Trying to make a super heavy ssto to mun

[Leganeski]

24 minutes ago, GradientOGames said:

so use nerves during launch, or at like, 27k altitude?

Definitely not during launch. NERVs are much less efficient than RAPIERs in air-breathing mode, so the purely air-breathing stage of the ascent should last as long as possible. I usually turn the NERVs on when the RAPIERs drop below about 4 m/s² of thrust on their way to flaming out. The exact altitude depends on the ascent profile, but it's usually at about 22-26 km.

[miklkit]

How many NERVs to have?  It depends on the weight of the craft.  Under 200 tons 4 should be enough to overcome Mun gravity after using Rapiers to slow down.  Over 200 tons needs 5 for sure.  Maybe the tipping point is 190 tons.

Fine tuning your ascent profile is vital to getting into orbit.  I like to pause at 8000m and level out in order to build up lots of speed, then let it climb up.  When it stops accelerating I switch modes and light the NERVs.  When the AP hits 50 I shut down the Rapiers and go prograde to 80k.  Then circularize.  There are lots of different methods and this is just what I am using now. 

[GradientOGames]

Update and problem: I was going well and I was experimenting with using nervs to get to orbit as well. I added my 20t payload and replaced a rapier with a nerv because it weighs more than 200t in total. But now the craft won't go past subsonic speeds. I'll try adding 4 more rapiers (two on each side) and see if it makes much of a difference. How do I overcome this problem?

Although my original plan was to use the ssto for recovering something from the mun, but I'm also going to use this to add more segments to the KISS (kerbin international space station) and maybe even the MISS (MInmus space station) if I have enough delta V. An unrelated question: at what distance should u stop using sstos and start using rockets to build space station and outposts? I assuming out of the Kerbin system would be inefficient or are sstos only usefull for kerbin orbit and maybe mun (ssto does stand for single stage to orbit after all).

Thanks to the people who are sticking by to help me with sstos, I really appreciate it.

Thanks.

Edit: I added the 4 extra rapier boosters and did a few flights to see how much oxidizer I would have left after doing that nerv to orbit technique and it left me SIX THOUSAND oxidizer left. After rooming approx 4000-5000 of that, I added effectively 1000 delta V to my craft (thats including 20t payload which wont be used on mun rescue). I try to go to mun and back with it and see how it goes.  

Edit x2: what... less gooo, after getting into orbit with my new iteration, I'm left with 3600 Delta V left! I think I should add radial decouplers onto the rapier boosters to increase my speed and get rid of excess mass but I haven't seen any designs do such a thing, should I?

 

TLDR: My two (potentially final) questions are:

• at what point should I stop using sstos to build space stations (I'm assuming out side of the kerbin system is useless)
• Should I decouple my rapier boosters after using them (after transferring their spare liquid fuel to the main tanks, of course)

Edited December 4, 2022 by GradientOGames
WTFFFFF

[miklkit]

How many Rapiers does that thing have now?  My formula is 8 Rapiers and 5 NERVS and this works up to 242 tons, although that heaviest one does struggle to get supersonic.  The lightest ones fly almost like MK1s.  It could be some parts have become misaligned and are creating drag, or an engine is now occluded and is not giving any thrust. 

Using a spaceplane to recover stuff works fine.  I have an ore carrier that carries up to 3000 units of ore back to Kerbin.   Hauling cargo out is another story tho.  Build a base on Minmus to refuel and the whole system opens up for exploration.  My furthest base is on Bop.  I use rockets to get the mobile science lab and the fuel trucks out there and spaceplanes for everything else.

You will need those Rapiers for landing and takeoff on the Mun.  It has real gravity.  You will be surprised at how much fuel you will need there.

[Leganeski]

15 hours ago, GradientOGames said:

Should I decouple my rapier boosters after using them (after transferring their spare liquid fuel to the main tanks, of course)

Keeping the RAPIERs attached decreases the range of the plane somewhat, but it allows you to make multiple trips without having to rebuild it each time. Once you set up some mining infrastructure, you could even take the same plane to Laythe!

Edited December 4, 2022 by Leganeski

[GradientOGames]

Another update: I've found a few fundamental flaws, speed with nervs is INCREADIBLE slow, at this point, it'd be easier to land on minmus, also the low landing gear, I will lower the landing gear to a proper height and I'll see if I can manage my own delta V better. What are you experiences with using nervs, and any new tips with them?

Edit: new update; SSTOs are USELESS, I see that they are a lot cheaper for career, but there is absolutely no other benefit, Spaceplanes and rockets are good enough for me! I did manage to go to the mun and back with my ssto but after aerobraking, I was unable to regain control of my craft, how to be able to regain control after aerobraking on kerbin? At least I now know the ins and outs of heavy sstos. Consider this forum answered (after the next two questions of course)

 

• What are you experiences with using nervs? and any new tips with them?
• How would I be able to regain control of my ssto after aerobraking (altitude 8k with 200-300mps) Final Craft Image
• Give me one reason for me to use sstos (excluding cost)? If not, then WOOHOO!

Thank you all for sticking around <3 (no homo)

Edited December 5, 2022 by GradientOGames
Update

[miklkit]

Ah, now on to the next series of questions.  

For the Mun I use Rapiers to slow down and then land with NERVs.  For takeoff everywhere I use Rapiers and in vacuum NERVs too.  The vectored thrust is vital.  For Minmus NERVs are good enough because of the low gravity.

Now you have found the hard part about doing spaceplanes.  Going up isn't hard, but getting back down is.  They have to be balanced like an airplane under all conditions.  Full and empty fuel tanks and full and empty cargo bays.  This one is a rover carrier after it dropped the rover off at a base on Bop.  Without that weight it went unstable and decided to fly backwards.  So......I tried to land it like a rocket and almost succeeded, but it laid over on its side right at the end and knocked a wing off.

I built my first MK3 in KSP ver. 1.11.  I'm still learning and the designs are evolving.  IMO rockets are better for heavy loads and spaceplanes are better for everything else.

[Leganeski]

18 hours ago, GradientOGames said:

What are you experiences with using nervs? and any new tips with them?

If you only use nuclear engines on a stage, your TWR will be a lot higher, both because you can fit more of them and because you aren't carrying as much dead weight in the form of other engines. NERVs alone can comfortably land on Mun, and can lift a small payload off of Duna with some difficulty.

I somewhat recently built a rocket powered by more nuclear engines than I probably needed. Towards the end of its mission, it was almost entirely fuel tanks and engines with very little payload, but it could take off against a surface gravity of 0.4 g and had over 8000 m/s of Δv in its single stage.

 

19 hours ago, GradientOGames said:

How would I be able to regain control of my ssto after aerobraking

I've run into this problem so many times that in quite a few cases, I just gave up and stuck a pair of parachutes on the wings.

 

19 hours ago, GradientOGames said:

Give me one reason for me to use sstos (excluding cost)?

If you want to to do a grand tour where you land on multiple large planets or moons in one mission, SSTOs can be a good way to do that without having to build a separate lander for each one. (This is more relevant in modded systems with more atmospheres. For instance, I built this plane as an SSTO so that I could use it for not only Kerbin and Laythe but also two other similar planets from planet packs.)

Outside of that, I don't really see much use for SSTOs either.