DeltaV to LKO changed?

[cami]

Hi there,

maybe my memory is tricking me, but I believe deltaV from Kerbin to LKO was about 5 km/s. But somehow I use only 3km/s. Did I mess up with some setting? I also noticed the spacecraft hardly accelerating while the g-meter is at 2g.

Ground gravity is 1g, v1 = 2250 m/s. Kerbin radius is 600 km, LKO altitude is 80 km.

I only use stock parts, mod list:

• Kerbal Engineer
• Environmental Visual Enhancements
• Docking Port Alignment Indicator
• PlanetShine
• ScienceAlert
• Stock Visual Enhancements
• Kerbal Alarm Clock

Any numbers in the save file / settings files I could check that affect this?

Regards, cami

[AngrybobH]

dV to LKO is ~3.4km/s depending on TWR, drag, gravity turn profile, plus some others. It's been that way since I started playing.

wouldn't 2g on the meter when launching mean that 1g is gravity and the other g is your accel? I don't know, I never really look at the g meter. I use kerbal engineer and mechjeb to see TWR and accel in m/s^2.

[cami]

Sort of, accel is at least g-force minus 1g (depends on attitude and altitude). However I saw 2g force and only about 0.1g accel, which doesn't fit the math.

Ok if you have 3.4km/s then this seems to either really have changed, or my memory is wrong. I always used a little less deltaV than most others. :p

[Harry Rhodan]

57 minutes ago, cami said:

maybe my memory is tricking me, but I believe deltaV from Kerbin to LKO was about 5 km/s.

Yeah, before version 1.0 more than three years ago.

[Snark]

Moving to Gameplay Questions.

[wild_dog]

I've been using The following Image from This steam post as a handy delta V guide. Technically It is for version 1.3.0, but for me it has proven accurate enough.

As stated previously, delta V to LKO at 80 is 3400 m/s, however I have been able to reach a 100km orbit with around 3200 m/s when using MechJeb and a slightly customized launch profile and limiting MaxQ.

Basically, this means I keep speed a bit lower while deep in the atmosphere to avoid burning delta V unnecessary fighting the drag forces associated with reaching speeds around Mach 1.

I do not know if it has recently changed from 5000m/s delta V, but I can state with certainty that it is around 3400 currently.

[Gargamel]

On 9/20/2018 at 5:00 PM, wild_dog said:

The following Image from This steam post 

Which is odd, as it it's originally from these forums

[swjr-swis]

6 minutes ago, Gargamel said:

Which is odd, as it it's originally from these forums

Which in turn is not really so odd, considering it's the Steam forums we're talking about...

[OhioBob]

I seem to recall the number back in the pre-1.0 days as being about 4500 m/s.  They completely redid the aerodynamics with the release of v1.0.

The old aero model was just a placeholder.  It used some very simple formula to compute factors such as drag coefficient and surface area.  The surface area formula was particularly bad, turning everything into a flying pancake.  This resulted in huge drag losses, which is why it took so much delta-v to reach orbit.  The new aero model is far more lifelike.  Drag losses are nowhere near what they use to be, so it now takes about 3400 m/s to reach orbit.

[swjr-swis]

40 minutes ago, OhioBob said:

I seem to recall the number back in the pre-1.0 days as being about 4500 m/s.

 

One of several dV maps of back then confirms this:

Spoiler

As found on

 

 

[Gargamel]

14 hours ago, swjr-swis said:

One of several dV maps of back then confirms this:

I don't need a map to confirm it.   I spent about a half a year trying to figure out why my ships were suddenly way more efficient at launching. 

[swjr-swis]

55 minutes ago, Gargamel said:

I don't need a map to confirm it.

I should've worded that differently. Just backing up your statement, really.

[Gargamel]

3 minutes ago, swjr-swis said:

I should've worded that differently. Just backing up your statement, really.

Oh I Know :D, I was just venting long held up frustration over "why is this working so well!?", which actually is a problem when my designs sort of wanted all the launcher stage fuel to be used up.  So yeah, I can use the remaining launcher fuel for injection burns, but now my lander, which is humping a disposable fuel tank below the landing legs, is forced to ditch it early, and that fuel is just lost. 

Nobody expects the laws of physics to change!

Unless they read the patch notes. 

Edited September 22, 2018 by Gargamel

[OhioBob]

49 minutes ago, Gargamel said:

Nobody expects the laws of physics to change!

Technically, the laws of physics didn't change.  KSP used the same drag formula both before and after v1.0.  What changed were the numbers that got plugged into the drag formula.

Starting with v1.0, KSP began using the actual geometry of the rocket to determine the surface area exposed to the air flow, and to compute the drag coefficient.  The thing that most significantly affected the delta-v to orbit was the surface area.  Prior to v1.0, KSP used a very simple formula that estimated the cross sectional area as a function of mass.  For rockets, it was a really bad formula that grossly overestimated the area.  This resulted in huge and unrealistic amounts of drag.

 

Edited September 22, 2018 by OhioBob

[Gargamel]

16 minutes ago, OhioBob said:

Technically, the laws of physics didn't change.  KSP used the same drag formula both before and after v1.0.  What changed were the numbers that got plugged into the drag formula.

I know... but I was going for a Monty Python-esque quote... and failed miserably.  

[GuyWithGlasses]

3 minutes ago, Gargamel said:

I know... but I was going for a Monty Python-esque quote... and failed miserably.  

Not at all (nobody expects the spanish inquisiton! Lol)

 

[cami]

I just wanted to step in and thank you for all the comments. I didn't notice this came with 1.0 as I was mostly using spaceplanes in vanilla at that time and their mass ratio didn't change much (about everything else in the design did, but that was to be expected).

I also switched to Realism Overhaul shortly after. Recently my gf started the game in vanilla.

4.5km/s is still found in my old spreadsheets and I remembered using two stages at 2.3 km/s dV, so just like you I was quite surprised these old designs could easily escape the kerbin system.

Edited September 29, 2018 by cami