If I ever make it back from Eve

[Reinhart Mk.1]

Just now, The_Cat_In_Space said:

War Thunder

thems is fightin words

[Chel]

Just now, Reinhart Mk.1 said:

thems is fightin words

I also have played IL-2 Bird Of Prey on the DS if that helps

[Reinhart Mk.1]

4 minutes ago, The_Cat_In_Space said:

I also have played IL-2 Bird Of Prey on the DS if that helps

lol im just joking. i love flight sims in general

[GRS]

If only i was better in planes...

Well, Eve Landers shouldn't be too hard, just try avoiding making your lander fat, use some top shields, that big lander used 6 Lower shields, 1 Top shield for stability and some reaction wheels below the Top shield, yet it'll still flip in like 1000 m/s, it was really OP.

[Reinhart Mk.1]

4 minutes ago, GRS said:

reaction wheels

would this help for keeping it stable on a small craft? i added vector engines but eventually it still flipped and exploded

 

[GRS]

17 minutes ago, Reinhart Mk.1 said:

would this help for keeping it stable on a small craft? i added vector engines but eventually it still flipped and exploded

 

Depends, on where you placed it (according to the torsion physics rule) and when it comes to Eve, be careful with gravity turns, your TWR should be at least 1.2 for a save ascent, then quickly nose up completely verticaly, gravity turn better start as you approach 1000 m/s (or try using prograde node to stay safe form being flipped), then try staying at that speed until you got to >80 km then burn horizontaly, get Trajectories mod so you can accelearate to a bare-ish "beyond atmo" then burn all fuel in the Vector stage, finish orbital burn by Orbital stage pointing slightly above "Horizon" and you're in Orbit ! (About the bigger ones...i burnt fully vertically until i'm away from that atmo, then steep turn above the atmo and burn anything left in the 3 Vector core stage horizontaly and release an orbital stage, i also got OCD, i call orbits stable when they has 0.000xxx eccentricity)

Edited February 20, 2019 by GRS

[herbal space program]

1 hour ago, Reinhart Mk.1 said:

lol my bad, but damn i was actually a certified ace hahahah. it only makes sense i'd be "promoted" to space travel. irl it would make sense

Have you built a space plane yet? It's not so hard to land on Laythe and return with a Rapier/Nerv-based SSTO.  Duna is a bit harder to do that way, but well within reach. For me, designing and flying planes added huge play value to the game.

Edited February 20, 2019 by herbal space program

[Reinhart Mk.1]

14 minutes ago, herbal space program said:

Have you built a space plane yet?

yeeeeeep it needed to be refueled but i got it into orbit

I've gotten better at building them and i'm trying to make a "fleet" that makes sense and isn't too flashy or expensive

[Reinhart Mk.1]

YOOO I THINK I USED THE OBERTH EFFECT RIGHT

nvm, still the same amount of dV if i orbit then do the maneuver as opposed to just straight up into orbit of the sun then do the maneuver

[Kerbinchaser]

What, haven't you heard? No one ever comes back from Eve. That's why the word "never" has Eve in it.

Edited February 20, 2019 by Lo Var Lachland

[Chel]

4 minutes ago, Lo Var Lachland said:

What, haven't you heard? No one ever comes back from Eve. That's why the word "never" has Eve in it.

Nobody comes back? Time for a little test!

[Reinhart Mk.1]

5 minutes ago, Lo Var Lachland said:

What, haven't you heard? No one ever comes back from Eve. That's why the word "never" has Eve in it.

YOU UNDERESTIMATE MY POWER

[GRS]

1 hour ago, Lo Var Lachland said:

What, haven't you heard? No one ever comes back from Eve. That's why the word "never" has Eve in it.

...Well...you wrote it wrong, it should be "No one NEVER comes back from Eve" so that at least someone already did.

*Lands on Eve then comes back from there*

Also suggestion for Eve entries, do it in multiple passes and strap some top shields for stability.

Edited February 20, 2019 by GRS

[StrandedonEarth]

53 minutes ago, Lo Var Lachland said:

What, haven't you heard? No one ever comes back from Eve. That's why the word "never" has Eve in it.

I can't believe I haven't posted this is this thread yet...

[Reinhart Mk.1]

I HATE Eve, so so much.

[Reinhart Mk.1]

I couldn't even land my new ship, it was too big but i was also too impatient, you win again Eve

[GRS]

56 minutes ago, Reinhart Mk.1 said:

I couldn't even land my new ship, it was too big but i was also too impatient, you win again Eve

Screenshot ??? Maybe you forgot a top shield, or your descend speed is higher than safe speed, or its too fragile.

[KerikBalm]

On 2/18/2019 at 6:53 PM, Laie said:

Interestingly, it doesn't. The WH is quite heavy itself, and on a last stage, it can easily make up the bulk of the (dry) mass. That's a delta-V killer. If your payload is nothing more than a command pod, or, even worse, a service bay with command chair, you should look for more lightweight engines.

 

Yes, if your payload is that light... but if on the other hand you're trying to lift ore off the surface for a contract (and not abusing an exploit for those sort of contracts), or trying to lift many kerbals at once (with life support mods, so a chair isn't exactly very viable) to get many kerbals leveled up in one flight, or making an Eve SSTO that uses ISRU (its just barely possible),  then the wolfhound starts to look appealing again

On 2/18/2019 at 6:39 PM, Laie said:

Nah, the Vector can't be beat in that game. MH or not, no other engine comes even close in thrust-to-cross-section. And it's among the most efficient to boot. Hold on, I did a thing a while ago...

[*graphs snipped* ]

1. top left: ISP, simple enough.
2. top right: burn time you get if you load down an engine with as much fuel as it can carry (TWR=1, includes mass of tanks)
3. the impulse you get out of a maximally-fueled stack. That is, take engine X, load it up with fuel until TWR=1, burn it until empty. How many kN*s of thrust will come out?
4. The same, but divided by engine thrust. The unit would be seconds, and while I don't quite know what it means, I take it as a kind of Eve-specific impulse that somehow mashes in TWR.

I didn't include the Vector, but it's ISP is identical to the Mammoth and the TWR a little worse. You can expect it to be slightly below the Mammoth in 2) and 4).

3) gives you an idea of the importance of TWR. Notice how the Twin-Boar outperforms the Mainsail at any altitude, even though it's ISP is slightly worse? That's simply because it can carry more fuel to burn. Even more pronounced between Rhino and Poodle. And do you notice how the Aerospike sticks to the bottom of the plot?

4) manages to represent my personal idea of an engine's worth quite well, even though I cannot express it's meaning in scientific terms. The Aerospike simply fails to deliver, while the humble Mainsail isn't all that bad. Still worse than the Vector, of course, and once you start to think about the number and size of stacks, it becomes Vector, Vector, Vector.

The one downside of the Vector is it's high cost. If you care about money, you should bring an ISRU kit and don't fret too much about building the smallest possible rocket. When fuel is free, cheap gas-guzzlers become interesting.

Well, I was wondering about the mastadon's smallest variant. It has more thrust than the Vector, but I'm not sure its smallest variant fits on a 1.25m stack. Also the variants have weird drag properties, but it was one of the ones I was unsure about

As for 4) you've just made #2 again silly - that is why its in seconds :p  Burn time is fuel consumption / amount of fuel it can lift. The amount of fuel it can lift is determined by its thrust. An engine with 2x the thrust lifts 2x the fuel, but if the fuel consumption is 2x as high, then you've got the same burn time. Thrust is roughly equivalent to fuel consumption (adjusted for Isp), total impulse is roughly equivalent to fuel consumed (adjusted for Isp differences). 3, the total impulse, is essentially burn time * thrust, adjusted for Isp. Then by dividing that by thrust for #4, you're essentially getting an Isp normalized/weighted burn time - I think.

A don't find graph 3 to be very useful, because it weights all stacks the same, regardless of if they are 1.25m stacks, or 3.75m stacks, they should be weighted by cross sectional area.

As for the aerospike, graphs 1,2, and 4 make it look like the best engine below the first 4-5km of Eve, and again after about 25-30km on Eve. So the lesson here would be to land at a relatively high altitude, and them use mammoths/vectors to get you up to about 25-30km, and then aerospike stages after that (or since aerospikes are OK in between that, what I personally like is an asparagus rocket with an aerospike as the core engine, so the aerospike is firing the whole ascent).

In my hellhole modded eve with 10 Atms, the aerospike is the only option for surface ascents... I don't think I've actually managed an ascent from sea level on my modded eve yet, but I've got suborbital in space. 10 Atms is really really hard to deal with using stock parts. The aerospike is the only option. The same would go if you were trying to ascend from a low altitude on Jool: no option but the aerospike (or sort of cheaty stock propellors)

[godemperorzack]

11 hours ago, herbal space program said:

Don't I know it! Remarkable how this exercise converged to the same general idea for both of us:

https://imgur.com/a/7jFsTG2

 

Figuring out how stay stay behind all those heat shields and stage them off without exploding my ship was one of the toughest things I ever did for sure. The rest of it was fairly plug-and-chug

Yup, I feel your pain (or is it the reentry heat?)!

That is pretty interesting how we had somewhat convergent designs!

Edited February 20, 2019 by godemperorzack

[GRS]

Here's my Eve and back direct ascent style for one Kerbal during the Evar entry, it actually tumbled (flipped) in like 50 km @ 2300 m/s because of more drag in the lower shields...

Like this...

The explosion is harmless, i did this on purpose so that it looks like Mary Poppins...

Kinda...

That is an unperfected version because i forgot some Ladders for the lower transfer pod.

Steep orbital turn beyond atmo.

What lies behind that fairing...

Full rocket.

Used Onion Staging to get rid of Mastadon boosters.

Removing Mammoth "Boosters".

Escape burn with some Asparagus staging that starts with the 7 Vector powered Ascent stage core, this rocket contain traces of my old tech which was first made in my first days.

Rocket looks like this in escape trajectory.

Powered capture.

A newer version doing inclination burn.

Then start aerobraking...(after a Retroburn in Apoapsis)

(Yes, your eyes are all good, this rocket used only Chemical engines)

Edited February 20, 2019 by GRS

[Laie]

6 hours ago, KerikBalm said:

A don't find graph 3 to be very useful, because it weights all stacks the same, regardless of if they are 1.25m stacks, or 3.75m stacks, they should be weighted by cross sectional area.

3) is dominated by raw power. ISP and dry mass is mashed in, but ultimately a more powerful engine will carry more fuel and thus create more impulse. That's why I felt the need to divide by something to make them comparable again, and that's how I arrived at 4).

Impulse per cross-section might actually be a more useful metric. Can I simply assume drag to be proportional to area? AFAIK there are noticable differences...

6 hours ago, KerikBalm said:

As for 4) you've just made #2 again silly

Well, they don't look quite the same, do they? I think #4 puts more emphasis on TWR. But ultimatley it tells us that 1kN of Aerospike will, for a large part of the ascent, be less useful than 1kN of Mainsail.

6 hours ago, KerikBalm said:

As for the aerospike, graphs 1,2, and 4 make it look like the best engine below the first 4-5km of Eve, and again after about 25-30km

In principle, yes. At first it has superior ISP, peroid, and towards the end it has a pretty high TWR for it's ISP. Beware that the plot cuts off at 30km, though -- too early for the Rhino or Poodle to be fully online.

6 hours ago, KerikBalm said:

Well, I was wondering about the mastadon's smallest variant.

Attachment fits 1.25m but the engine bell is 2.5m. ESL and TWR are ever so slightly better than the Mainsail's but it should still be in the same ballpark. If you go for cost, it may be interesting... but as long as you're going for lowest mass or dV, it's nowhere near the Vector.

[Snark]

On 2/16/2019 at 12:57 PM, Reinhart Mk.1 said:

well not the WHOLE way up but the majority, now im currently back in VAB trying to figure out WHAT STRUTS I HAVE TO PUT IN THE RIGHT SPOT SO THIS THING IS STABLE. Honestly it's just my pride at this point, i could easily skip this but i just can't. why did they even make it possible to land on this planet hahahaha

One thing to bear in mind is that the ascent profile really matters.  You'll want to go pretty much straight up for about the first 20 km, then start a gravity turn.

But even "go straight up 20 km" isn't enough to know-- it really makes a huge difference how fast you're going.

In particular, you get the ideal efficiency (i.e. least amount of wasted dV) if your ship is traveling right at terminal velocity the entire time.  If you're going too fast or too slow, you'll waste a lot of dV.

• Too fast (i.e. faster than terminal velocity) and you'll waste lots of dV to aerodynamic drag.
• Too slow (i.e. slower than terminal velocity) and you'll waste lots of dV to gravity losses.

Don't get me wrong, big aero and gravity losses are inevitable when climbing off Eve, which is why it's so hard.    But "be right at terminal velocity the whole time" gives the optimum tradeoff between the two.

Unfortunately, knowing "what's the terminal velocity" is a tricky problem, since not only does it depend heavily on the aerodynamics of your ship, but also it changes (a lot) as the atmosphere thins out with altitude (and also changes every time you stage something away).

So it'll take some tinkering and probabl some trial-and-error to work out the "Goldilocks" speed during ascent.  The main takeaway point, here, is to understand that there exists an optimal speed, and simply "floor it and go as fast as I can'" isn't necessarily the right answer.

(This is usually never an issue on Kerbin, because the atmosphere is so much thinner than Eve, and drops off more rapidly with altitude.  Unless you have a seriously overpowered rocket, you'll never "catch up" to your terminal velocity on Kerbin, since the terminal velocity rises faster than your rocket's speed does.  Therefore, on Kerbin, the "right" answer almost always is "floor it and go as fast as possible".  But on Eve, that's not the case.)

Also... make sure your rocket's as streamlined as you can make it.  Because that lowers the aero losses, which raises your terminal velocity, which lets you climb faster, which lets you reduce gravity losses as well.

And if you can land somewhere significantly higher than sea level, that will also take a large chunk out of the amount of dV needed.

[SnakyLeVrai]

I've designed this bad boy for hauling my Kerbals back to orbit. It has a lot of dV left when circularized, they'll use it to rendez-vous with their interplanetary ship, which is bigger and way more comfier

Tested and approved!

KER dV information is accurate: I've added a 575kg weight in the VAB to simulate the mass of the 6 Kerbals in their seat (they barely reach 575kg anyway...).

[Kerbinchaser]

14 hours ago, GRS said:

...Well...you wrote it wrong, it should be "No one NEVER comes back from Eve" so that at least someone already did.

*Lands on Eve then comes back from there*

Also suggestion for Eve entries, do it in multiple passes and strap some top shields for stability.

But...That's not grammatically correct...

[herbal space program]

2 hours ago, Snark said:

One thing to bear in mind is that the ascent profile really matters.  You'll want to go pretty much straight up for about the first 20 km, then start a gravity turn.

But even "go straight up 20 km" isn't enough to know-- it really makes a huge difference how fast you're going.

In particular, you get the ideal efficiency (i.e. least amount of wasted dV) if your ship is traveling right at terminal velocity the entire time.  If you're going too fast or too slow, you'll waste a lot of dV.

• Too fast (i.e. faster than terminal velocity) and you'll waste lots of dV to aerodynamic drag.
• Too slow (i.e. slower than terminal velocity) and you'll waste lots of dV to gravity losses.

 

I feel like based on my experience that this doesn't really work out to be true in the game, but maybe I'm underestimating TV on Eve for the type of vehicle that is competitive. In challenges, the ships that make it to orbit with the least vacuum dV expended seem to be the skinniest possible rockets with the highest TWRs,  that basically tear a narrow hole in the atmosphere locked dead to prograde pretty much the whole way. You can see a couple of examples from myself and @Laie above.  Mine made it to LEO from sea level for under 6.7km/s, and could do significantly better than that if I resorted to McJeb. Setting aside the TV question, I can say with some confidence that to stay strictly prograde for so much of your profile, you need to start your gravity turn much earlier than 20km. On my best ascents, I started mine around 4km and was already pitched to 45 degrees not far above 20km. Another thing to bear in mind is that Eve's atmo stops at only 90km but weighs 5 times as much as Kerbin's, so its pressure drops off much more steeply above 25km, causing TV to rise sharply up there and making it more economical maybe to eat some drag losses down lower so that you don't pay even more dV back in gravity losses up high. IOW, I think it's complicated!

Edited February 20, 2019 by herbal space program