for was about 500-600 tons on the launchpad with height of 287 feet and width of 83 feet. What I wound up with weighed 765 tons on the launchpad, has a height of 40 meters (130 feet), a width of between 17 and 19 meters (56 to 63 feet). Regarding the visual profile, I should move some tanks from below the bulb to above the bulb in order to give the right sort of visual profile, but I was having trouble finding the right parts to mate with a 2.5 meter quad-coupler.

The mission profile calls for chemical rockets to reach orbit as well as a large nuclear reactor powering ion thrusters for travel outside the atmosphere. Looking at the design of the craft, the radiator fins mark where the reactor is. The large bulb below that has to be chemical rocket fuel and/or cooling water for the reactor (if it has a SCRAM while landed, it'll drop into a water bath to try and cool it long enough for an emergency team to react, which depending on the rocket fuel that can serve double duty). The small side engines have some sort of feeding system from the reactor, so those are probably the ion engines getting fed particles and power from the reactor. The bottom of the bulb is the most logical place for the chemical stage since that's where the fuel should be, but I don't see chemical engines there. 

What I wound up with is NERV engines under the bulb (and you can tinker with it to make it more bulb-shaped if you like), and chemical rocket pylons with structural reinforcement instead of feeding tubes connecting them to the main body. The rocket is ISRU-capable, but you probably want to try that on Minmus instead of the Mun, and make sure you bring enough snacks for the process. If you make the bulb wider and fatter you can make the pylons smaller since they'll feed from it, but I was getting tired of trying to find the right adapters, so good luck. You can also move tankage from the pylons into the main rocket above the bulb to help give the right visual ratios, I was more interested in getting it into space but there's definitely a lot of room for improvement on the aesthetic.

The mods on the rocket are Engineer (for delta-v numbers), a reactor from USI Kolonization (UKS / MKS), probably a snack tin from Snacks somewhere, and Near Future Launch Vehicles, which I think is just for the fuel tanks in the bulb portion of the ship.

Trying to fix the feature ratios of the ship but it's running into classic Tall Ship Syndrome. Still working on it, probably just needs more struts and boosters.

Edited November 3, 2018 by dire

[dire]

OK this version is visually a lot closer to the canon rocket, but flying it is not for the faint of heart; it has a bad habit of flipping tail-first at the slightest provocation and I'm not really sure how to move its center of drag behind its center of mass. It -can- get to orbit, and it has tons of delta-v (and even oxidizer) left over to do interesting things once it is in orbit, but I'm not going to make any promises about the return back to the Space Center.

https://kerbalx.com/direstorm/Thunderbird-31

Edited November 4, 2018 by dire