B9 SSTO w/ VTOL

[endl]

so im using the airintake VTOL from B9 ive built a decent amount of intakes and im using two sabre 6 for the final phase but i cant gain any speed during my run up, my question is are the b9 vtols only usable in low altitude? without them i dont have enough thrust from my remaining engines. adding more intakes doesnt seem to help

Edited October 7, 2014 by endl

[Taki117]

With B9 (And I am assuming you are also using FAR) each engine can only provide so much thrust. What thrust is is the engine pushing air at a certain speed out the back of it. When the speed of the aircraft matches the exhaust velocity of the engine the engine stops providing thrust (there are other factors involved but that's the main point) VTOL engines are designed to allow you to lift off vertically and transition to a relatively low speed horizontal flight, not get to to space on their own. Also note that with FAR jet engines of any kind have massive thrust fall off after about Mach 4.

[endl]

not using far, and im using sabre s for the orbital insertion. my problem is that the speed run part the engines are dying out even with intake spam design at low alt (10-15k)

[Hodo]

not using far, and im using sabre s for the orbital insertion. my problem is that the speed run part the engines are dying out even with intake spam design at low alt (10-15k)

This is your issue. B9 is designed for FAR, not for use without it.

Here is what my heavy VTOL SSTO design currently looks like with B9 parts. It is not my largest SSTO or my best VTOL but it is something new'ish from me.

Javascript is disabled. View full album

The trick is finding that perfect thrust to weight ratio and the ascent angle.

I highly suggest if you are going to continue to use B9 parts you get FAR, as it is required in the B9 first page post.

[endl]

This is your issue. B9 is designed for FAR, not for use without it.

Here is what my heavy VTOL SSTO design currently looks like with B9 parts. It is not my largest SSTO or my best VTOL but it is something new'ish from me.

The trick is finding that perfect thrust to weight ratio and the ascent angle.

I highly suggest if you are going to continue to use B9 parts you get FAR, as it is required in the B9 first page post.

this problem has nothing to do with whether i am using near or far. the engines are winding down with high airflow still and low altitudes. they are rated for 100 thrust im getting 40. i dont know if they are hard coded to not be useable at higher altitudes unless its the oxidizer version.

[Stratzenblitz75]

The B9 VTOL engines are intended mainly for landing and takeoff; they'll lose power under high mach, or in thin atmosphere. I think if you right-click the engine from the part-selection menu, it will tell you its optimal speed. (for example, the SABRES have an optimal speed of mach 5.6).

[endl]

ok well now im even more confused by b9 it doesnt work better with near or stock installed in fact now my saber engines are running on low thrust when they should be at full power with closed cycle enabled

i cant increase the throttle they are behaving like intake engines.

[Hodo]

ok well now im even more confused by b9 it doesnt work better with near or stock installed in fact now my saber engines are running on low thrust when they should be at full power with closed cycle enabled

i cant increase the throttle they are behaving like intake engines.

http://i.imgur.com/eIlyb8u.jpg

Ok first I am going to say.

Use of FAR does matter, it even says so in the B9 forum thread first post.

Second, you are showing the correct power output for an engine that is throttled back. You have MJ set to prevent overheats and limit to terminal velocity. so it is doing those things. Try turning those off.

[endl]

Ok first I am going to say.

Use of FAR does matter, it even says so in the B9 forum thread first post.

Second, you are showing the correct power output for an engine that is throttled back. You have MJ set to prevent overheats and limit to terminal velocity. so it is doing those things. Try turning those off.

near is the same code as far it just has some of the more advanced stuff removed, i.e. the air density and drag changes are still implemented which is the key point b9 tries to push when telling people to install it.

my engines are not overheating as you can see to your left

[How2FoldSoup]

near is the same code as far it just has some of the more advanced stuff removed, i.e. the air density and drag changes are still implemented which is the key point b9 tries to push when telling people to install it.

my engines are not overheating as you can see to your left

Hodo is not trying to say that your engines are overheating, because clearly they are not. What he is trying to say, is that you have mechjeb set to autoadjust your throttle to prevent your engines from overheating. This makes sense because as you say, they are not over heating. If you look at the throttle of your engines in that screenshot you will see the throttle at about 10% thrust. Hodo was attempting to tell you that the thrust you are getting is about right for your throttle being at 10% thrust.

I hope that clarifies things

Edit: Hodo, where did you get those sweet hangers that are alongside the landing strip?

[endl]

thank you captain obvious, did you know that when mechjeb is controlling throttle for overheats it indicates this by turning the text green, as i said its not mechjeb

[Hodo]

Hodo is not trying to say that your engines are overheating, because clearly they are not. What he is trying to say, is that you have mechjeb set to autoadjust your throttle to prevent your engines from overheating. This makes sense because as you say, they are not over heating. If you look at the throttle of your engines in that screenshot you will see the throttle at about 10% thrust. Hodo was attempting to tell you that the thrust you are getting is about right for your throttle being at 10% thrust.

I hope that clarifies things

Edit: Hodo, where did you get those sweet hangers that are alongside the landing strip?

How2FoldSoup, Kerbinside plugin, it adds a bunch of extra stuff around KSC, and on Kerbin in general.

[Hodo]

thank you captain obvious, did you know that when mechjeb is controlling throttle for overheats it indicates this by turning the text green, as i said its not mechjeb

I was trying to help by pointing out possible problems, but seeing as you know all and are aware of all, then you sir can figure it out on your own.

And MJ doesn't always turn green when that mode is active, the limit to terminal velocity is most likely the issue. Seeing as MJ and NEAR or FAR for that matter doesn't work 100%.

[Taki117]

thank you captain obvious, did you know that when mechjeb is controlling throttle for overheats it indicates this by turning the text green, as i said its not mechjeb

If you have Mechjeb set up to prevent jet flameout it will still adjust your throttle to keep the sabre engines from switching modes. Mode switching is best done manually if you are having MechJeb pilot your aircraft. I also advise against using the ascent guidance for flying a spaceplane as generally they require more specialized flight profiles which Mechjeb's Ascent Guidance cannot provide.

[endl]

If you have Mechjeb set up to prevent jet flameout it will still adjust your throttle to keep the sabre engines from switching modes. Mode switching is best done manually if you are having MechJeb pilot your aircraft. I also advise against using the ascent guidance for flying a spaceplane as generally they require more specialized flight profiles which Mechjeb's Ascent Guidance cannot provide.

mechjeb flameout settings do not interfere with hybrids once they are switched over to rocket mode, also i was flying this on manual. this isnt a mechjeb problem, FAR/NEAR problem it is a B9 problem so please stop giving me "help" if your guessing.

[Specialist290]

Friendly moderator reminder: Let's try to keep the snippiness and snide remarks at a minimum, please

[technicalfool]

I'm not sure what the problem is, but I am pretty certain that the tone of this thread is dropping like a brick.

Do try to remain polite. I wouldn't like to see the thread locked before the problem is solved.

[aakerjohn]

This is your issue. B9 is designed for FAR, not for use without it.

Here is what my heavy VTOL SSTO design currently looks like with B9 parts. It is not my largest SSTO or my best VTOL but it is something new'ish from me.

http://imgur.com/a/UWsRB

The trick is finding that perfect thrust to weight ratio and the ascent angle.

I highly suggest if you are going to continue to use B9 parts you get FAR, as it is required in the B9 first page post.

Hey Hodo, i know this post is a bit older but do you still know what engine you used between the two SABRE Ms and what wings you used?

[How2FoldSoup]

Hey Hodo, i know this post is a bit older but do you still know what engine you used between the two SABRE Ms and what wings you used?

Before it gets locked for necro - the wings are the stock b9 wings most definitely. The engine looks like one from the interstellar mod. I can't tell for sure since there isn't a clear shot of it.