New player; How to get to orbit with the Dv suggested in the Dv Maps?

[MoridinUK]

So I actually want to try to stay under 340m/s for most of my ascent? Until I'm in the upper atmosphere? or at least out of the thick bit (around 30km) where my rocket normally looks like it has already blown up?

And gentle turns, closer to pro-grade, are less wasteful than cranking over and hitting the throttle!

Yes real life, or even earth like sim, must be much harder, Kerbin's atmosphere is smaller right?

 

Also, snark, sorry for kinda doing the, "just let me google that for you thing" , I must have been having a lazy moment sorry...

 

[Plusck]

Well, yes and no (of course! when make an answer simple if it can be complicated!).

Up to about 8-10km, you definitely don't want to break the sound barrier because the atmosphere is so thick. But you most definitely want to do so by 30km - much earlier than 30km in fact - because otherwise the time you take to get to really thin air (i.e. about 33-35km) is robbing you of enormous amounts of energy.

Trial and error is the best way to get a feel for it. And as I said earlier (or hinted at, I suppose): beware of getting into bad habits. I went through a phase of station-building which required a much slower ascent to start with, because my payloads were draggy and my engines a bit feeble, so I got used to going too slow and making much more of an effort over a very long time in the very high atmosphere. So now I'm re-learning how to be more efficient, but since it's hard or even impossible (without mods) to watch all of the information closely all the time (altitude, speed, navball inclination, remaining fuel in stage, Apoapsis, time to Ap, drag/heating effects on your ship) then you need to get a feel for it. I'm sorry if that means that I'm not giving hard numbers but I'd have to video a good launch and run back over it to be more precise about them.

[MoridinUK]

It's all good!  So stay below the sound barrier below 10km, break it in good time for 30, hmm that is much slower than I'm currently doing.  I may aim for a 15k sound barrier and then crank it up... In my current ship that would mean burning up the srb, and then throttling back the 2nd stage in order to just keep ticking over and start to build up once over 10-15km to punch through the sound barrier...,, Someone did say my rocket was over powered huh?

I think I could unlock the terrier, is it worth using that post 35km or only once in space or on it's edges?  

[Plusck]

No, no, no...

Sorry, but when I say "about" I reallly mean "about".

I went back to my copy of your first craft (with two goo cannisters on the roof).

Best orbit so far: 71x76 km with 15 units of LF remaining.

This is a screenshot at the sound barrier on that run: 7km, 5/6th thrust, 55° prograde. Just after this shot was taken I cranked it up to 100% thrust.

Spoiler

So in fact, this ended up getting very fast and hot at around 20km. Maybe I can improve the launch profile to lose less energy to the atmosphere but so far, since your craft is actually very stable at prograde, it seems atmopheric losses are more than compensated for by the savings on gravity-over-time losses.

Edited December 12, 2015 by Plusck

[Plusck]

Aaaaaand finally...

Nope, can't really do better than that. I've tried a ton of variations but SRB at 100%, breaking the sound barrier at around 6800m at 50°, and getting very hot at around 20km, and ending up with a very minor (around 600m/s) circularization burn leaving 15 units LF in the tank, is the best I can do.

I did get a bit better by being even more aggressive - breaking the sound barrier earlier at closer to 45° around the first stage switch, and ending up with 25 units fuel, but the goo cannisters exploded because I was doing 1800m/s at 30km... Pics here: http://imgur.com/a/tQPzL

Oh and, for that last run, I left SAS off all the time and didn't touch the controls at all (after initiating the turn) until the second stage ran out. After that it is necessary otherwise you flip.

 

And finally finally finally, a fully documented best orbit while keeping the goo in one piece. I tried to make sure every significant moment was pictured. Again, didn't use SAS or touch the controls between the off-launchpad manoeuvre and the start of the last stage. http://imgur.com/a/QihYN

Edited December 12, 2015 by Plusck

[MoridinUK]

Ok so in my aero-dyanmic 'bolt' I should just enjoy the speed... lol but draggy things, like a space station on the end, I'm going to have to take it easy right?

I'm soon going to be launching Sats, and I kinda need them to not blow up on the way up!  Sigh... Are there any stock fairings? Or any advice on that? 

Thanks for all the help though... at the moment I'm trying to get up with a very similar rocket and a heat shield for a contract... I'm not making it happen so far! 

 

[Plusck]

Fairings aren't quite fixed yet. Apparently they protect from heat, but they don't really protect from drag, so you might be better off simply not using them. I don't really know because I haven't used them since 1.0.4.

[MoridinUK]

Well burning goo off is one thing, but burning scanners and solar panels off sats would rather defeat the point lol!

[Snark]

56 minutes ago, Plusck said:

Fairings aren't quite fixed yet. Apparently they protect from heat, but they don't really protect from drag, so you might be better off simply not using them. I don't really know because I haven't used them since 1.0.4.

They do protect from drag.  However, they have a bug that causes them to generate a big lift vector really out at the forward tip, which can make rockets flip-prone.  Doesn't mean you can't use fairings (I use 'em OK), just means that you shouldn't have a great big long enormous one, and make sure you have plenty of fins / gimbal / whatever else to provide aero stability.

[Snark]

4 hours ago, MoridinUK said:

It's all good!  So stay below the sound barrier below 10km, break it in good time for 30, hmm that is much slower than I'm currently doing.  I may aim for a 15k sound barrier and then crank it up... In my current ship that would mean burning up the srb, and then throttling back the 2nd stage in order to just keep ticking over and start to build up once over 10-15km to punch through the sound barrier...,, Someone did say my rocket was over powered huh?

I think I could unlock the terrier, is it worth using that post 35km or only once in space or on it's edges?  

The Terrier is your friend.  The biggest single wrong thing I've seen with the designs pictured in this thread is that there's a Reliant-or-Swivel as an upper stage engine.  That's what's killing you; the engine just weighs too much and you don't need that much power in an upper stage.

 The Terrier is really, really good as an upper-stage engine (good fuel efficiency, weighs only half a ton).  You definitely don't want to use it at sea level, but it's just fine at anything over 15 km or so.  Bear in mind that at 25km, the air is only 1% of what it is on the ground!  Even at 10km a Terrier's usable.

Here's a handy recipe for getting to orbit:

1. Hammer, thrust tuned appropriately to give TWR of 1.5 on the launch pad.  (A Thumper would be even better, but a Hammer will do.).  If you have radial decouplers, you could mount two radial Thumpers with nosecones.
2. A Swivel with 4 tons of fuel.  (Yes, a Swivel, not Reliant. By the time the Hammer craps out, you'll be high enough that the Swivel's better vacuum Isp is worth it. Plus the gimbal helps stability.)
3. A Terrier with 2 tons of fuel.
4. Command pod with parachute.

You'll easily be way over 15 km by the time that Terrier kicks in, and the mass savings are incredible (a Terrier saves 3/4 ton of mass over a Swivel... using a Swivel or Reliant as an upper stage engine is like lugging along an extra command pod, and you don't need the thrust.  It's just dead weight.)

Launch profile is to start tipping very gently eastwards practically as soon as you're off the pad.  I mean just the tiniest of nudges, to start with.  Gradual turn, staying very close to prograde, until you're at 45 degrees at around 10 km or so, then punch it.  You should get to orbit with no problem.

Edited December 12, 2015 by Snark

[Plusck]

Yes, absolutely. Forgot to answer that bit about the Terrier. It can make a world (or at least a Mun...) of a difference.

[MoridinUK]

Cool, I never thought to use it so low down!  The Terrier was missing from the above builds because I haven't unlocked it yet! Thanks again for all the help!  I have family staying over the weekend so I'll probably have to wait to play some more!

[Snark]

The Terrier comes in pretty handy in early career games.  Not only as a great way of getting to orbit, but it's also very useful for some early contracts that ask for things like "take a crew report in flight above 18,000 meters at <some place on Kerbin>."  They're easy to do with a simple spaceplane that has a couple of Juno jets flanking a Terrier.  The Junos fly you to the site and get you to 10-12km altitude, then pull the nose to the sky and punch the Terrier; a ton or two of fuel will easily hop you up over 20 km.  Then come back down and use the Junos to fly back to base.

[MoridinUK]

So this has all been really useful!  But the contracts are driving me mad!  So many test in flight and they want a stupid alititude at a stupid speed.  Altitude 47k to 55k at 200mps.. That would mean doing a launch just for that contract... sigh...

[WuphonsReach]

I rarely do the test contracts any more, they just don't pay enough to be interesting.  Instead I focus on orbital satellite contracts, rescuing kerbals (to fill out my roster), and add-on contract packs.

(Stock "part test" contracts used to be a lot worse.  They've improved, but still need some loving from the developers.)