Liquid fuel problem in ssto

[Space boy]

I am trying to make a ssto and with mk2 parts. I am using panther engines and swivel engines. When ever I fire the swivels, they start extracting liquid fuel from the panther engine fuel tanks, resulting in the oxidizer running out before the liquid fuel. How do I solve this?

[Laie]

You don't. Or rather, you "solve" this by either bringing less LiquidFuel, or more Oxidizer.

There is no easy way to match up tanks with engines, so that an engine can only drain from one particular set of tanks. It's doable, in principle, but this will impose restriction on how your vessel can be shaped.

It's easier to think of your whole vessel as one single tank that feeds both the LFO rocket motor, as well as the LF-only jets. It stand to reason that will have to put in the LFO for the rocket, and some extra LF on top of that for the jets. Question now becomes, "how much extra LF do you need?"

There is no precise way to tell ahead of time how much extra LF you will need. In order to get an approximate idea, open the resource panel and look at the numbers: how much LF have you consumed by the time you light the rockets? Bring perhaps 50% more than that number to play it safe, but everything else can be LFO.

[Space boy]

12 minutes ago, Laie said:

You don't. Or rather, you "solve" this by either bringing less LiquidFuel, or more Oxidizer.

There is no easy way to match up tanks with engines, so that an engine can only drain from one particular set of tanks. It's doable, in principle, but this will impose restriction on how your vessel can be shaped.

It's easier to think of your whole vessel as one single tank that feeds both the LFO rocket motor, as well as the LF-only jets. It stand to reason that will have to put in the LFO for the rocket, and some extra LF on top of that for the jets. Question now becomes, "how much extra LF do you need?"

There is no precise way to tell ahead of time how much extra LF you will need. In order to get an approximate idea, open the resource panel and look at the numbers: how much LF have you consumed by the time you light the rockets? Bring perhaps 50% more than that number to play it safe, but everything else can be LFO.

Then how do people people who make really complicated sstos make it work I am just trying a simple lko ssto. 

[Laie]

38 minutes ago, Space boy said:

Then how do people people who make really complicated sstos make it work

One word: Experience.
Try, modify, try again. By the time you make your tenth SSTO, you'll have much better idea about how much fuel you will need and are likely to get it right the first time. Well, about right. Which is good enough. Not all ascents are 100% perfectly the same, so a bit of a safety margin is desirable, after all.

[AHHans]

2 hours ago, Space boy said:

Then how do people people who make really complicated sstos make it work I am just trying a simple lko ssto.

As @Laie said: by thinking of their craft as one single tank with both Lf and Ox, and then balancing the ratio of those to match the ascend profile.

I personally have a good number of Mk-1 (1.25m circular) tanks in my SSTO spaceplanes, for which both LfOx and Lf only tanks exist. That way I can swap out the tanks as needed. (If I have Lf left over but not enough Ox, then swap a set of Lf only for LfOx, and so on, and so on...)

Another comment that comes to my mind is that making a SSTO spaceplane is easier using RAPIER engines, than with a panther / swivel combination. The latter is possible, but I only managed after I made quite a few other designs. (I struggled for quite some time to design a SSTO spaceplane that can get into orbit. At some time I was so frustrated that I stopped trying for a few weeks...)

[Space boy]

2 minutes ago, AHHans said:

As @Laie said: by thinking of their craft as one single tank with both Lf and Ox, and then balancing the ratio of those to match the ascend profile.

I personally have a good number of Mk-1 (1.25m circular) tanks in my SSTO spaceplanes, for which both LfOx and Lf only tanks exist. That way I can swap out the tanks as needed. (If I have Lf left over but not enough Ox, then swap a set of Lf only for LfOx, and so on, and so on...)

Another comment that comes to my mind is that making a SSTO spaceplane is easier using RAPIER engines, than with a panther / swivel combination. The latter is possible, but I only managed after I made quite a few other designs. (I struggled for quite some time to design a SSTO spaceplane that can get into orbit. At some time I was so frustrated that I stopped trying for a few weeks...)

Yes I think you are right about the rapiers. I got inspired for a panther swivel combination because of a mark thrimm video on low tech sstos. 

[magnemoe]

4 hours ago, Laie said:

One word: Experience.
Try, modify, try again. By the time you make your tenth SSTO, you'll have much better idea about how much fuel you will need and are likely to get it right the first time. Well, about right. Which is good enough. Not all ascents are 100% perfectly the same, so a bit of a safety margin is desirable, after all.

This, I'm an rocket guy I made an spaceplane as it was required to support my Laythe base. Idiotic simple design, 

3 1.25 meter fuselages, core is cockpit and two passenger modules followed by an LF tank and an material science bay and an equipment bay. 
Sides is air intake fuel and rapier, equipment bay around halfway back.

 

[Guest]

20 hours ago, Space boy said:

Then how do people people who make really complicated sstos make it work I am just trying a simple lko ssto. 

Iteration. I make an initial design with a fuel split that feels "about right." Then I fly it. If I run out of oxidiser before I make orbit, I change the split to have more oxidiser. If I make orbit with too much Lf, I note how much too much and change the ratio again so I have equal amounts. 

[Fierce Wolf]

I found that rocket-typed SSTO are easier than plane-typed ones. A few tanks, 4 bobcats on the bottom are usually enough to put a load on orbit and return. Basically no need for jets, or wings.

[Space boy]

4 minutes ago, Fierce Wolf said:

I found that rocket-typed SSTO are easier than plane-typed ones. A few tanks, 4 bobcats on the bottom are usually enough to put a load on orbit and return. Basically no need for jets, or wings.

Bobcats??! 4 of them? 

[Fierce Wolf]

2 hours ago, Space boy said:

Bobcats??! 4 of them? 

Go hard or go home buddy! lol