Those Stupid Airborne Missions

[Corona688]

You know the kind of missions which start filling up your queue after a while:  "Measure temperature 69,000m above Jeb's Outhouse" or what have you.  Bloody unrealistic without ramjets, VTOL and infinite fuel.  Or so they seem so far.  I've tried a number of approaches.

• Setting a pack of small rockets down nearby so I can aim for these high-atmosphere spots with greater precision.  Requires a massive plane or massive rocket and massive luck, and doesn't work.
• Adding rockets to my plane to push it into higher atmospheres.  Doesn't work.  Doomed by weight and center of gravity problems.
• Aiming at these spots from orbit.  The orbit planner isn't accurate enough.  I've never actually *NEEDED* mechjeb before, jeez.

At this point I realized I could get into kerbosynchronous orbits above a spot and descend *STRAIGHT* down and felt clever for about 3 seconds until I realized

a) That only works for spots on the equator

b) Re-entry would wreck you every time

c) Once you leave orbit it gets harder and harder to stay on course

These missions seem to require something like a balloon or dirigible which can loiter for days at a time in the high atmosphere.  I don't know anything in the game like that, nothing capable of lifting a crew pod anyway.  How do you deal with them?

Edited June 16, 2016 by Corona688

[JoeNapalm]

69K is the upper edge of the atmosphere. Basically it's space, with a tiny bit of drag.

Couldn't you just establish a stable orbit above the target location, then edge it down at the appropriate moment?

Either as part of your re-entry, or you have an elliptical orbit and just skim down into the atmo for the readings. You can make as many passes as you need, really, if you have enough of a buffer.

You don't need to be stationary to take a reading. Just bind the instrument to an action group and tap it when you're in the right spot.

-Jn-

[Archgeek]

2 minutes ago, JoeNapalm said:

You don't need to be stationary to take a reading. Just bind the instrument to an action group and tap it when you're in the right spot.

I sense the problem is that at the speed in question, the window in which to do so is exorbitantly tight.

Still, it doesn't take a lot of rocket to get a sounding probe up out of the atmosphere -- I'd say design a probe with antenna, thermometer and battery that gets just above say 71km in a straight-up trajectory (so that it loiters at the right altitude for a bit), put it on a cart in a cargo plane, fly that out to Jeb's Outhouse, launch it straight up, take and transmit the reading, and let the atmosphere scrap the ostensibly-cheap probe.

[moogoob]

I like the idea of balloons. Heck, NASA launches balloons all the time for atmospheric studies. A rocket launched from a balloon would be ideal for these types of mission.

[Snark]

Actually, it's pretty easy-- you just have to be careful with your design, and think small.

I usually don't do a lot of that sort of mission, other than maybe one or two in early career for an infusion of cash and reputation.  However, I've found that it's not too hard to build a small jet + rocket plane that can get pretty much anywhere it needs to.

Make a very small, light plane powered by a couple of Junos, and include a 2-ton tank of LFO with a Terrier.  Emphasis on "small".  You want to keep it as tiny and light as you can:  basically, just a Mk1 cockpit with the 2-tonner and Terrier behind it, a couple of Junos with Mk0 tanks on the sides, and then wings / gear; that's basically it.  If you're going over 5 tons or so, you're too heavy.

The Junos are so fuel-efficient that they can fly you a long distance from KSC with minimal fuel requirement.  When you get to the target site, you're flying at the Junos' operational ceiling, up around 10-12 km, which is high enough that the Terrier gets very close to its vacuum Isp (which is excellent).  So at that point, you just point your nose at the sky and kick the Terrier in the pants.

A Terrier pushing a small plane with 2 tons of propellant packs quite a lot of dV, and can pop your altitude pretty much as high as you like.  (For example, if your total plane mass is 5 tons, a Terrier with 2 tons of propellant will get you over 1700 m/s of dV, plenty enough to get to the top of the atmosphere.)  Loft up to the target altitude, snag the contract, fall back to where the Junos can kick in again; then fly back home.

(Also, moving to Gameplay Questions.)

[Corona688]

I don't have the Terrier engine...  Yet...  but obviously I'll be wanting that next.  Thanks.  This mission may require being willing to throw away most of the plane when I get to the destination

69,000m above jeb's outhouse was a slight exaggeration of "above the flight ceiling of conventional engines but annoying to get to on a suborbital hop".

I have spent a lot, *A LOT* of time trying to get to these places from orbit, more quicksaves than you've got fingers and toes, etc.  I don't think it's practical without something like mechjeb.

Edited June 16, 2016 by Corona688

[Snark]

1 minute ago, Corona688 said:

I don't have the Terrier engine...  Yet...  but obviously I'll be wanting that next.  Thanks.

69,000m above jeb's outhouse was a slight exaggeration of "above the flight ceiling of conventional engines but annoying to get to suborbitally".

Yeah, it's generally a really good idea to grab the Terrier as soon as you possibly can in any new career-- prioritize that over just about everything else.  The Terrier is an amazing workhorse engine that seriously opens up worlds of possibilities, and it will stand you in good stead all the way through your career.  Even after you've maxed out the tech tree and are building elaborate missions to the outer planets, you'll still be using it.

A lot of players get it into their heads that "the Terrier is a vacuum engine" and think that means "don't use it in atmosphere at all."  Actually... what many folks don't realize is that vacuum is a lot closer than you think.  By the time you get to 10 km altitude-- which even a Juno can fly at-- you're already pretty close to vacuum, high enough that the Terrier gets quite close to its excellent vacuum Isp.  So you don't have to reserve it for space; just don't try to use it off the launch pad.  10 km and you're fine.

[klesh]

I'm really looking forward to seeing how the terrier is redesigned, if at all.  At present it strikes me as one of the uglier and more boring looking engines out there.  

[DaMachinator]

Ballistic missiles.

I suggest doing some target practice in sandbox before attempting this.

Edited June 16, 2016 by DaMachinator

[Rocket In My Pocket]

Yeah, those missions are really not worth the time or effort.

Not that they can't be done, once you get some practice you can pretty much eyeball where you'll have to be as you re-enter to hit your target. But there are way easier ways to get funds/rep.

That said if I do have to or feel like doing one of these for some reason, I typically build a very small plane, wrap it in a fairing, and send it up on a rocket, then de-orbit and glide back to a landing... not really the best way to do it, but it's the only way I've found that's any fun for me.

[Corona688]

T

54 minutes ago, Snark said:

Yeah, it's generally a really good idea to grab the Terrier as soon as you possibly can in any new career-- prioritize that over just about everything else.

I never really liked the Terrier.  Its efficiency is amazing, but it weighs a (literal) ton, which is a lot for the pitiful thrust it gives.  It's just about the worst possible weight balance in that respect -- only useful for larger craft, and for that you'll probably need several.  It's also not really a "lander engine" despite that being its stated purpose, it's shortER but not really helpfully so.  I like to build smaller yet and use the Spark.  Less efficient, but weighs so much less you can save just as much fuel from that.

I indeed hadn't paid any thought to using it in aircraft.  Thanks.

Edited June 16, 2016 by Corona688

[Rocket In My Pocket]

13 minutes ago, Corona688 said:

but it weighs a (literal) ton

According to it's part.cfg file as well as the wiki it weighs 0.5 which is half a ton?

[Corona688]

26 minutes ago, Rocket In My Pocket said:

Yeah, those missions are really not worth the time or effort.

Some of them pay a LOT of money though, which is the only reason I'm considering them.  That, and to stop them from perpetually clogging my queue when I could be seeing better ones.

[FullMetalMachinist]

14 minutes ago, Corona688 said:

Some of them pay a LOT of money though, which is the only reason I'm considering them.  That, and to stop them from perpetually clogging my queue when I could be seeing better ones.

Well, if you want to not see them offered any more, then accepting them is the opposite of what you want to do. 

As of 1.1.0 the contract system has a "weighting" system. This means that contracts you accept more often have more chance of being offered again, and contracts that you decline or ignore are offered less often. 

Edited June 16, 2016 by FullMetalMachinist

[Corona688]

48 minutes ago, Rocket In My Pocket said:

According to it's part.cfg file as well as the wiki it weighs 0.5 which is half a ton?

Within an order of magnitude! 

But I mean -- you can get five entire spark engines for that, which between them would have 50% more thrust with excellent efficiency anywhere from ground to orbit!  On the ground, one spark actually out-pushes the Terrier.  There's no better T/W ratio than the Spark's until you start getting up into things like mainsails, and nothing worse than the Terrier's except weird things like NERVAS and CRRAPIERs.

  If you only need a little thrust, the weight savings is immense.  I used to be able to get to orbit with one terrier and two sparks until they nerfed them somehow.

Edited June 16, 2016 by Corona688

[Snark]

1 hour ago, Corona688 said:

Its efficiency is amazing, but it weighs a (literal) ton

No, only half a ton (as R.i.m.P. points out), which is a pretty big difference.

1 hour ago, Corona688 said:

which is a lot for the pitiful thrust it gives

...What are you talking about?  60 kN, perfectly respectable for an orbital engine that's only half a ton.  Besides, for orbital maneuvering, it's not thrust that matters, it's fuel efficiency, and the Terrier really shines at that; the second-highest LFO Isp in the game, just barely behind the Poodle at #1.

1 hour ago, Corona688 said:

It's just about the worst possible weight balance in that respect -- only useful for larger craft, and for that you'll probably need several.

Not sure what you're talking about-- it does fantastic by itself, for the right size range.  If you find yourself with a craft that's so large that you need several Terriers, then you're probably better off just going to a Poodle.  A single Poodle has 4% more thrust than four Terriers, for 9% less mass, with 1.5% higher Isp, so it's a marginally better choice.  But it's pretty close.

For example, a Mk1 command pod, on top of a 2-ton LFO tank, on top of a Terrier, gives you a whopping 2800 m/s of dV in a tidy 3.6-ton package.  You can go an awful lot of places with that.

Swapping out a Spark for the Terrier in the above scenario will give you around 150 m/s more dV ... but carries with it a lot of disadvantages:  Have to climb a lot higher in the tech tree.  Screws up your 1.25m launch stack by sticking a .625m engine in the middle.  Has one-third the thrust.  And if you scale slightly larger (e.g. give it a 4-ton fuel tank instead of 2-ton), then the Terrier's higher Isp pulls out ahead for dV.

1 hour ago, Corona688 said:

It's also not really a "lander engine" despite that being its stated purpose, it's shortER but not really helpfully so.

Sure it is.  The thing that matters for a lander engine is:  Can lander legs mounted to the tank above the engine reach the ground below the engine, or not?  And for the Terrier, the answer is yes.  Even the smallest micro-landing legs can reach past the Terrier to the ground.  Works great.

1 hour ago, Corona688 said:

I like to build smaller yet and use the Spark.  Less efficient, but weighs so much less you can save just as much fuel from that.

Well, yes, the Spark is also a very good engine, and I love it a lot, and use it a lot.  But it's a complement to the Terrier, not a "better" engine.  Depending on circumstances, one or the other may be a better choice.

Things to like about the Spark, over the Terrier:

• It's a lot smaller than the Terrier, so for really little ships where the Terrier is too much engine, it's a better choice because its smaller mass more than offsets its lower efficiency.
• 50% higher TWR.

Things to like about the Terrier, over the Spark:

• 15% better fuel efficiency.  Given how hard it is to boost dV by piling on more fuel, due to the tyranny of the rocket equation, the extra efficiency really makes a difference.
• Available considerably earlier in the tech tree (and is on the critical path to other must-have parts anyway), so it's friendlier to early career.
• 1.25m form factor, so it fits much better in 1.25m rocket stacks.

The break-even point for Terrier-versus-Spark is around the scenario I describe above-- a 3.5-ton ship that's carrying 2 tons of fuel.  It's pretty close to a wash between the two, at that point.  Coincidentally, that happens to be roughly the size of a Mun lander (at least, the ones I use).  So for Mun exploration, Terrier-or-Spark is pretty much a toss-up if you happen to have both engines available.  However... when I'm exploring the Mun, it's usually very early career when I don't have the Spark yet, so it's usually a Terrier win for me.

Minmus tends to be more Spark-friendly, mainly because you don't need as much fuel, and certainly don't need as much thrust, so the Terrier is just way more engine than necessary and a single Spark does the job just fine.

For small, light unmanned craft, where I don't have to lug around a big heavy command pod:  yeah, the Spark is the clear winner there, I'll grant you that.  Craft that are under 2 tons should really not bother with a half-ton engine.

54 minutes ago, Corona688 said:

But I mean -- you can get five entire spark engines for that, which between them would have 50% more thrust with excellent efficiency anywhere from ground to orbit!

Except that you don't need the extra thrust when you're not vertically ascending, and the efficiency isn't "excellent", it's "barely adequate".  Better than an SRB, sure, but worse than just about any of the bigger engines.

It's a good choice when the ship mass is so low that using a light engine is really important.  But if you're piling on 5 or more of them, you get a lot more bang for your buck with the Terrier.

56 minutes ago, Corona688 said:

On the ground, one spark actually out-pushes the Terrier.

Well, sure, but you'd have to be nuts to use the Terrier on the ground.  It's a vacuum engine, it's what it's for.  On the ground at Kerbin, its fuel efficiency is hideous and its thrust is pitiful, can barely get off the ground.  So yeah, don't use it right off the launchpad; wait until you're above 12 km or so.  But criticizing the Terrier for being weak off the launchpad is like criticizing a fighter jet for having poor road handling:  it's not what it's for. 

And the only place where TWR matters that much is where you're doing a vertical liftoff from a heavy-gravity planet, which is not where anyone uses the Terrier anyway, so TWR is pretty much irrelevant.  It's good enough for an efficient Mun liftoff, and does pretty well even on Duna, which is plenty good enough.

[bewing]

I like the airborne contracts. Easy money. The thing is, you get a 100% refund on your plane at the end, so all you have to spend is the fuel cost. So, there are two kinds -- in flight below altitude x, and in flight above 16km to 19.9km. So yes, I assume that "in flight above" are the ones that annoy you.

As snark said, at tier 4, what you want is a little plane with 3 junos, 120 units of liquid fuel, and a flea or small rocket engine with enough LfOx -- that's always enough to get you at least one high altitude reading.

At tier 5, a little plane with a wheesley and two thuds can always take out two high altitude contracts in a flight. At tier 6, you have the panther. And sometimes at tier 5 you can get the panther on a contract.

(And the location that I enjoyed the most so far was "Valentina's Bar and Grill" at the NE tip of KSC. Honestly!)

[mk1980]

is that a new type of contract or did i miss something? afaik there are only 3 types of surveys - on the ground (usually seismic survey once the instrument is unlocked) - in flight *below* certain altitude and in flight *above* some altitude. the latter can be an arbitrary altitude as along as it's above the specified value (ie. passing over the spot with a capsule in orbit also counts).

or are you talking about a different type of survey i'm not familiar with?

[Corona688]

I am certainly not saying it's better to use a pile of ganged Spark engines than, say, one T45.  Just that the Spark is a lot lighter and more versatile than the Terrier.  The Terrier is fantastic for one and only one thing -- long burns on medium-sized craft in vaccuum.  I build smaller than that whenever I can get away with it, which makes the Terrier a pain to lug around.

Especially as dead weight on an aircraft.

Edited June 16, 2016 by Corona688

[Corona688]

51 minutes ago, bewing said:

I like the airborne contracts. Easy money. The thing is, you get a 100% refund on your plane at the end, so all you have to spend is the fuel cost.

Assuming it survives.  A specialized craft that has to ditch half of itself before it can climb to 39,000ft is going to cost something, and lose a percentage in retrieval after parachute landing.

Edited June 16, 2016 by Corona688

[bewing]

The highest any of my stock atmospheric contracts have ever specified was 19600m. I never have to stage or ditch anything, and my planes are always 100% controllable and landable -- assuming I can make it all the way to the contract point and back with the Lf in my tanks.

[Stoney3K]

4 hours ago, Snark said:

Actually, it's pretty easy-- you just have to be careful with your design, and think small.

I usually don't do a lot of that sort of mission, other than maybe one or two in early career for an infusion of cash and reputation.  However, I've found that it's not too hard to build a small jet + rocket plane that can get pretty much anywhere it needs to.

The Junos are so fuel-efficient that they can fly you a long distance from KSC with minimal fuel requirement.  When you get to the target site, you're flying at the Junos' operational ceiling, up around 10-12 km, which is high enough that the Terrier gets very close to its vacuum Isp (which is excellent).  So at that point, you just point your nose at the sky and kick the Terrier in the pants.

The reason I usually skip those missions is because they tend to pop up at the other side of the planet, and I really don't feel like spending an hour to cruise towards my target location on a pair of Junos (basically do nothing but fly forward and stare at the screen) just to do a temperature reading. And fly the entire part BACK again, even though those missions may be cheap to do, they waste too much of my time.

Trying to hit the spot from orbit will usually work, but that is limited to a certain altitude/speed combination if you want the mission to have any payoff.

[Corona688]

58 minutes ago, bewing said:

The highest any of my stock atmospheric contracts have ever specified was 19600m. I never have to stage or ditch anything, and my planes are always 100% controllable and landable -- assuming I can make it all the way to the contract point and back with the Lf in my tanks.

How exactly can you get to 19,000m with a Juno?  Or do you mean with upgraded engines?

Edited June 16, 2016 by Corona688

[Corona688]

1 hour ago, mk1980 said:

is that a new type of contract or did i miss something? afaik there are only 3 types of surveys - on the ground (usually seismic survey once the instrument is unlocked) - in flight *below* certain altitude and in flight *above* some altitude. the latter can be an arbitrary altitude as along as it's above the specified value (ie. passing over the spot with a capsule in orbit also counts).

or are you talking about a different type of survey i'm not familiar with?

As above, it's an exaggeration about the kind of mission that's frustrating me, every airborne mission I get is just a hair out of reach of my best air-breathing engines but the destination is difficult and costly to get to orbitally.

[Snark]

2 hours ago, Corona688 said:

The Terrier is fantastic for one and only one thing -- long burns on medium-sized craft in vaccuum.

Sure, and that happens to be a very wide variety of missions in KSP.  And it's worthwhile any time you have more than 3.5 tons or so of ship mass, which is an awful lot of the time.  It's hard to build a craft that's a whole lot lighter than that in a lot of situations.  It's an incredibly useful 2nd or 3rd stage for an orbital ascent vehicle that has a command pod on it, or as a sustainer stage for something smaller that's got a Spark on top of it.

And don't discount the fact that it's much "tech-cheaper" than the Spark.  Available earlier in the tech tree, doesn't require spending science points on a node just to get it (since it's en route to a path you need anyway), and that 1.25m form factor makes it incredibly convenient; the Spark is awkward to use in a stack, if the stuff on top of it is bigger than 0.625m.

Which is one of the reasons I'm strongly recommending it in this thread.  The OP's problem is how to handle those airborne missions, which tend to pop up a lot in early career.  Getting the Terrier's a lot easier than getting the Spark in those scenarios.  I've found that by the time I have the Spark, I no longer need to look at those airborne missions anymore, because there's better stuff to do elsewhere.

2 hours ago, Corona688 said:

makes the Terrier a pain to lug around.

Especially as dead weight on an aircraft.

...except that it works great for the specific missions that the OP is having trouble with, and is available really early in the tech tree.

3 hours ago, bewing said:

I like the airborne contracts. Easy money. The thing is, you get a 100% refund on your plane at the end, so all you have to spend is the fuel cost.

^ This.  Really nice to get the full cost back.

2 hours ago, Corona688 said:

Assuming it survives.  A specialized craft that has to ditch half of itself before it can climb to 39,000ft is going to cost something, and lose a percentage in retrieval after parachute landing.

Except that it does survive, completely, no staging, no losses, come in for an easy landing at KSC when done.  A small/light plane that has two Junos and a 2-ton LFO tank with Terrier can easily pop up (once) as high in the atmosphere as you like, then come back down and fly home again.  No staging required, don't ditch anything at all.

1 hour ago, Stoney3K said:

The reason I usually skip those missions is because they tend to pop up at the other side of the planet, and I really don't feel like spending an hour to cruise towards my target location on a pair of Junos (basically do nothing but fly forward and stare at the screen) just to do a temperature reading. And fly the entire part BACK again, even though those missions may be cheap to do, they waste too much of my time.

That can certainly be a concern.  I've noticed (for me, at least), it seems that in the really early part of career, those missions generally crop up within easy distance of KSC, so they're reasonably quick to get there and back.

1 hour ago, Corona688 said:

How exactly can you get to 19,000m with a Juno?

You don't.  You get to around 10-12 km with the Juno, then activate a rocket boost to pop up higher to the target altitude.  A small amount of fuel & a small rocket engine will do the trick, as long as your craft is small and light.  Later on you can have fancier jet engines, of course, but for very early career, a couple of Junos accompanied by a Terrier can get you where you need to go.