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Schmelge

Delta V and Boosters

Question

Hey everyone.

So I'm struggling a bit both with getting satellites to orbit and to make airplanes that can fly high altitudes.

Last night I was googling for some tips and tricks and I came over a thread with someone posting a picture of a plane he made.

https://m.imgur.com/Q7J5cyL

 

As you can see in the pic his thrust limit is 36 and he woops out a smashing 23.4 k delta V?!?!

 

I tried to make roughly the same model but I get nowhere close to that! 

Thrustlimit set to around 1 and I get something like est 8 min burn. Ofcourse that thrust is so small even a light aircraft would never lift.

 

How is this possible? How can he have a twr if 1.02 and an estimated burn of 14 hours??

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7 minutes ago, Schmelge said:

i cant reach the ice shelves :(

That's just like... 1/5th of the way around the planet. Should be easily within the capability of even basic jets. Looks like you still have a lot to learn about building and flying :wink: But don't let that discourage you. KSP is just the kind of game where you can play for months and still learn more.

First, decide if you want to fly subsonic or supersonic. All of the engines in stock KSP are capable of supercruise - steady flight at more than mach 1 - but the early models (Juno and Wheesley) have some issues with breaking the sound barrier, which is quite literally a wall of extremely high drag. The reason is that they cannot fly very high without losing thrust, so the drag hits them extra hard.

For building planes, flying subsonic means: lots of wingspan and area, and make them straight (or only mildly swept). "Not enough wing" is a classic beginner mistake when it comes to planes. If you plane isn't taking off at something like 50-60 m/s, you can use more wing. (But keep in mind that poorly positioned rear landing gear can keep your plane from pitching up on the runway, which may give you the wrong impression in regards of takeoff speed.) In flight, aim for around 275-300 m/s cruise speed.

If you have Panthers or better, you should definitely be building a supersonic plane. That means: narrow but long shape, with strongly swept wings, or better yet, delta wings. Rule of the thumb: the faster you plan on going, the more your plane should resemble the shape of a sleek arrowhead. You don't need to get the best subsonic performance, such as low take-off speeds; that's just a nice bonus if you can manage it. What matters is how the plane performs beyond the sound barrier. 700 m/s is a good target speed for Panthers without afterburners; but don't be shy, and toggle them on, because they not only add thrust, but also allow you to fly higher without losing thrust. 900 m/s is a good speed for afterburning Panthers.

The trick here is to find a comfortable cruising altitude for your specific plane. The higher you go, the less drag there is, but also, the more thrust your engines lose. Additionally, if you don't have enough wing, you need to fly with your nose pitched up just to maintain lift, which creates extra drag and nullifies the advantage of flying that high in the first place. Climb to a good starter altitude and throttle your engines to the point where you can maintain your target speed in level flight. With Junos, try 8 km; with Wheesleys, 10km; with dry Panthers, 11 km; and with afterburning Panthers, 14 km. Then try going higher or going lower. Does this help you go faster at the same engine throttle? If yes, adjust your throttle to again match your target speed in level flight, and then continue looking for a better altitude. Just remember that gaining altitude makes you go slower, and losing it makes you go faster; always make sure to be as levelled out as you can before comparing performance.

After that, it's all just a question of carrying enough fuel and having enough patience to go the distance.

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19 minutes ago, Schmelge said:

How is this possible? How can he have a twr if 1.02 and an estimated burn of 14 hours??

For starters, you're reading the screenshot wrong. :P 

The plane in question carries two solid boosters in stage two. They are listed as providing 929 m/s dV across 43.7 seconds of burntime. The likely use case is to have a boost stage to achieve an altitude that a jet engine cannot reach, in order to - for example - fulfill a contract goal.

The first stage, with the huge dV reading, uses an airbreathing jet engine. Which one, I have no idea; there currently are no jet engines in stock KSP that put out 115 kN nominal thrust. So either the engine is from a mod, or that screenshot is very old. I'm tempted to go with the former, because while I don't remember all the old jet engine stats across the versions, 19,200s specific impulse is absurdly high. No stock jet engine currently goes higher than 12,600.

The dV reading is so large, and the burn time so long, because of that huge 19,200s specific impulse.

 

Edited by Streetwind
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Aaah well that explains quite alot xD

Would sure be nice to have that jet engine though :P i cant reach the ice shelves :(

 

Thanks for the answer m8 :)

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If anyone reads this thread and happen to know of a mod that provide such a nice engine please reply :D

Edited by Schmelge

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23 minutes ago, Streetwind said:

That's just like... 1/5th of the way around the planet. Should be easily within the capability of even basic jets. Looks like you still have a lot to learn about building and flying :wink: 

Haha yeah but the distance feels like I'm trying to fly to the sun or something and yes I do have ALOT to learn :D

I printscreened my 2 first airplanes and also my list of mods. Maybe if you have the time you could check at least the two aircrafts and tell me what is wrong with them? They fly very nice, super stable, but I don't get the distance.

The first edition only flies around 13 min, the barrels that make up the middle of the plane are structural, the junos can't lift if they contain fuel and the second one I adjusted the power of the engines "rattlers" so they can fly around 40 min, if I leave them on 100% they have a twr of 1.20 and can fly around 33 min, the middle of the plain is filled with fuel.

 

In my modlist you will find a couple that most likely will make it alot harder for me to advance, however I do like that I have to take the baby steps before I get good parts. Although.. It does make it extremely hard when I can't even reach the  ice shelves.

 

First and second plane:

Airplanes

Modlist:

My mods

Thanks so muc for the answers man, it's really appriciated!

 

 

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Actually, it is possible to circumnavigate Kerbin even with a Wheesley jet engine.  I did it flying at mach 0.9 @ 6km in just under 4 hours to complete the Kerbin Circumnavigation challenge.  If I recall correctly, the Wheesley only has an Isp of 10,500s.

Album a/bPyJ8 will appear when post is submitted

Check out the Kerbin Circumnavigation challenge thread.

 

Edited by Skystorm
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23 minutes ago, Schmelge said:

First and second plane:

Airplanes

Yeah, I think both of those qualify for "not enough wing".  :P 

You also have too much drag. On both planes, the front fairing bulging around the battery is a big offender. I'd toss the fairing and everything in it completely, switch to the regular mk1 cockpit instead of the inline one, mount the battery inline instead, and put a single radial parachute on top of the plane. Additionally, the second plane has too many air intakes. One equally sized intake per engine is enough in all but the most extreme cases, and your small jets already have intakes on them.

I can try to whip something up when I get home, but I'm not even that good with planes. Many other forum users will wipe the floor with my creations. Threads with plane-related challenges like the one linked above are great sources for design inspiration (though they may be using parts you don't have access to yet).

Edited by Streetwind
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2 hours ago, Streetwind said:

The first stage, with the huge dV reading, uses an airbreathing jet engine. Which one, I have no idea; there currently are no jet engines in stock KSP that put out 115 kN nominal thrust. So either the engine is from a mod, or that screenshot is very old. I'm tempted to go with the former, because while I don't remember all the old jet engine stats across the versions, 19,200s specific impulse is absurdly high. No stock jet engine currently goes higher than 12,600.

The dV reading is so large, and the burn time so long, because of that huge 19,200s specific impulse.

 

Check the KER version, 1.0.16.5 was released at the start of May 2015, so just after 1.0 was released.  Old aero, old parts, I think.

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37 minutes ago, Streetwind said:

Yeah, I think both of those qualify for "not enough wing".  :P 

You also have too much drag. On both planes, the front fairing bulging around the battery is a big offender. I'd toss the fairing and everything in it completely, switch to the regular mk1 cockpit instead of the inline one, mount the battery inline instead, and put a single radial parachute on top of the plane. Additionally, the second plane has too many air intakes. One equally sized intake per engine is enough in all but the most extreme cases, and your small jets already have intakes on them.

I can try to whip something up when I get home, but I'm not even that good with planes. Many other forum users will wipe the floor with my creations. Threads with plane-related challenges like the one linked above are great sources for design inspiration (though they may be using parts you don't have access to yet).

Haha aight! :D

Looking forward to see what you can come up with :D

 

In addition to this comment, I have to appologize for something quite embarrassing.. I didn't know that I already researched the Wheesly engine -.-' 

When I noticed that I had this engine and mounted it on a tank, I saw that I can now fly for 57 minutes. If I tweak the engines I can make it to around 1 hour 29 minutes... That should definitely be enough to reach the ice shelf :D
However, what throws me off abit, something I do not understand, is the airintake. The Wheesly says it needs 29.6 / s per engine but the circular intake I have mounted only gives 2.0 per engine, despite this, the engine work flawlessly and and quick test showed I got up close to 600 m/s

However I still would love to see some super simple basic airplanes, preferably if you could show me how far you can get on a juno and a rattler :) I still havn't researched far enough to have the mk1 cockpit so what you see is what I have :P

 

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1 hour ago, Schmelge said:

 if you could show me how far you can get on a juno

If distance is your problem, either bring more fuel or burn less. There is nothing stopping you from adding another small fuel tank ( or more)  in-line with your existing juno jet engines.

Intake, tank, tank, engine.

 

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EvtEyMM.jpg

sFJzulq.jpg

This is what I'm using in my current caveman career. It can reach anywhere on Kerbin.

Best,
-Slashy

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1 hour ago, GoSlash27 said:

EvtEyMM.jpg

sFJzulq.jpg

This is what I'm using in my current caveman career. It can reach anywhere on Kerbin.

Best,
-Slashy

Nice! What engine do you use?

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basic_jets.jpg

Here are a couple of mine.

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14 minutes ago, Schmelge said:

Nice! What engine do you use?

Schmelge,

 Just the Wheesley and a couple Mk1 tanks.

 Are you sure you don't have the Mk1 cockpit? You were supposed to unlock that with basic aviation.

Best,
-Slashy

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8 minutes ago, GoSlash27 said:

Schmelge,

 Just the Wheesley and a couple Mk1 tanks.

 Are you sure you don't have the Mk1 cockpit? You were supposed to unlock that with basic aviation.

Best,
-Slashy

Yes m8 am sure, i will get that in the next branch that I can unlock, however I have insufficient funds to do so right now :D

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Schmelge,

 Well, you'll probably be just fine with the fairing for a nose and the inline cockpit. If it were me, I wouldn't bother with the big battery. The plane doesn't really use much electricity and will still fly even with a dead battery.
 For advice... Don't be afraid to give it wings. You're going to cruise long distance and land in rough terrain and big wings are a good solution for both of those situations.
 Best,
-Slashy

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2 hours ago, GoSlash27 said:

This is what I'm using in my current caveman career. It can reach anywhere on Kerbin.

Best,
-Slashy

@GoSlash27,

Any particular reason you play KSP in a windowed mode?

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10 minutes ago, GoSlash27 said:

Schmelge,

 Well, you'll probably be just fine with the fairing for a nose and the inline cockpit. If it were me, I wouldn't bother with the big battery. The plane doesn't really use much electricity and will still fly even with a dead battery.
 For advice... Don't be afraid to give it wings. You're going to cruise long distance and land in rough terrain and big wings are a good solution for both of those situations.
 Best,
-Slashy

Thanks for the advice Slashy! Reason I have the battery was that I thought I needed it for my science modules to work. Maybe the cockpit can provide with enough to sustain all tests and sending the results back to KSC without another battery. I'll try it out :) btw, the first plane you posted, is that mk1 cockpit followed by 3 mk1 tanks and a wheesly engine? What is the wingtype you are using? And also, on the wings what kind of "small" planks or mini wings do you put on them? Sorry I don't know what they are called, they make you able to navigate up and down and to the sides :D

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15 minutes ago, Schmelge said:

btw, the first plane you posted, is that mk1 cockpit followed by 3 mk1 tanks and a wheesly engine?

 2 Mk1 tanks and a Science Jr. The engine is a Wheesley fed by 2 XM-G50 radial intakes.
 

 

15 minutes ago, Schmelge said:

What is the wingtype you are using?

The wings are 4 "wing connector B" panels.
 

 

15 minutes ago, Schmelge said:

And also, on the wings what kind of "small" planks or mini wings do you put on them?

The ailerons. They are "Elevon 1" control surfaces. I have them set to respond only to roll. My vertical stab and elevators are "tail fin" control surfaces. The elevators respond only to pitch and the vertical tail doesn't respond to anything at all. I've also disabled the reaction wheel in my cockpit.

Best,
-Slashy

Edited by GoSlash27

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8 minutes ago, GoSlash27 said:

 2 Mk1 tanks and a Science Jr.
 

 

The wings are 4 "wing connector B" panels.
 

 

The ailerons. They are "Elevon 1" control surfaces. I have them set to respond only to roll. My vertical stab and elevators are "tail fin" control surfaces. The elevators respond only to pitch and the vertical tail doesn't respond to anything at all. I've also disabled the reaction wheel in my cockpit.

Best,
-Slashy

Huge thanks for everything m8, can I ask what you have your thrustrate, twr and burntime on? :)

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2 minutes ago, Schmelge said:

Huge thanks for everything m8, can I ask what you have your thrustrate, twr and burntime on? :)

Well, I cruise at full throttle. I'd have to be home to figure out the twr. As for the burntime, I can calculate that. By my math, a Wheesley would go through 4 tonnes of jet fuel in 57 minutes.
 Best,
-Slashy

 

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43 minutes ago, GoSlash27 said:

Well, I cruise at full throttle. I'd have to be home to figure out the twr. As for the burntime, I can calculate that. By my math, a Wheesley would go through 4 tonnes of jet fuel in 57 minutes.
 Best,
-Slashy

 

off by 12 seconds man :D haha impressive :D

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