New Eve dV?

[EdFred]

So, I shelved KSP for a long time since I pretty much did everything in it. But I've started futzing with it again. I see that the 4500 --> LKO is no longer the case, Is there a new list of dV to orbit for Eve and Laythe? Duna seems to be about the same as it was in .90 - but the atmo is pretty thin there to start with. I'm thinking about heading back to the purple dot, but no idea if 12,000 is still the magic number or not. Edited November 20, 2015 by EdFred

[quasarrgames]

Eve is now 7500-8000 delta v to ascend from sea level, depending highly on the launch trajectory. from the highest peaks it is possible to shave 1000-1500 m/s off the orbital demand, putting it JUST BARELY within the realm of theoretical SSTOing. However, entering the atmosphere can now get pretty steamy, so good luck with landing and taking off again- you'll still need it.

[EdFred]

Thanks. I'm assuming it's still a vertical-ish burn through at least 15k

[Xyphos]

at sea-level, Eve has an atmospheric pressure of 5 Kerbins, meaning that spaceplane parts are very effective up to 35km - 45km.
you just can't use air-breathing engines as Eve is mostly CO2.

you many want to try to make a heavy lander with spaceplane tug for a lower ascending stage to get you up high enough to achieve orbital velocity with the least amount of drag.

remember that majority of your dV is lost to drag, but since the atmosphere is so dense, you can get away with using large tanks and smaller engines such as the new Tortodial Aerospike, so long as you don't attempt a too steep of a climb. Edited November 20, 2015 by Xyphos

[EdFred]

I'm guessing you didn't look at the links in my signature ;)

[Kobymaru]

[quote name='EdFred']I'm guessing you didn't look at the links in my signature ;)[/QUOTE]
That's not a particularly saxay craft. Quite the pre-1.0 pancake, in fact. Maybe you could have shaved off a few tons if you would have made it a little more streamlined?

I saw a guy with a ridiculously small lander that could bring up one Kerbal. I'll link him if I find it again.

[EdFred]

Yes, it was quite un-aerodynamic, it didn't need to be aerodynamic under the old system - and being streamlined wasn't a requirement. It was also created to ascend from Eve's sea level. The first 8,000dV is easy, the last 4,000 is the difficult part. I actually did have one that wasn't so ostentatious, I just didn't document it - since that one above was for the Eve Rocks challenge.

[Kobymaru]

[quote name='EdFred']Yes, it was quite un-aerodynamic, it didn't need to be aerodynamic under the old system - and being streamlined wasn't a requirement. It was also created to ascend from Eve's sea level. The first 8,000dV is easy, the last 4,000 is the difficult part. I actually did have one that wasn't so ostentatious, I just didn't document it - since that one above was for the Eve Rocks challenge.[/QUOTE]
Oh that was actually for pre-1.0? Well then congratulations to your great craft!

[KerikBalm]

be aware now that heating both on the descent and the ascent is not to be taken lightly.
Also under the new system, TWR suffers greatly at high atmospheric pressures.
From Eve sea level, the Aerospike has the best Isp, however, a few Km up, it is the mammoth/vector.. and then higher up, the aerospike again.
Also, while on the surface, especially at sea level, the thick atmosphere makes your solar panels not work well at all.

For a brief moment in 1.04, SSTO from the surface of Eve was possible if you took off from the highest location.
However, drag has since increased at higher altitudes, and heating is more intense... and it was already borderline with heating in 1.04.
That SSTO had very very flimsy landing gear, and no one was able to get it through reentry, land it, and get it back into orbit.
With 1.05, I don't think anyone has tried, but the changes are generally thought to make the situation even worse.
Still... in 1.04, a stock SSTO from the surface of eve was possible

Anyway, the dV maps, I like this one the best:
[img]http://i.imgur.com/iXtul2v.png[/img]

This one claims only 6km/s... but I think that is dubious, or assuming a launch from an elevated position:
[img]http://i.imgur.com/8jGWLCg.png[/img[

[EdFred]

That new dV map is most helpful. I was testing last night however to see what it took for 80km LKO and I was able to get it done for between 3000 and 3100 dV so some of those numbers may be a bit conservative.

[Racescort666]

[quote name='KerikBalm']be aware now that heating both on the descent and the ascent is not to be taken lightly.
Also under the new system, TWR suffers greatly at high atmospheric pressures.
From Eve sea level, the Aerospike has the best Isp, however, a few Km up, it is the mammoth/vector.. and then higher up, the aerospike again.
Also, while on the surface, especially at sea level, the thick atmosphere makes your solar panels not work well at all.

For a brief moment in 1.04, SSTO from the surface of Eve was possible if you took off from the highest location.
However, drag has since increased at higher altitudes, and heating is more intense... and it was already borderline with heating in 1.04.
That SSTO had very very flimsy landing gear, and no one was able to get it through reentry, land it, and get it back into orbit.
With 1.05, I don't think anyone has tried, but the changes are generally thought to make the situation even worse.
Still... in 1.04, a stock SSTO from the surface of eve was possible

Anyway, the dV maps, I like this one the best:
[URL]http://i.imgur.com/iXtul2v.png[/URL]

This one claims only 6km/s... but I think that is dubious, or assuming a launch from an elevated position:
[img]http://i.imgur.com/8jGWLCg.png[/img[[/QUOTE]

That is a great dV map. I like the Kraken emblem. For career mode, I found that transfer window planner was better (since I usually have multiple flights in progress) although just like the dV maps, I usually end up adding a 5-10% buffer to everything.

[Meithan]

[quote name='EdFred']That new dV map is most helpful. I was testing last night however to see what it took for 80km LKO and I was able to get it done for between 3000 and 3100 dV so some of those numbers may be a bit conservative.[/QUOTE]

If you optimize for cost efficiency (funds per tonne of payload) and not for lowest-Δv-to-orbit, I've found that 3400-3500 m/s is about right for the typical ascent.

[EdFred]

[quote name='Meithan']If you optimize for cost efficiency (funds per tonne of payload) and not for lowest-Δv-to-orbit, I've found that 3400-3500 m/s is about right for the typical ascent.[/QUOTE]

I never worry about cost! I pretty much play in the sandbox as I have done the career To the point I had enough money I could do whatever mission I wanted , and don't feel like doing it again.

Interesting that the delta V map was based on cost and not actual delta V. I would have not thought to have created one with that parameter

[KerikBalm]

First, I've gotten red for posting those maps, just FYI, I did not make them, maybe I should link to the thread where they were first posted if I can find it.

EdFred-
I don't think it was based on cost....
But I have a feeling that it is listing a "typical" vacuum dV readout... which is highly variable when it comes to what atmospheric dV that is, and the total dV expended, vs simply the difference in the vacuum dV readout from start to finish.


If you start with 3000 atmospheric dV, you actually can use more than 3000 m/s of dV, because your Isp goes up as you do, and with a proper gravity turn, you spend most of that dV in near vacuum conditions.

Then again, if you start with 3400 vacuum dV, you'll actually have a lot more dV available if that is 3400 vacuum dV from a mammoth vs a terrier.
Likewise a reliant vs swivel will give you different dV values needed if you only look at vacuum or atmospheric. The ones with lower differences between vacuum and atmospheric Isp are going to give you lower "dV required" to orbit if you just use the vacuum readout

Measuring dV for an atmospheric ascent to orbit is a rather complicated proceedure...
So yea, it is conservative, but I'd guess you were also trying to be rather optimal... I'm still curious how you even measured the dV you expended getting to orbit.

TL:DR
If you measure only vacuum or atmospheric dV, the "dV required" will be different for craft using different engines, even if the aerodynamics and TWR are the same.
There are so many variables, and this is a guideline... you should easily be able to get underneath the stated values (which I think are measued as vacuum dV)... other craft will need even more (pancake rockets, or just really wide payloads in a really wide fairing)

[technion]

[quote name='EdFred']I never worry about cost! [/QUOTE]

I only play career, and cost of rockets still isn't a huge factor.

In early games, building upgrades needed for manoeuvre nodes and surface samples cost way more than any launch I would put together, and later, you find yourself with so much cash it stops being relevant.

[Meithan]

@EdFred:

I don't think those maps were computed optimizing for cost either.

As KerikBalm pointed out, the atmospheric Δv's are not unique values since they depend (even more strongly now) on a variety of factors (rocket streamlining, per-stage atmospheric TWR and Isp curve of engines, ascent profile, piloting skill, etc.). Because of this, I wouldn't think the stated values are optimal values: I'd think they're intended to be representative "typical" values with an "average" rocket design / flight profile / etc. It's better to err on the safe side in this case, since there can be a large variability in actual performance.

And 3500 m/s for ascent to LKO is an approximate value that reflects my experience in general. I measure this with MechJeb, by the way, which shows you how much was lost to gravity, drag and steering, with Δv_spent = final_orbital_velocity + (gravity_losses + drag_losses + steering_losses).

@technion:

It's probably more my optimization OCD than anything else. One has to optimize for [i]something[/i], right? :P.

But I don't feel I have got to the point where money is irrelevant yet (I've about 12 millions in the bank ... is that enough?). Edited November 20, 2015 by Meithan