SSTOs and delta v

[seaces]

OK I know by looking at delta v map that a tocket to 80km LKO needs around 3400m/s. However I am left to wonder if that number is lower, same or higher for SSTOs. I have no idea and to be honest I am just getting into the SSTO and still have much to learn and this question crossed my mind.

[Oafman]

Deltav for SSTOs is generally much more complicated, because they typically have engines with different modes. Rockets tend to just use rocket fuel, so have a fixed amount of deltav to start with, while SSTOs normally use jet engines, before switching to rocket fuel. 

Jets always give you 1000s of m/s of deltav, which is the most (i think) that you can get out of them given the available liquid fuel and maybe optimised cruising altitudes and throttles etc (anyone know how the MJ/KE Deltav calculations work?) . But that liquid fuel also includes the fuel you're saving to fire up your rocket engines when you make your push for orbit, so lock those tanks if you want an accurate calculation. 

Someone will hopefully reply with a much more scientific approach to this than me, but my rules of thumb are as follows: Have enough LFO to give 1km/s deltav, then add enough liquid fuel for about 15 mins of full throttle. I can generally get my SSTOs to a decent speed and altitude from my jets (~25km, 1.8km/s+), which is comfortably enough to then push to orbit with the 1km/s of LFO I have, and even a little left over for a de-orbit burn!

If you're new to SSTOs, there are loads of great guides on this forum and elsewhere. It's a very complicated thing to master - much more to think about than with standard vertical rocket launches - but is great fun. 

Have a look at these:

http://wiki.kerbalspaceprogram.com/wiki/Tutorial:Basic_SSTO_Design

 

 

Edited March 29, 2016 by Oafman
corrected acronym

[Nich]

DV to orbit doesn't really work for spaceplanes. You need about 800-900 LFO DV and 3000-4000 of DV but that is my style

[seaces]

22 minutes ago, Oafman said:

Deltav for SSTOs is generally much more complicated, because they typically have engines with different modes. Rockets tend to just use rocket fuel, so have a fixed amount of deltav to start with, while SSTOs normally use jet engines, before switching to rocket fuel. 

Jets always give you 1000s of m/s of deltav, which is the most (i think) that you can get out of them given the available liquid fuel and maybe optimised cruising altitudes and throttles etc (anyone know how the MJ/KR Deltav calculations work?) . But that liquid fuel also includes the fuel you're saving to fire up your rocket engines when you make your push for orbit, so lock those tanks if you want an accurate calculation. 

Someone will hopefully reply with a much more scientific approach to this than me, but my rules of thumb are as follows: Have enough LFO to give 1km/s deltav, then add enough liquid fuel for about 15 mins of full throttle. I can generally get my SSTOs to a decent speed and altitude from my jets (~25km, 1.8km/s+), which is comfortably enough to then push to orbit with the 1km/s of LFO I have, and even a little left over for a de-orbit burn!

If you're new to SSTOs, there are loads of great guides on this forum and elsewhere. It's a very complicated thing to master - much more to think about than with standard vertical rocket launches - but is great fun. 

Have a look at these:

http://wiki.kerbalspaceprogram.com/wiki/Tutorial:Basic_SSTO_Design

 

 

Thnx for the sources I will check them out for some inspiration

 

[Dispatcher]

Strictly considered, an SSTO can be a rocket or spaceplane; launched either vertically or horizontally.  However, I think most people here (including myself) tend to make spaceplanes (using air breathing and closed cycle engines) and launch them from the runway, as SSTOs.

A lot of whether or not you make it to orbit depends on your piloting skills and techniques.  I'm convinced that some people can get almost anything to orbit and back.  As for me, its hard to design and build successful spaceplanes.  Once I get them to orbit, its a fun feeling.

Good luck!

[RocketBlam]

Technically, it's exactly the same number. You need to be going a certain speed to get to orbit, and that speed is the same no matter how you launch.

If you build a purely rocket-powered spaceplane, and launch vertically, your D/V (that is, reported by whatever you use, like MechJeb or KER) will be the same, or a little higher for the spaceplane, assuming it has higher drag. 

As for hybrid planes, that use jets and rockets, the only way I've found to see if they have enough D/V is to try it. MechJeb doesn't do a good job of dividing up the two modes.

Edited March 30, 2016 by RocketBlam

[Blaarkies]

4 hours ago, Dispatcher said:

Strictly considered, an SSTO can be a rocket or spaceplane; launched either vertically or horizontally.  However, I think most people here (including myself) tend to make spaceplanes (using air breathing and closed cycle engines) and launch them from the runway, as SSTOs.

A lot of whether or not you make it to orbit depends on your piloting skills and techniques.  I'm convinced that some people can get almost anything to orbit and back.  As for me, its hard to design and build successful spaceplanes.  Once I get them to orbit, its a fun feeling.

Good luck!

Try taking inspiration from real planes. I have been trying a lot of things that works well in my mind, but is barely controllable in-game. So I tried building a Skylon. I was forced to modify slightly because of tech tree limitations and parts, and on the second test flight I got orbit. I was a strange feeling since it was way easier than it should be...made me worry about re-entry. But no, on re-entry it held a 30' Angle of attack with no problems(later test flights i got it up to 60' and it still didn't feel flippy). Needless to say it became my default launcher for getting 5ton payloads into space...gonna try a bigger one next

[seaces]

Thnx on your help guys!

[Foxster]

SSTOs and planes in general can be a bit of a dark art in KSP. There are lots of rules-of-thumb that are useful to discover.

Unlike rockets, it's not easy to look at the numbers from KER or MJ and know a winged craft will fly or make orbit. There's stuff that remains hard to model before flight, like drag of the different parts at various AoA and altitudes, the complicated flight profile of an SSTO and the varying weight distribution.