Ultra Heavy Launch Vehicle Development

[Axiom]

I've been (and still am) working on a Ultra-Heavy Launch Vehicle. I want it to be able to be modular, so it can be scaled down to lift only 1.25 kilotons, or scaled up to launch 5 Kilotons

First attempt was Star- Piercer:

It failed because the fairings in the first and second stages were suprisingly heavy, and it just didn't have enough Delta-V to reach orbit with a 1.25 Kiloton load

It also had problems with phantom heat, which is a bug which causes engine heating hitboxes to spazz out and heat things they aren't supposed to.

After this I decided that the 1.25KT iteration will have engines with heat (as the problem is fine with rockets of that size), but taller ones (especially the 5KT version) will have engine heat disabled for my sanity.

Second Attempt was Tiamat:

Unlike Star-Piercer, it had an array of frontier engines that were off during launch that turned on after the detatchment of the primary booster to make the core more efficient. I did this to keep the amount of engines on at any one time to a minimum

It failed because the boosters ran out too early and the core didn't have enough TWR to fight gravity, so we lost a lot of Delta-V and it crashed

I'm currently working on a third attempt called Ragnarok

 

[Hamed]

That one was Nice

 

[Axiom]

I've made 3 prototypes for my launcher, the one that does the best will be the base for the actual launcher

 

[Axiom]

Results:

This was interesing, I think that what happened is that Reggie 1 had it's boostets separate last so it was able to fight gravity for the longest amount of time. I also tested this theory with another rocket of mine:

This is kratos, it separates it's boosters much later than any of the Reggies and was more easily able to get into orbit as it fought gravity better

So I think I have 2 options:

1. Make the core more powerful so it can fight gravity better
2. Make the core smaller and boosters larger so the core can be released at a more optimal time

 

[Axiom]

I also could just make the rocket have a very high inital TWR so the latter stages have more time to burn to get into orbit (kinda like Altaïr 's Voyager quest mission or Astro826's max payload fraction to orbit rocket)

If anyone has any advice that would be appreciated

 

[Darthan]

You could use a 2x staging ratio (each stage is twice the weight of all the stages above) so the total weight of the rocket increases 3x with each stage added - I think this is close to an optimum (balancing TWR and delta-V) with wet mass/dry mass approximately 2.8 (close to e). I've also used a 1.25 staging ratio in Normal mode - sufficient to get a 2 stage rocket to LEO (only just if high thrust/ low efficiency engines are used in the upper stage). With 1.25 and high-efficiency/low thrust upper stages you may need to do some 'apoapsis-surfing' to get the rocket into orbit - point the rocket up to 30 deg above prograde and adjust to keep as close to (or slowly moving towards) the apoapsis. When close to orbital velocity, point exactly prograde and reduce the thrust. If close to (or at) the apoapsis at this point you can get a nice circular orbit.

 

[Axiom]

You could use a 2x staging ratio (each stage is twice the weight of all the stages above) so the total weight of the rocket increases 3x with each stage added - I think this is close to an optimum (balancing TWR and delta-V) with wet mass/dry mass approximately 2.8 (close to e). I've also used a 1.25 staging ratio in Normal mode - sufficient to get a 2 stage rocket to LEO (only just if high thrust/ low efficiency engines are used in the upper stage). With 1.25 and high-efficiency/low thrust upper stages you may need to do some 'apoapsis-surfing' to get the rocket into orbit - point the rocket up to 30 deg above prograde and adjust to keep as close to (or slowly moving towards) the apoapsis. When close to orbital velocity, point exactly prograde and reduce the thrust. If close to (or at) the apoapsis at this point you can get a nice circular orbit.

Yeah thanks, but I find that method is good, but doesn't get very efficient rockets (like around 25% payload fraction). I have a rudimentary spreadsheet to do the bulk of the maths for me but I still need to make prototypes. I'm also making things kinda hard for myself by rotating engines so each engine is just a bit less efficient (that 1.5% drop in Isp really hurts for no reason).

I have 2 more prototypes in store (these should be the last ones if I'm correct)

 

[Axiom]

More prototypes!
I made Reggie 4 and Reggie 5:

And here's the results of the tests:

So very likely Reggie 4 will be the base for Ragnarok, but I want to test if the second stage needs all those engines, so Reggie 6 and & will probably have 10 and 8 engines in their second stage respectively

This also proves that gravity losses are an actual concern and proves my theory

 

[Darthan]

I did some testing with varying the number of first stage engines and asymmetric staging ratios (ratio of second stage to payload differs from ratio of first stage to second stage+payload). I used a 20% payload fraction (about 200t payload, about 1000t total launcher) and tried to see how high an orbit I could reach with each variant:

starting point
staging 1.25:1.25
4 titans lower 1.51 TWR
width 12m
3 frontiers upper 0.65 TWR
mimimal apoapsis surfing needed
872..834km orbit

reduced first stage thrust
staging 1.25:1.25
3 titans lower 1.17 TWR
width 12m
3 frontiers upper 0.65 TWR
minimum launching angle 60 (at 75 failes to reach orbit)
some apoapsis surfing needed about 10 deg above prograde
391..426km orbit

increased first stage thrust
staging 1.25:1.25
5 titans lower higher 1.92, width 15m
3 frontiers upper 0.65 TWR
apoapsis surfing done by reducing thrust not changing prograde angle
960..949km orbit reached (the winner - just)

asymmetric staging bottom heavy
top 1, bottom 1.56
4 titans lower 1.51 TWR
width 12m
3 frontiers upper 0.73 TWR
apoapsis surfing done by reducing thrust not changing prograde angle
677..685km orbit reached

asymmetric staging top heavy
top 1.56, bottom 1.0
4 titans lower 1.51 TWR
width 12m
3 frontiers upper 0.59 TWR
using minimum launcher angle 60 whin in atmosphere
apoapsis surfing needed up to 40deg above prograde
583..635km orbit reached

asymmetric staging top heavy and increased first stage thrust
top 1.56, bottom 1.0
5 titans lower higher 1.89, width 15m
3 frontiers upper 0.59 TWR
apoapsis surfing needed up to 30deg above prograde
932..961km orbit reached

Conclusion: Asymmetic staging is either worse or no better. More first stage thrust is always better, but seems to have diminishing returns closer to a starting TWR of 2.0

Last variant tried (asymmetric staging top heavy and increased first stage thrust)

 

[Axiom]

That's nice but I think that I have the scematic for the launcher I want.

 

[Axiom]

Ragnarok is here! see it's maiden flight on the Kiloton Club thread