I can't figure out my attitude

[JoeSchmuckatelli]

3 hours ago, KrisKelvin said:

Err... yes! What do you think I've been doing all this time! I assumed that was the only way of steering!

I'm afraid I don't know any of your abreviations. OKTO, IOW?

OKTO is the octagonal shaped probe core.  It's found in the Pods section in the VAB /SPH.  It can be used for a pilot or to drive an unmanned satellite or rover. There is also a HECS which has six sides.  I like the OKTO because it has more - and the OKTO2 is even moar bettah! 

 

IOW = In Other Words. 

Re: manual control... The technique used between shooting straight up and driving the nose to turn 90 differs from keeping the pip manually in the prograde circle via tapping the keys during a successful gravity turn - that's what I was trying to illustrate 

[Zhetaan]

17 hours ago, KrisKelvin said:

Looking at the video Joe posted above, I see you can lock the steering to the prograde marker! That's cool. I did wonder what those things on the left of the navball were!

Although I just tried that and it doesn't get you into orbit! I was still only pitched over about 10 degrees at 100km altitude!

So when would you use that?

You keep asking all of the simple questions that have complicated answers.

Prograde hold attempts to ensure that your rocket follows a smooth transition between near-vertical and near-horizontal flight.  The idea is that as you ascend, gravity warps your rocket's trajectory and pulls it down, but also as you ascend, your increasing speed in the horizontal direction keeps your nose from pointing below the horizon, and the resultant of this is that you end up in orbit before you do your very best impression of a javelin.

Sometimes, it even works that way.

However, it is not a 'click this button to reach orbit' control; the only thing that 'gets you into orbit' is your ability to design and fly the rocket.  Prograde hold can be part of that design, but you need to activate it at the correct time, and you need to set up the rocket's flight so that it will work correctly first.  In much the same way that in order to dock with another vessel, you have to rendezvous first, so, too, do you need to get the rocket on a flight path that will most benefit from prograde hold before you activate prograde hold.

In your case, the fact that you had only pitched over by ten degrees suggests to me that you still had too much thrust in the vertical direction, which means that you needed to turn a few more degrees first.  Most of my rockets work best when I pitch between three and five degrees from vertical before taking my hands off of the controls, but some high-thrust models need as many as ten degrees of pitch.  That's not to dismiss @JoeSchmuckatelli's approach of turning hard over by fifteen degrees right away, but I tend to prefer a lighter touch.  Remember that in rocketry, there are two ways to reduce thrust in a given direction: you can reduce throttle, or you can point it in a different direction.  If you're using solid rocket boosters for initial launch, then reducing thrust in-flight is not an option--though you can limit it in the Vehicle Assembly Building.  Of course, that also reduces your acceleration in the horizontal direction, too, and that increases inefficiencies and losses due to fighting gravity--you usually don't want that.

It's also the case that prograde hold's total contribution is to help you to avoid unpleasant surprises and to assist with more difficult payloads; ideally, the rocket is designed in a way that it will fly itself to orbit whether or not you use prograde hold.  Occasionally, someone in the Challenges forum posts a contest to design completely hands-free rockets:  by that I mean a rocket that is designed such that you can press space to launch it, get a cup of tea, and come back to find your rocket comfortably in a stable, circular orbit.

Remember that prograde hold is not necessarily always available.  The various holds and locks are tied to different levels of SAS:  for Pilot-type Kerbals, it's linked to their experience, and for probe cores, the level is a fixed part of the design.  Prograde/Retrograde hold is a level 1 ability, so all probe cores with level 1 SAS and higher have it (that means that the RoveMate, QBE, OKTO, and Stayputnik cores are the ones that do not have it--the HECS is the first that does have it).

[AHHans]

21 hours ago, KrisKelvin said:

Although I just tried that and it doesn't get you into orbit! I was still only pitched over about 10 degrees at 100km altitude!

As others already said: you first need to pitch over manually (and then let the prograde come down, as explained in my other post) before "locking to prograde".

Also the optimal time and amount to pitch depends on the rocket. With this rather high TWR rocket(*) you need to pitch over more aggressively (than my usual rockets), so pitching 10 deg when you reach 50 m/s is O.K. for this rocket. I also want to encourage you to try out different ascent strategies (pitching sooner or later, pitching more or less, throttleing down or not, etc.) and see how well they work. And feel free to post another video. 

(*) The one from you video without the SRBs.

[KrisKelvin]

21 hours ago, JoeSchmuckatelli said:

The really nice thing - and you know you're doing it correctly, is that you end up with a really long arc; such that when your apoapsis is 75 k or so, the end of your arc is often 1/4 or more of the whole circumference of Kerbin.  That makes for a long coast up to apoapsis which lets you have the time to set up a maneuver node to circularize.

What's a maneuver node? Is this some kind of aid I should know about? When I am trying to create an orbit, I just go close to the apoapsis and then line myself up prograde and then burn until I see the orbit come out of the planet surface on the other side. Ain't that right?

[AHHans]

19 minutes ago, KrisKelvin said:

What's a maneuver node?

If you play career then you need to upgrade the tracking station and mission control to be able to place maneuver nodes. (In science and sandbox modes they are available from the start.) If you have them activated, then you can clock on your orbit in map view and place a maneuver node there, then you can modify that node - e.g. pull out the prograde marker in order to plan a maneuver in which you accelerate prograde - and it will show you your predicted orbit after performing that maneuver. It will also show a blue marker on the navball that shows in which direction you need to accelerate for that maneuver and it show next to the navball how much you need to accelerate for that maneuver and when that maneuver is.

19 minutes ago, KrisKelvin said:

Ain't that right?

That's fine. Using a maneuver node "only" makes it more precise. (When done correctly.)

[KrisKelvin]

26 minutes ago, AHHans said:

If you play career then you need to upgrade the tracking station and mission control to be able to place maneuver nodes. (In science and sandbox modes they are available from the start.) If you have them activated, then you can clock on your orbit in map view and place a maneuver node there, then you can modify that node - e.g. pull out the prograde marker in order to plan a maneuver in which you accelerate prograde - and it will show you your predicted orbit after performing that maneuver. It will also show a blue marker on the navball that shows in which direction you need to accelerate for that maneuver and it show next to the navball how much you need to accelerate for that maneuver and when that maneuver is.

That's fine. Using a maneuver node "only" makes it more precise. (When done correctly.)

err... ok. I think I understand. So like an autopilot then? Kind of

[AHHans]

1 hour ago, KrisKelvin said:

err... ok. I think I understand. So like an autopilot then? Kind of

No, not autopilot, it doesn't pilot the rocket for you.

It is a planning tool. I allows you to plan a maneuver and shows you where this maneuver will lead you. (You can also add more maneuver nodes to the predicted orbit/path so that you can plan a complex journey.) And it helps you to perform that maneuver, by showing you where you need to point the rocket and how much to accelerate.

[Zhetaan]

19 minutes ago, AHHans said:

It is a planning tool. I allows you to plan a maneuver and shows you where this maneuver will lead you. (You can also add more maneuver nodes to the predicted orbit/path so that you can plan a complex journey.) And it helps you to perform that maneuver, by showing you where you need to point the rocket and how much to accelerate.

Exactly this, but put another way, it's like drawing a line on a map to show your intended route.

... Well, actually, it isn't like that; it's exactly that, since it's done in Map View.

You're not obligated to follow that route (and without an autopilot mod, nothing will fly that route for you), but it can help you decide both where you want to go and how you might try to get there.  Aside from the replies here, if you want to learn how to get the most out of manoeuvre nodes, then there are literally dozens of tutorials about them, including the ones in KSPedia (pages 21, 22, and 33-35).  Nodes are a fundamental tool in KSP.  They aren't required--you can plan an interplanetary mission without them, and many people have done so (especially in the early days)--but they are extraordinarily helpful.

[JoeSchmuckatelli]

3 hours ago, KrisKelvin said:

What's a maneuver node? Is this some kind of aid I should know about? When I am trying to create an orbit, I just go close to the apoapsis and then line myself up prograde and then burn until I see the orbit come out of the planet surface on the other side. Ain't that right?

I watched you do that in your video - and could not criticize it, because it worked = you got an orbit.  There's lots of players better than I who pilot the whole way and get great results.

I'm a duffer.  I honestly barely understand what is going on behind the scenes, and am not at all afraid to use the tools at my disposal... like maneuver nodes.  Frankly, I could not reach the Mun or Minimus without using them.

As AHHans wrote: when you upgrade tracking station you get maneuver nodes.  The way you use them is to go to map mode, and click somewhere on your flight arc.  In the case I've been describing, that place should be at or adjacent to your apoapsis.  you will get a message that says something like Warp Here or Create Maneuver (I'm not in-game, so bear with the last).  Choose to create the maneuver.  When that happens, you get a circle with all of the directions / pips you see on the navball.  Presuming you know what they mean, you can LMB on the Prograde node and drag it.  Doing so drags a dotted 'prospective flight path' usually a brownish / orangish color that will eventually show a periapsis.  When AP and Pe are about even - you have a circular orbit... and to the right of the navball you get a T minus number (that counts down / up) and a burn time indicator.  Refer back to what I've written previously and it should all make sense.

Sorry for presuming you knew what I was describing.  I use them so ubiquitously that I assumed everyone did too!

 

EDIT: two more things;

1   --  if / when you click anywhere off the node you created, it will turn into a star shaped doohickey on your flight path - and it can be hard to see.  The green time to node info remains next to the navball, even if you can't see it.  You can click it again to open it, or RMB to delete it.  You can also grab the central circle to drag it around your flight path to see where you end up / what kind of encounters you get.  So, lets say that you want to get to Minmus.  You guestimate some place on your flight path where Minmus is barely visible on the right side of your screen, drag prograde until the projected flight path gets to the orbit of Minmus *your Ap marker... then if you don't see a Pe next to Minmus, you grab the central circle and slide it around until you do get a Minmus Pe.  You can then fiddle with everything to get closer (like even hit the moon).  Oh, and before you do this (if going to Minmus or elsewhere) you should zero out your Ascending / Descending nodes (google how to do this) before (BEFORE) trying to get a Minmus encounter.

2.  Once you've completed your burn, go back and delete the node you just used.  Otherwise it will just annoy you / mess with future maneuvers (because KSP allows you to plan multiple nodes).  You may have to hold the click for a bit to get it to disappear (fast clicks give a 'Can't be deleted' message for some reason)

Edited May 28, 2020 by JoeSchmuckatelli

[JoeSchmuckatelli]

9 hours ago, KrisKelvin said:

err... ok. I think I understand. So like an autopilot then? Kind of

Not really an autopilot as an auto-planner.

So - FWIW (For What It's Worth), I'm new to the whole 'hold prograde' thing.  But I just had a launch I think you would be interested in... if only I could have recorded it.  

I've got a payload every bit as big as my main rocket.  Not mass wise, but length wise.  A true Kerbal-disaster of a ship.  I'm using my usual rocket with no changes to the lower stages.

I get in a hurry as I launch the thing, push the navball into a really agro, almost 20 degree turn starting at 34 m/s and then hit 'Hold Prograde' once the prograde marker catches up to my flight indicator pip.  This happens because I'm not really paying attention; I'm trying to get the launch done before I had to sign off.  When I see the drag lines I backed way off on the liquid fuel rocket to save fuel and let the SRBs burn.  Took me a while, but I finally realize that I'm in an absurdly low angle of attack from what I usually do.  Like I'm already 45 degrees and not even 19k.  Starting to wonder if my apoapsis is even going to get out of the atmosphere.  Thinking of reverting, because I'm starting to realize I totally goofed up.

But.

My ship isn't tumbling.

And it's going screamingly fast in the mid atmosphere.

so...

I decide to pump up the liquid fuel engine a bit earlier than usual to try to drive my Ap up while the ship is pointed up.  At this point, I'm literally 70 degrees off the vertical, and still in the atmosphere.

Turned out fine.

Flattest arc to 75k I've ever taken.  Long coast to Ap and the maneuver node to circularize took much less time than usual.

IOW - you can in 1.-09 (or whatever version is current) take some really agro angles off the launchpad to get to orbit!

 

[AHHans]

2 hours ago, JoeSchmuckatelli said:

Like I'm already 45 degrees and not even 19k.

Errr.... O.K.

Here are my rules of thumb for when I launch "normal" rockets:

• pitch 5 - 10 deg when
• aim for 45 deg pitch at 10 km altitude (Yes, that's why I was confused about your statement.)
• keep TWR below 2 (throttle down if needed), in particular in the lower parts of the atmosphere
• keep time to apoapsis either increasing or at 1 - 1.5 min
• if I come in too low then I can
  • throttle up (if not yet at max)
  • pitch higher than prograde, switching SAS from prograde-hold to stability-assist for some time might already do it
• if I come in too high then I can:
  • throttle down (preferred if not at the very start of the ascent)
  • pitch lower than prograde: needs to be done manually, I usually only do this if my initial pitch over was too small

A high drag / low TWR rocket need a higher arc than a low drag / high TWR rocket:

• when in doubt then drag is more relevant than TWR
• if it looks like a "real" rocket then it is low drag (e.g. if the payload is in a fairing and that fairing doesn't look like a pancake on a stick)
• high drag are craft that have many draggy parts outside a fairing. In particular uncovered connection nodes.
• Drag examples: this is a low drag rocket (although IIRC it has low-ish TWR); this is still a low-ish drag rocket; this and this are high drag rockets, they need a high ascent to get out of the thick part of the atmosphere quickly - independent of TWR.
• low TWR is when much of the ascent is done with a TWR smaller than 1.5
• high TWR is when the rocket starts out a > 1.5 and/or goes above a TWR of 2
• I usually have a TWR of 1.3 as the minimum of the first stage, TWR of a little below 1 is O.K. for later ascent stages (e.g. when I dump the SRBs), TWR significantly below 1 only for the final circularization, for deep-space maneuvering I prefer a TWR > 0.2 (otherwise the maneuvers get too boring)

 

[KrisKelvin]

11 hours ago, JoeSchmuckatelli said:

As AHHans wrote: when you upgrade tracking station you get maneuver nodes. 

Ok, just to clarify something... I think what you are referring to here is a game mode I have not tried yet. I am only using sandbox mode (I assume the other modes are if you want to make this more of a game mimicking someone's 'career' as an astronaut - so I haven't tried them). I could be wrong about that, but I only want to fly spaceships so I assumed the sandbox mode was the only thing that would interest me. But please feel free to set me straight on modes!

And thanks again to everyone - I have never been on such a helpful forum!

[Zhetaan]

4 hours ago, KrisKelvin said:

(I assume the other modes are if you want to make this more of a game mimicking someone's 'career' as an astronaut - so I haven't tried them)

Not quite, though I can see why you would think that.  Career mode is not a role-playing sort of experience, but it does have additional difficulty elements.  In Career mode, you begin with only a few parts and with facilities that are incapable of supporting rockets over a very limited size, mass, and number of components.  There are also certain activities that you cannot do, such as EVAs and taking surface samples, until you upgrade certain facilities.  In order to upgrade your capabilities and facilities, you need to complete missions (from Mission Control, which in Sandbox mode is closed) for Funds and you need to complete science experiments for Science points.  Funds are money that you use to pay for your rockets and for facility upgrades (and to hire new astronauts from the Astronaut complex), and Science points are used to unlock new technologies at the Research & Development complex.  There is also a third currency called Reputation that influences the value of the contracts that you are offered.

As such, Career mode creates a balancing act where you need to (at least in the beginning) compare the cost of your rocket and launch to the expected reward from any contracts that you may be trying to complete with that rocket, and still manage your designs against the constraints of the bottom-tier facilities.

Science mode is somewhat between Sandbox and Career modes; in it, the rocket parts are locked and you need to obtain Science points (through science experiments) to research and unlock them, but the rockets don't cost anything and the facilities are fully equipped.  Thus, there is progression through the tech tree and challenges that arise from needing to complete your goals while using a limited pool of parts, but you're not also managing the money to build things.

One of the features of Science mode is that you have to progress through technologies from a low-tech beginning, so you're not faced with a confusing abundance of different rocket parts at the start of the game; needing to unlock the tech gives a sense of progression from less capable rockets to more capable rockets, in addition to increased mission complexity.

[JoeSchmuckatelli]

6 hours ago, KrisKelvin said:

Ok, just to clarify something... I think what you are referring to here is a game mode I have not tried yet. I am only using sandbox mode (I assume the other modes are if you want to make this more of a game mimicking someone's 'career' as an astronaut - so I haven't tried them)... 

The advantage, as I see it, to playing Career is that you start out with a limited but totally workable set of parts - which really helps with the learning progression.  I tried Sandbox when I first got started and found it to be too much too soon.  Career is also kind of fun b/c you do get missions that maybe you otherwise wouldn't do in SB but which forces you to learn something new at a reasonable pace. 

If you are in SB, however everything should be unlocked - so you should have maneuver nodes available. 

7 hours ago, AHHans said:

Errr.... O.K.

Here are my rules of thumb for when I launch "normal" rockets:

• pitch 5 - 10 deg when
• aim for 45 deg pitch at 10 km altitude (Yes, that's why I was confused about your statement.)
• keep TWR below 2 (throttle down if needed), in particular in the lower parts of the atmosphere
• keep time to apoapsis either increasing or at 1 - 1.5 min
• if I come in too low then I can
  • throttle up (if not yet at max)
  • pitch higher than prograde, switching SAS from prograde-hold to stability-assist for some time might already do it
• if I come in too high then I can:
  • throttle down (preferred if not at the very start of the ascent)
  • pitch lower than prograde: needs to be done manually, I usually only do this if my initial pitch over was too small

A high drag / low TWR rocket need a higher arc than a low drag / high TWR rocket:

• when in doubt then drag is more relevant than TWR
• if it looks like a "real" rocket then it is low drag (e.g. if the payload is in a fairing and that fairing doesn't look like a pancake on a stick)
• high drag are craft that have many draggy parts outside a fairing. In particular uncovered connection nodes.
• Drag examples: this is a low drag rocket (although IIRC it has low-ish TWR); this is still a low-ish drag rocket; this and this are high drag rockets, they need a high ascent to get out of the thick part of the atmosphere quickly - independent of TWR.
• low TWR is when much of the ascent is done with a TWR smaller than 1.5
• high TWR is when the rocket starts out a > 1.5 and/or goes above a TWR of 2
• I usually have a TWR of 1.3 as the minimum of the first stage, TWR of a little below 1 is O.K. for later ascent stages (e.g. when I dump the SRBs), TWR significantly below 1 only for the final circularization, for deep-space maneuvering I prefer a TWR > 0.2 (otherwise the maneuvers get too boring)

 

I'm laughing as I read this - b/c clearly for you, launching to orbit is a deliberate, planned and understood thing. 

Sadly, I'm not there yet.  I'm still in the 'slap a bunch of stuff on that looks like it should work and try what didn't fail last time' mode.  I really have no idea what altitude it was that I was 45ish degrees - I guessed - but I know that it was way lower than usual.  I did learn that I'm also not nearly as efficient as I thought - because clearly the lower attack worked! 

Anyway - thanks for the long explanationatory post! Through this kind of stuff I can move towards being more deliberate and less Jebby in my approach! 

So +are you tracking the twr number after launch?  I haven't figured out how to use the info provided by the new lower left box that lets us switch between maneuver and docking etc.  Is that where you are looking? 

 

EDIT:  Here's my ship - https://imgur.com/a/gr3OeRJ  (* for some reason I can't insert the image)

Edited May 29, 2020 by JoeSchmuckatelli

[AHHans]

53 minutes ago, JoeSchmuckatelli said:

I'm laughing as I read this - b/c clearly for you, launching to orbit is a deliberate, planned and understood thing. 

"deliberate"? Well, yes: I didn't hit <SPACE> by accident. But after that it's every Kerbal for their own!
"planned"? Hmm... Does "I always do it that way, and most of the time it worked" count as planning?
"understood"? Hu?!? Whut's that?

The only real numbers that I actually look out for are the 45 deg at 10 km and the 1 min time-to-apoapsis. The rest is most following my gut feelings. (O.K. and competing in things like the launch profile challenge that I mentioned earlier, taught me a bit why some things work and others don't.) My post was really trying to put what I just usually do without thinking too much about it into words.

1 hour ago, JoeSchmuckatelli said:

I did learn that I'm also not nearly as efficient as I thought - because clearly the lower attack worked! 

I think I also usually launch steeper (getting too high too fast) than optimal. But launching too steep "only" costs more fuel, while launching too shallow can cause the mission to fail - due to overheating, because the rocket flips out, or because you do have too much drag and run out of fuel. And what the challenge above showed me is that you can go quite a bit too steep before it costs you significant amounts of fuel.

1 hour ago, JoeSchmuckatelli said:

Through this kind of stuff I can move towards being more deliberate and less Jebby in my approach! 

You can also do what I did: build a rocket that can only just so get into orbit and then launch it again and again until you get it into orbit more often than not. (My first design for a tourist bus was like that.)

1 hour ago, JoeSchmuckatelli said:

So +are you tracking the twr number after launch?

Most of my rockets don't have high enough TWR that it is useful to monitor the TWR. (If you have high TWR then you can usually save money by mounting a smaller engine until you have a low TWR rocket.) But recently I follow the "just slap an oversized booster on that stuff" philosophy of rocket engineering more often, and with those it is indeed useful to monitor the TWR during launch. (It is really embarrassing to run out of fuel on your launch after adding an oversized booster to your payload because you didn't pay attention to what your rocket is doing.)

1 hour ago, JoeSchmuckatelli said:

(* for some reason I can't insert the image)

You need to add the URL of the image file itself, not of the imgur page for that image or the URL for the album. With imgur you need to get the URL for the image itself and then add ".png" (or ".jpg" if you like) to the URL that imgur gives you. So inserting "https://i.imgur.com/jbhy7Nd.png" works. (You can also right-click and select "view image" in your browser, and then copy&paste the URL from your browser.)

[JoeSchmuckatelli]

Grin

 

Okay - so if you look at the image I linked: the rocket with Mainsail and two Polluxes has a TWR (in the VAB) of only 1.6.  That seems okay to me.  

So - to understand what you wrote above - are you seeing TWR numbers somewhere while in flight?  And do they change?  Is that how you're deciding whether to throttle back or up?

[AHHans]

17 minutes ago, JoeSchmuckatelli said:

So - to understand what you wrote above - are you seeing TWR numbers somewhere while in flight?  And do they change?  Is that how you're deciding whether to throttle back or up?

Yes, If you expand the staging view during flight then it will show you the same information like in the editor (only on the left screen not the right). This information is continuously updated during flight (i.e. as you burn fuel and get to thinner atmosphere).

23 minutes ago, JoeSchmuckatelli said:

Okay - so if you look at the image I linked: the rocket with Mainsail and two Polluxes has a TWR (in the VAB) of only 1.6.  That seems okay to me.  

Yes. It also doesn't look totally overpowered to me. From the performance values it looks like something I would build. (Except that I like to use the Twin-Boar and not the Mainsai / Skipper, so I probably would use that instead of the Mainsail, kick out the Skipper stage altogether, but add more fuel to the Wolfhound stage for final ascent & circularization. And of course your payload is totally wrong ... errr ... not the way I do things. But other than that... O.K. Don't have parts sticking out of the fairing, that just looks odd!)

[JoeSchmuckatelli]

1 hour ago, AHHans said:

Yes, If you expand the staging view during flight then it will show you the same information like in the editor (only on the left screen not the right). This information is continuously updated during flight (i.e. as you burn fuel and get to thinner atmosphere).

Yes. It also doesn't look totally overpowered to me. From the performance values it looks like something I would build. (Except that I like to use the Twin-Boar and not the Mainsai / Skipper, so I probably would use that instead of the Mainsail, kick out the Skipper stage altogether, but add more fuel to the Wolfhound stage for final ascent & circularization. And of course your payload is totally wrong ... errr ... not the way I do things. But other than that... O.K. Don't have parts sticking out of the fairing, that just looks odd!)

LOL @ the faring.  I deleted it to show the payload and then slapped it back together.  

(Now that I have pretended to be a rational player... Yes I have built wider stuff and cheated a faring through it... But let's not tell anyone else!) 

I'm guessing the 'proper way' to have done this mission was with two launches. This bizarre payload is the result of extreme laziness. 

Mind you, I got to fly the mission 3 times before I stuck the landing... But we won't mention that either. 

I looked at the Twin Boar but somehow decided that the Mainsail was a better option.  Care to correct my thinking? 

[AHHans]

8 minutes ago, JoeSchmuckatelli said:

I'm guessing the 'proper way' to have done this mission was with two launches. This bizarre payload is the result of extreme laziness. 

No, there is no such thing as a "proper" way! And you payload isn't more bizarre than the stuff that I routinely launch. (Have a look at my KerbalX collection. These are the ones that I cleaned up for public presentation.) It is just that your payload is different than what I do. Not better or worse, not more or less bizarre, just different. (But then again, my way is the only correct way. So there!)

12 minutes ago, JoeSchmuckatelli said:

I looked at the Twin Boar but somehow decided that the Mainsail was a better option.  Care to correct my thinking? 

I personally like the Twin Boar better. Except my personal preferences I don't see much of a difference. (And it has totally nothing to do with the procurement manager of AHTech Industries being the sister in law of a sales manager at Kerbodyne!)

[Zhetaan]

2 hours ago, JoeSchmuckatelli said:

I looked at the Twin Boar but somehow decided that the Mainsail was a better option.  Care to correct my thinking? 

It depends on the use.  The Mainsail is somewhat more efficient, but the Twin Boar is higher thrust, which means that for borderline cases, the Twin Boar can loft a somewhat larger payload.  The Twin Boar costs less than a Mainsail+Jumbo Tank combination (17,000 versus 18,750 Funds), so that could be be worth considering.

There's a comparison from several years ago that might help with this.  It also includes notes on building launchers and the kinds of design parameters you'll probably want to consider, such as the best ranges for thrust-to-weight.

It doesn't include anything about launch profile, though, but on the other hand, if you follow the guide and can build a rocket that is absolutely capable of reaching orbit, then you know that any problems subsequent to that are the result of pilot error and pilot error alone.  That can be extremely helpful, because I know that it can drive one to total exasperation to try, and try, and try to reach orbit, only to find out that the rocket was never capable of getting there in the first place.

 

Edited May 29, 2020 by Zhetaan

[JoeSchmuckatelli]

4 hours ago, Zhetaan said:

It depends on the use.  The Mainsail is somewhat more efficient, but the Twin Boar is higher thrust, which means that for borderline cases, the Twin Boar can loft a somewhat larger payload.  The Twin Boar costs less than a Mainsail+Jumbo Tank combination (17,000 versus 18,750 Funds), so that could be be worth considering.

There's a comparison from several years ago that might help with this.  It also includes notes on building launchers and the kinds of design parameters you'll probably want to consider, such as the best ranges for thrust-to-weight.

It doesn't include anything about launch profile, though, but on the other hand, if you follow the guide and can build a rocket that is absolutely capable of reaching orbit, then you know that any problems subsequent to that are the result of pilot error and pilot error alone.  That can be extremely helpful, because I know that it can drive one to total exasperation to try, and try, and try to reach orbit, only to find out that the rocket was never capable of getting there in the first place.

 

Awesome read - thanks for the link! 

 

Any idea where the '9.81' comes from? 

" Second stage target thrust = 54 x 9.81 x 1.2 = 636 kN (vacuum)" 

 

 

EDIT:  So I tried out a lifter build based on what I read - with mixed results.  I followed the simple version: 1x Payload fuel mass for Stage 2 and 2x Payload fuel mass for Stage 1.  Stage 2 had a Wolfhound, while I used a Twin Boar for Stage 1 (45 ton payload).

First launch... did not want to cooperate.  Flew fine, but laid over way too much way too soon.  No orbit.

Second launch... got higher, but not enough.  I added a pair of Polluxes to give it a bit more off the pad oomph.  High enough Ap but not enough speed to orbit.

Third launch... a pair of Clydesdales to the rescue.  Was very interesting for me: there was no 'coast to Ap' time at all.  Full first stage burn (although I did enjoy some throttle down time) and once the second kicked in, I burned continuously on prograde hold to orbit.  My very first orbit in a long time without using a Maneuver node for circ.  Ended up with abt 1/2 the fuel set aside for the second stage still in the tank - so I probably gooned up the gravity turn... but frankly I'm not complaining!

Edited May 30, 2020 by JoeSchmuckatelli

[OhioBob]

4 hours ago, JoeSchmuckatelli said:

Any idea where the '9.81' comes from? 

" Second stage target thrust = 54 x 9.81 x 1.2 = 636 kN (vacuum)" 

That's the standard acceleration of gravity, actually 9.80665 m/s².  It's used as a conversion factor to convert kilograms (mass) to Newtons (force).

[JoeSchmuckatelli]

1 hour ago, OhioBob said:

That's the standard acceleration of gravity, actually 9.80665 m/s².  It's used as a conversion factor to convert kilograms (mass) to Newtons (force).

I wondered about that.  Sadly I was too unfocused back in college to take the courses about stuff that interests me now.

[KrisKelvin]

11 hours ago, JoeSchmuckatelli said:

Awesome read - thanks for the link! 

Hey Joe! This is my question thread remember! 

;-)

Jus kidding

[JoeSchmuckatelli]

3 hours ago, KrisKelvin said:

Hey Joe! This is my question thread remember! 

;-)

Jus kidding

Grin - I have hijacked it for shore! 

/internet