Behemoth Development (STOCK)

[Scteam]

I decided to work on a new rocket with a huge custom stock tank at the center of it all. There isn't much more to it, this is juts gonna be a trial and error development for me.

Anyways, I decided to start out with a 2.5m tank in the middle, and put mk3 tanks around that to create a dodecagon-style (12 sided) shape. I put them in with two sets of six for the total 12 mk3 long tanks with a 2.5m long tank and a smaller sized 2.5m tank below that. The 2.5m tanks hold together the tank, and allow for easy snapping to another of the same tank. In practice this worked really well. The whole assembly is 9.6m in diameter, dwarfing even the largest stock tanks.

The next obvious step is to add a few of these tanks on top of each other and add some engines. 45 vector engines to be exact.

The rocket is huge. The 45 vector engines provide a stupid amount of thrust, but every last drop of thrust is needed to power this, as it weighs 3,141 tons. I have to use autostrut because its such a massive rocket. I would like to do it without autostrut, but it's simply much easier and straightforward to use it.

So, yeah. The first launch ended in a colossal failure. I decide the best thing to do at this point is tweak the autostrut a bit and add a nosecone for aerodynamic efficiency or whatever.

The size of this still boggles my mind. And this is just the first stage, I still want to add a second stage to make this orbit capable with a large payload.

A beauty shot. Once completed this will by far be the largest rocket I have ever made.

A beautiful liftoff!

...And another colossal failure. However, I feel like it lasted a bit longer than before.

I clearly still have a lot of work ahead. First step is making this stable. I need it to be able to expend all of it's fuel and survive ~3gs of force. So far it peaks at about 1.6gs, so a lot of work is still ahead of me. I believe the cause of this is the modularness of the 9.5m tank. If I made it one solid tank, it would probably function better.

I will keep the development updated as I go along. If anyone has any suggestions, I am open to them!

[sgt_flyer]

Hmmm.

1- how are the vectors configured ? You might want to limit the gimbal range, and even turn off gimbaling on most of them. With the COG so far away from the gimbals, lateral stresses must be simply insane

2- position of the root probe core can impact stability, leading to excessive overcorrection of SAS.

you can check by trying to fly it without sas enabled and without touching the controls to see if it survives. 

If it survives, try placing the probe core near the engines.

3- check the first item that broke in the game's mission logs (F3) (likely one of the fuel tanks) - basically one part broke free within  the clipping, leading to that RUD.

4- try to change the position of the tank onto which you applied the symmetric mk3 tanks. (Instead of on the bottom, place it on top, etc).

5- if nothing above works, it might simply be just too heavy

check by using a single column of mk3 tanks of the correct height, with the corresponding number of vectors

6- finally, if the column itself is too heavy, try to switch to a shorter core stage with fewer engines, but add boosters around it with fuel crossfeed to keep the core topped off  (you might want to use 1.25m SRBs for separatrons though ^^)

one of my old projects of the kind :

https://imgur.com/a/t5QL2

(It was able to put 1500t of oversized payload to lko ^^' before autostruts even existed thanks to a crisscrossing of struts meant to average the load) ^^

in any case, your twr might be a bit low, as your rocket is without  both upperstage and payload

Edited May 9, 2018 by sgt_flyer

[Scteam]

1 hour ago, sgt_flyer said:

Hmmm.

1- how are the vectors configured ? You might want to limit the gimbal range, and even turn off gimbaling on most of them. With the COG so far away from the gimbals, lateral stresses must be simply insane

2- position of the root probe core can impact stability, leading to excessive overcorrection of SAS.

you can check by trying to fly it without sas enabled and without touching the controls to see if it survives. 

If it survives, try placing the probe core near the engines.

3- check the first item that broke in the game's mission logs (F3) (likely one of the fuel tanks) - basically one part broke free within  the clipping, leading to that RUD.

4- try to change the position of the tank onto which you applied the symmetric mk3 tanks. (Instead of on the bottom, place it on top, etc).

5- if nothing above works, it might simply be just too heavy

check by using a single column of mk3 tanks of the correct height, with the corresponding number of vectors

6- finally, if the column itself is too heavy, try to switch to a shorter core stage with fewer engines, but add boosters around it with fuel crossfeed to keep the core topped off  (you might want to use 1.25m SRBs for separatrons though ^^)

one of my old projects of the kind :

https://imgur.com/a/t5QL2

(It was able to put 1500t of oversized payload to lko ^^' before autostruts even existed thanks to a crisscrossing of struts meant to average the load) ^^

in any case, your twr might be a bit low, as your rocket is without  both upperstage and payload

Thanks man!

I figured out the problem, it was as I expected. There was a ton of stress put through the center of the fuel tanks (the 2.5m part). Instead of stacking sections on one by one, I sort of made one giant fuel tank with the same design as the modular one. It was able to withstand many Gs of stress. I'm gonna post a few of the updates that I did here in a bit, but this is coming along rather well now that it doesn't instantly explode on the launchpad.

One thing I did update was the gimballing. I shut it off on the majority of the engines, so now only about 1/4th gimbal. I did make it shorter as well, this way I will be able to add my second stage to the rocket without many problems.

I would add boosters with crossfeeding, however I wanted to go for a BFR/Sea Dragon style rocket. I like the single core without surrounding boosters, it just looks really smooth.

Anyways thanks for the suggestions, I will definitely keep your suggestions in mind!

[Scteam]

Behemoth Booster, Mk II.

Specifications:

   Weight: 3,123 tons.

   Size: 42m tall, 11m in diameter.

   Thrust: 42,142kN at sea level.

Major changes from previous design:

Mostly just the way the fuel tanks are assembled. Instead of being put on by a subassembly, the mk3 tanks are attached together, along with the central 2.5m tanks. This provides a lot more rigidity. Aesthetically looks almost identical to the previous design.

The test launch went amazingly! The vehicle stood up to the many forces acted upon it. It managed to boost itself into the high atmosphere, and then perform a retroburn to test how many Gs it could take. As seen in the last screenshot, it took about 4 Gs, which is more than needed from it. The Mk II is a success, but there are design changes that need to be made.

 

Behemoth Booster, Mk III.

Specifications:

   Weight: 2,401 tons.

   Size: 32m tall, 11m in diameter.

   Thrust: 42,142kN at sea level.

Major changes from previous design:

The booster itself was shortened, using 3 mk3 large tanks instead of 4. This gives it the ability to hoist a second stage with a large payload high up. This is the only major difference, however in high altitude testing a shroud was used for a more aerodynamically efficient shape.

Test 1: Altitude test.

The booster managed to get itself into orbit with fuel remaining! This is a resounding success!

Test 2: Weight test.

Basically this test is designed to see how much weight it can lift at liftoff.

The test could carry 500 tons with ease at launch. The vehicle was subsequently crashed into the VAB, due to the fact that some kerbals on the development team decided there was an acute lack of explosions.

It was decided to use a prototype Mk I crewed capsule to go on top of the Behemoth Mk III booster. A shroud was added to the booster to provide protection to the engines of the capsule, along with separation components. The capsule itself weighed 700 tons, which would help test the limits of the booster. The height of all of it put together is 56m.

As seen from this photo, together the ship is massive. The whole assembly is noted for lagging the flight computers, however the design is stable enough that it doesn't matter much.

It should be noted that there aren't any kerbals on board for the test launch.

Clean separation! Powered by 6 Rhino engines, this has a high thrust with a high ISP.

The capsule has achieved orbit! At this point I reverted the flight, because as said before, this is a prototype of the first iteration. This launch was more to test the abilities of the rocket than it was to have a working manned capsule design. This will be the basis of the rest of my designs, both cargo and manned second stages.

 

I will be conducting more tests today, mostly to the second stage ships. The first stage could possibly be recovered in the ocean, however the whole craft likes to be possessed by the kraken when it touches land at really any velocity.

[Scteam]

Behemoth Cargo Ship + Booster

Specifications:

   Weight: 2,845 tons.

   Size: 59m tall, 11m in diameter.

   Thrust: 42,142kN at sea level (booster).

Notes:

Can bring approximately 300 tons to orbit without any issues.

The test launch went well. A dummy payload of 272 tons was launched into orbit.

Gene decided that, due to having excess fuel in the stage, that an experimental landing was in order.

Gene forgot to retract the solar panels however, and they were lost to the intense heat and pressure. Totally not blaming a kerbal for my own oversight.

The landing went well, however it started to roll.

Hope that wasn't something important.

The engines weren't that important... right?

 

Behemoth Crewed Ship + Booster

Specifications:

   Weight: 3,111 tons.

   Size: 58m tall, 11m in diameter.

   Thrust: 42,142kN at sea level (booster).

Notes:

Can bring 192 kerbals to orbit, no problem. Has enough fuel remaining in orbit to go to the mun or beyond. You'll probably want to refuel once you get there however.

There were a few hiccups during the test launch, however these are just pilot errors that can be fixed no problem.

This was the main issue I was talking about. The trajectory was too shallow and we picked up some heating on the way up. Nothing was damaged, so it was all good. Should be avoided in the future, though.

I honestly never get tired of watching the booster fall away and the ship flying away with it's 6 rhino engines. It's beautiful.

A good orbit was achieved. It was decided to attempt a deorbit burn as well, as this is really the only way to get the crew back.

Mission control noted that this could heat a big oven to bake snacks for the crew. Future improvement?

A good landing in the desert!

 

Alright, so the designs have been completed for the most part. I plan on creating a new forum to give the rocket a better showcase, and I'll put a download link there.

One last thing I want to note is that it is entirely possible to recover the first stage as well. The booster could easily be brought back to the ocean to land. If you land slowly into the ocean and spam the recover button, you'd probably get it back without losing many parts.