what am i doing wrong trying to get this to orbit?

[putnamto]

ive done it before, but my brain is stupid and i cant figure this out at all, i made mechjeb try in sandbox and he just laughs and smashes it to the ground.

ive tried launching straight up and turning horizontally, this almost worked but my pe would reach 60km then climb slower and slower and slower until around 69km it would almost completely stop moving until i run out of dv.

ive tried pitching 5 degrees off of launch, at 100m/s, and at 400 m/s, then in each of those cases killing my engine once ap is 70k+ and turning horizontal at 30s till ap and thursting, this does the same as my attempts at going straight up but this time my pe stops climbing around 50-60km and my ap starts climbing rapidly until im completely out of dv.

i guess im really just looking for some solid guidance as to what im actually doing.

and my brain is broke and i cant remember anything, ever, like i said i have flown this before successfully because of what i named it, and the fact that i have an extra kerbal.

i hate this game sometimes.

[Geonovast]

What mods are on the craft besides MJ and vaporvent?

Can you get a VAB screenshot of it?

I'm guessing it has something to do with what's underneath the nosecone at the top.  Aerodynamics hates the sudden diameter changes without a fairing.

[putnamto]

20 minutes ago, Geonovast said:

What mods are on the craft besides MJ and vaporvent?

Can you get a VAB screenshot of it?

I'm guessing it has something to do with what's underneath the nosecone at the top.  Aerodynamics hates the sudden diameter changes without a fairing.

No  other  mods  on  the  craft  that  I  can  think  of.

Under  the  nose cone  is  a  reaction  wheel  and  probe  core

[Zhetaan]

@putnamto:

You could use something more aerodynamic for the side boosters (the flat tops are draggy) but since you're only using them for twenty seconds, I don't think it's terribly critical.  You have enough delta-V to make it to orbit, assuming that you're lighting the upper stage engine somewhere in the upper atmosphere.  The thrust-to-weight is good.

I think it's a matter of piloting.  If you're launching straight up and turning horizontal, you're wasting a lot of fuel.  If you're pitching at five degrees just after launch and then going at that pitch to a 70 km apoapsis, then I think you're still wasting fuel.  I specifically think this is the case because you start burning to circularise too late; the reason your periapsis stops climbing but your apoapsis doesn't is because at the point you're thrusting, you're too far away from an apsis to get the most efficiency from the burn.  It's inefficient to do this, but if you cannot burn any earlier, then you need to put some radial-out into it, not just prograde.

In any case, what you're doing right now does not look like a proper gravity turn.  Pitch the first five degrees, but don't stop pitching.  Keep turning the rocket so that you are somewhere in the neighbourhood of forty-five degrees at ten kilometres altitude, and be rather near horizontal by the time you reach thirty or forty kilometres.  By then, it's usually easier to keep an eye on your climbing apoapsis; try to keep it about a minute ahead of you.  When you get to seventy-five kilometres, coast out of the atmosphere and then burn to circularise.  Even that is not the most efficient ascent, but it's certainly workable.

[putnamto]

39 minutes ago, Geonovast said:

What mods are on the craft besides MJ and vaporvent?

Can you get a VAB screenshot of it?

I'm guessing it has something to do with what's underneath the nosecone at the top.  Aerodynamics hates the sudden diameter changes without a fairing.

it was a battery and a probe core

10 minutes ago, Zhetaan said:

@putnamto:

You could use something more aerodynamic for the side boosters (the flat tops are draggy) but since you're only using them for twenty seconds, I don't think it's terribly critical.  You have enough delta-V to make it to orbit, assuming that you're lighting the upper stage engine somewhere in the upper atmosphere.  The thrust-to-weight is good.

I think it's a matter of piloting.  If you're launching straight up and turning horizontal, you're wasting a lot of fuel.  If you're pitching at five degrees just after launch and then going at that pitch to a 70 km apoapsis, then I think you're still wasting fuel.  I specifically think this is the case because you start burning to circularise too late; the reason your periapsis stops climbing but your apoapsis doesn't is because at the point you're thrusting, you're too far away from an apsis to get the most efficiency from the burn.  It's inefficient to do this, but if you cannot burn any earlier, then you need to put some radial-out into it, not just prograde.

In any case, what you're doing right now does not look like a proper gravity turn.  Pitch the first five degrees, but don't stop pitching.  Keep turning the rocket so that you are somewhere in the neighbourhood of forty-five degrees at ten kilometres altitude, and be rather near horizontal by the time you reach thirty or forty kilometres.  By then, it's usually easier to keep an eye on your climbing apoapsis; try to keep it about a minute ahead of you.  When you get to seventy-five kilometres, coast out of the atmosphere and then burn to circularise.  Even that is not the most efficient ascent, but it's certainly workable.

thank you, ill try that.

edit, im a horrible pilot, was looking good until my middle stage ran out at 20km, i staged and my ship started cartwheeling.

Edited March 21, 2018 by putnamto

[Zhetaan]

Now that I can see the top nosecone a little better, you should know that the aero system really doesn't like sudden diameter changes.  It's not quite so bad as a flat face, but it's something to consider:  you can put the battery/wheel pack in a service bay, a fairing, after a tapered transitional piece, or under a smaller nosecone.

[putnamto]

im switching it over to a radial mounted battery and putting it right under the can.

[putnamto]

 

[DerekL1963]

Just a suggestion...  Could you either launch during the daytime or use the ambient light adjustment in settings?  It's almost impossible to see what's going on.

From what I can see, it looks like it's spinning out of control because you haven't turned on stability control.

[putnamto]

 

13 minutes ago, DerekL1963 said:

Just a suggestion...  Could you either launch during the daytime or use the ambient light adjustment in settings?  It's almost impossible to see what's going on.

From what I can see, it looks like it's spinning out of control because you haven't turned on stability control.

sorry about that, wasnt noticeable on my screen.

but thats exactly what happens, the only way i can get the pitch down to 45 degrees is to turn off stability control, but if its off, as soon as i drop the bottom stage it spins wildly out of control(then i get frustrated and start pressing space over and over in hopes of it blowing up)

i did eventually make it into orbit with that ship and successfully rescued neible.

oddly enough rendevous with stranded kerbals seems easy(with mechjebs help) but making orbit with this ship is a pain.

[DerekL1963]

7 minutes ago, putnamto said:

but thats exactly what happens, the only way i can get the pitch down to 45 degrees is to turn off stability control, but if its off, as soon as i drop the bottom stage it spins wildly out of control(then i get frustrated and start pressing space over and over in hopes of it blowing up)

If you're using stock SAS and turn on stability control, you can control your attitude using the keyboard.   If you can't, then what are you using for stability control?

[Streetwind]

I agree, I can pretty much not see anything in the video aside from the user interface.

That said - for your rocket to flip so violently at more than 30km altitude at less than 900 m/s, despite active reaction wheels, you really have to have a massive amount of drag coming from some part right at the top. You were facing almost directly prograde, too. The only conclusion I can come to is that the probe core assembly as you have it needs to change.

Do the following:
- Put a "FL-A10 Adapter" on top of the lander can (or the decoupler, if that is a decoupler up there)
- Attach your battery/probe core to the top of that adapter
- Get rid of the nose cone
- Put a "Small Nose Cone" in its place

You can find these parts using the part search bar on top of the parts list in the editor if you don't know where they are located.

EDIT: as a bonus, use the move tool in the editor to slide the probe core and battery down into the adapter, so that the nose cone appears flush with it. This doesn't actually change anything about aerodynamics, but it will make the upper stage physically shorter, which brings your center of mass and center of pressure closer together, which (in this particular case) improves stability. Rockets fly better the more forward their main mass is situated (called "Rule of Rocketry #1: heavy bits at the front, draggy bits at the back").

Also, it looks better.  

Edited March 21, 2018 by Streetwind

[putnamto]

20 minutes ago, Streetwind said:

I agree, I can pretty much not see anything in the video aside from the user interface.

That said - for your rocket to flip so violently at more than 30km altitude at less than 900 m/s, you really have to have a massive amount of drag coming from some part right at the top. You were facing almost directly prograde, too. The only conclusion I can come to is that the probe core assembly as you have it needs to change.

Do the following:
- Put a "FL-A10 Adapter" on top of the lander can (or the decoupler, if that is a decoupler up there)
- Attach your battery/probe core to the top of that adapter
- Get rid of the nose cone
- Put a "Small Nose Cone" in its place

You can find these parts using the part search bar on top of the parts list in the editor if you don't know where they are located.

i dont have aerodynamics unlocked yet, ive tended to stay away from all of the things associated with airplanes for now.

20 minutes ago, DerekL1963 said:

If you're using stock SAS and turn on stability control, you can control your attitude using the keyboard.   If you can't, then what are you using for stability control?

sorry, was just frustrated that makes no sense.

thank you for all the help guys.

 

Edited March 21, 2018 by putnamto

[Streetwind]

56 minutes ago, putnamto said:

i dont have aerodynamics unlocked yet, ive tended to stay away from all of the things associated with airplanes for now.

Well, there are other options, but it depends on what you expect this rocket to do. For example, I see that you have landing legs, which is very unusual for a simple Kerbal rescuer. So I'm not sure of the intended role.

But if you're just looking to rescue Kerbals, a direct replacement with simpler parts would be:
- toss the lander can and everything above it
- put a mk1 pod in its place
- put the probe core and a battery on top of the pod
- put a mk16 parachute on top of it all

You now have a simpler crew-and-control section with less drag and higher reaction wheel strength, for pretty much the same mass, on the same lifter, giving you the same capabilities.

I'd probably design a rescue craft with a pilot instead of a probe core and a mk1 crew cabin for passengers, though. Lets me pick up two Kerbals in one launch, and doesn't constantly need power.

[putnamto]

5 minutes ago, Streetwind said:

Well, there are other options, but it depends on what you expect this rocket to do. For example, I see that you have landing legs, which is very unusual for a simple Kerbal rescuer. So I'm not sure of the intended role.

But if you're just looking to rescue Kerbals, a direct replacement with simpler parts would be:
- toss the lander can and everything above it
- put a mk1 pod in its place
- put the probe core and a battery on top of the pod
- put a mk16 parachute on top of it all

You now have a simpler crew-and-control section with less drag and higher reaction wheel strength, for pretty much the same mass, on the same lifter, giving you the same capabilities.

I'd probably design a rescue craft with a pilot instead of a probe core and a mk1 crew cabin for passengers, though. Lets me pick up two Kerbals in one launch, and doesn't constantly need power.

i put landing legs on it in hopes that it would save the can, and i put the can in instead of the pod to save weight(and i thought it looked cool)

ive tried the manned version with a crew cabin but ive never been able to slow down the cabin+pod enough to stop it from being destroyed on impact, and it always had a tendancy to turn prograde and speed up instead of slow down. hell ive had it continue having the aero flame effects all the way to the ground before.

i will take your advice in mind and probably redesign the top half of the craft, thank you. my next quest is to get four tourists landed on the mun, and then back again.

[Streetwind]

2 hours ago, putnamto said:

ive tried the manned version with a crew cabin but ive never been able to slow down the cabin+pod enough to stop it from being destroyed on impact, and it always had a tendancy to turn prograde and speed up instead of slow down. hell ive had it continue having the aero flame effects all the way to the ground before.

Yeah, putting the crew cabing there results in a vehicle that is not aerodynamically stable, for the same reasons I mentioned before (the mass off the reentry vehicle is concentrated on the wrong end, in the mk1 pod). However, you do have a pilot on board. And if that pilot has been to orbit at least once before, he has SAS Hold Retrograde available. I found the instability of the reentry vehicle I built to be so minor that SAS kept it straight without the slightest sweat.

Then it's all a question of slowing down. Flames all the way to the ground should never happen; you either had a bug, or were carrying a huge excess of unnecessary equipment, or were going pointy-end-first (after flipping). My craft generally slows down fine to speeds safe for main chute deployment as long as it doesn't flip. But I tend to carry a pair of radial drogues anyway, in addition to the usual mk16 main chute; the drogues are much more sturdy, and you can pop them early when you fear you are coming in too hot.

Also, yes, impact tolerance. The drogues actually help with slowing down the landing speed as well. But another key ingredient is a heat shield below the crew cabin. Not for thermal protection, but for moving some mass down to the correct end, and for its much higher impact tolerance. You can land on it, and the craft will be just fine.

Here's a screenshot I just made after replicating something akin to the rescue craft I used early in my last career. A quick test flight to a 75x75km orbit had over 800 m/s dV left, so it is easily capable of rendezvous with two separate stranded Kerbals, and the whole thing costs less than 6800 funds. I wouldn't take it beyond low Kerbin orbit though; at least, not without upgrades. A pair of Thumpers taped to the sides as a new first stage will give this thing quite a large reach, and a tiny solar panel helps keep power available on long flights.

That's a Reliant at the bottom; the heat shield has half of its ablator; the pod has its monoprop removed. You'll also notice the battery below the main chute. I usually fly without one, but I reckon you'll be more comfortable having it. I also used the move tool to nudge the pod and the crew cabin a bit closer together, and pull the heat shield a small bit away from the bottom of the crew cabin. Both of these things make the craft look better (especially the heat shield, which in its natural state clips too deep into the cabin and ends up having parts of it clip through) and slightly improve reentry stability by modifying the mass distribution. Finally, the parachutes are set to open a little lower down, because I am impatient.

Launch is as simple as throttling to 100%, setting SAS Hold Prograde, flying a standard gravity turn aiming at 45 degrees pitch between 10km and 12km, and casually strolling into orbit under Terrier power. Reentry is as simple as setting SAS Hold Retrograde and popping the chutes when it's safe to do so. (I can't advise you on MechJeb settings, as I have never used it.)

Here's the craft file, if you want to try it out. But even if you prefer your own designs, I hope it'll at least inspire you a little.

EDIT: Derp. I just realized that the FL-T800 tanks aren't really earlygame. You can of course replace them with any equivalent amount of smaller tanks, but loading the craft file might be tricky...

 

Edited March 21, 2018 by Streetwind

[putnamto]

 

13 hours ago, Streetwind said:

Yeah, putting the crew cabing there results in a vehicle that is not aerodynamically stable, for the same reasons I mentioned before (the mass off the reentry vehicle is concentrated on the wrong end, in the mk1 pod). However, you do have a pilot on board. And if that pilot has been to orbit at least once before, he has SAS Hold Retrograde available. I found the instability of the reentry vehicle I built to be so minor that SAS kept it straight without the slightest sweat.

Then it's all a question of slowing down. Flames all the way to the ground should never happen; you either had a bug, or were carrying a huge excess of unnecessary equipment, or were going pointy-end-first (after flipping). My craft generally slows down fine to speeds safe for main chute deployment as long as it doesn't flip. But I tend to carry a pair of radial drogues anyway, in addition to the usual mk16 main chute; the drogues are much more sturdy, and you can pop them early when you fear you are coming in too hot.

Also, yes, impact tolerance. The drogues actually help with slowing down the landing speed as well. But another key ingredient is a heat shield below the crew cabin. Not for thermal protection, but for moving some mass down to the correct end, and for its much higher impact tolerance. You can land on it, and the craft will be just fine.

Here's a screenshot I just made after replicating something akin to the rescue craft I used early in my last career. A quick test flight to a 75x75km orbit had over 800 m/s dV left, so it is easily capable of rendezvous with two separate stranded Kerbals, and the whole thing costs less than 6800 funds. I wouldn't take it beyond low Kerbin orbit though; at least, not without upgrades. A pair of Thumpers taped to the sides as a new first stage will give this thing quite a large reach, and a tiny solar panel helps keep power available on long flights.

That's a Reliant at the bottom; the heat shield has half of its ablator; the pod has its monoprop removed. You'll also notice the battery below the main chute. I usually fly without one, but I reckon you'll be more comfortable having it. I also used the move tool to nudge the pod and the crew cabin a bit closer together, and pull the heat shield a small bit away from the bottom of the crew cabin. Both of these things make the craft look better (especially the heat shield, which in its natural state clips too deep into the cabin and ends up having parts of it clip through) and slightly improve reentry stability by modifying the mass distribution. Finally, the parachutes are set to open a little lower down, because I am impatient.

Launch is as simple as throttling to 100%, setting SAS Hold Prograde, flying a standard gravity turn aiming at 45 degrees pitch between 10km and 12km, and casually strolling into orbit under Terrier power. Reentry is as simple as setting SAS Hold Retrograde and popping the chutes when it's safe to do so. (I can't advise you on MechJeb settings, as I have never used it.)

Here's the craft file, if you want to try it out. But even if you prefer your own designs, I hope it'll at least inspire you a little.

EDIT: Derp. I just realized that the FL-T800 tanks aren't really earlygame. You can of course replace them with any equivalent amount of smaller tanks, but loading the craft file might be tricky...

 

ill give her a whirl later, thanks.(and then i will delete it and make my own, but you know how that is)

have you upgraded to 1.4 or something? that craft isnt compatible with my version of ksp, or atleast the game says it isnt when i try to load it.

Edited March 22, 2018 by putnamto