Should I invest time in learning 1.0.2 aero?

[theend3r]

I'm not saying it doesn't work, I'm saying its now more efficient to not use it. Every time you shed those boosters, you are losing thrust, and having to spend more time going vertical (gravity loses) and spending more time in the deeper part of atmosphere (more drag). You're better off to use the same design but without asparagus, that way when you drop the boosters, your main stack has a higher TWR than what you would had on the launch pad with full fuel and no boosters (in other words your TWR is always increasing until you get to your second main stack stage); you can punch through the earlier part of the atmosphere quicker while doing a proper gravity turn to get yourself horizontal.

I see your point but it depends on the circumstances. Some testing needs to be done to verify different setups. Or has it already been done?

Edit: grammar

Edited May 7, 2015 by theend3r

[magnemoe]

Asparagus staging is a thing of the past. The fuel efficiency on paper that you would have got from the old aero model is negated by the extra drag from the boosters, not to mention complications from the thrust lost from shedding these boosters early in the ascent. Best advice for rockets in the new aero, just like FAR, is to design your rockets like real world rockets: Tall and sleek, and design your rockets so that any boosters added are for providing extra thrust early on, not as a means to add extra dV.

As for the fins, that's just something that may or may not be required depending on how much control your rocket has (engine gimbaling, reaction wheels, RCS, etc.) or how tall/short it is (shorter tends to require more fins). Real world rockets these days typically do not have tail fins because much of their stability comes from the engine gimbaling. But the Saturn V had fins because they had to sacrifice a bit of the gimbaling capabilities to have the thrust needed to get the rocket off the launch pad, plus the S-IC was very massive and lowered the center of mass of the rocket significantly compared to other rockets. Again, it will vary between rocket designs.

Tell that to delta heavy. No delta heavy does not use crossfeed as its complicates stuff a lot and TWR is far higher than in KSP anyway reducing the benefit.

My standard heavy launcher uses crossfeeed, 1x2 core with orange tank on top, two orange tanks with mainsail as boosters. yes payload faction and fairing is larger than real world rockets.

Else you are right that long rockets are more stable, if you have an oversize fairing this will increase drag in front and you will need more fins. too extreme size and you might want to drop the fairing. Found that for satelites a 1.25 m nosecone on top of an octo core, mechjeb, battery and science on the core then 1.25 m tank with 48-7S behind tend to works better.

The T30 needs fins as it don't gimbal at least if its not very sleek design. I feel its an gap between the 1.25 meter and 2.5 meter parts, and I end up using plenty of stubby skipper designs.

[foxkill2342]

If you like it, keep it. If you don't like it change the physics.cfg values to 1.0.

[mrclucks]

That's basically the reason why I prefer the 1.0.2 aerodynamics over the 1.0 aerodynamics. In 1.0, my rockets just ignored the atmosphere, while I have to pay some attention to design and piloting in 1.0.2. It also helps that 1.0.2 feels more similar to FAR, which I used for almost a year before 1.0.

I was either unclear or you didn't read everything.

My 1.0 rockets didn't ignore the atmosphere. I used the aerodynamics tool (f12) to design and fly my rocket. If I designed something in 1.0 that wasn't very aerodynamic then it would flip over. I had a aerodynamic profile in front and fins in the back, which should keep it prograde. Less drag in front and more drag(fins) in back, coupled with a lower COM should mean that it flys prograde.

Unless I'm missing some vital information about aerodynamics, the rocket should fly

[Jouni]

I was either unclear or you didn't read everything.

My 1.0 rockets didn't ignore the atmosphere. I used the aerodynamics tool (f12) to design and fly my rocket. If I designed something in 1.0 that wasn't very aerodynamic then it would flip over. I had a aerodynamic profile in front and fins in the back, which should keep it prograde. Less drag in front and more drag(fins) in back, coupled with a lower COM should mean that it flys prograde.

We just had different expectations.

As I said, I had been playing with FAR for almost a year. Compared to that, 1.0 felt like the atmosphere wasn't there. Rockets could fly with very high angles of attack, and it usually required deliberate effort to make them flip. On the way down, the atmosphere definitely wasn't there, as pods could crash into mountains at supersonic speeds.

Unless I'm missing some vital information about aerodynamics, the rocket should fly

In my experience, there are two main reasons why reasonable-looking rockets might flip. Either the angle of attack is too high, or you're flying too fast. The latter happens often in early career mode, because the engines are too powerful for the small rockets you're likely to be flying.

[Grunnt]

Yeah, after playing with FAR in 0.90 the atmosphere in 1.0 appeared pretty much absent. This did make the landings very exciting though: it was relatively hard to slow down before impact. But 1.0.2 seems to strike a good balance between the soup and almost-absent-atmosphere, so I would expect it to stay pretty much like this.

[mrclucks]

I was delibertly trying to stay within the prograde marker, the flipping would happen when i couldnt keep prograde even whole holding down the key. I was only going about 600m/s at 20km (generally) but in my hour of trying different launch profiles, I also tried throttling down as well with pretty much no change.

Quick semi side note; I didn't think going too fast would matter anymore than just atmospheric losses of dv. Thank you for that tidbit of information

[EtherDragon]

I was delibertly trying to stay within the prograde marker, the flipping would happen when i couldnt keep prograde even whole holding down the key. I was only going about 600m/s at 20km (generally) but in my hour of trying different launch profiles, I also tried throttling down as well with pretty much no change.

Quick semi side note; I didn't think going too fast would matter anymore than just atmospheric losses of dv. Thank you for that tidbit of information

So, you have a lot of things working against you on a rocket during ascent (assuming no tail-fins).

1. The rocket is already bottom-heavy, i.e. the CoM is closer to the bottom than the top - even on the launch pad.

1b. This makes the nose more top-draggy - the nose has more leverage and there is more drag on the top "half" of the rocket if it starts listing sideways the torque can overwhelm your control.

2. The CoM moves closer to the bottom the longer the rocket burns (especially tall ones) because the fuel drains from top to bottom. As the rocket ascends it becomes more top-draggy over time.

2b. Dumping spend stages can exacerbate this as sometimes these stages help keep your CoM higher.

Edit: to tie this into the original thread - this rocket behavior is not going to drastically change in any upcoming aero updates. Nose-draggy rockets are still going to want to flip over, so you will want to learn how to deal with this behavior no matter what.

Edited May 7, 2015 by EtherDragon

[stevehead]

Tell that to delta heavy. No delta heavy does not use crossfeed as its complicates stuff a lot and TWR is far higher than in KSP anyway reducing the benefit.

My standard heavy launcher uses crossfeeed, 1x2 core with orange tank on top, two orange tanks with mainsail as boosters. yes payload faction and fairing is larger than real world rockets.

The Delta IV Heavy was designed the way it is because it is cheaper to just strap on two Delta common booster cores than to design a completely new rocket with the costs of extra manufacturing and different logistics for transportation and launch preparations... that is why ULA went with a modular design. From a pure fuel economy standpoint, it is more efficient to grow your rocket stages upwards than outwards and only grow outwards if you don't have the hardware to do the former. Every time you add stacks to the side of your main stack, you lose efficiency due to drag. You also have to consider that the Delta IV Heavy boosters themselves have a burn time that almost equates the same time it takes to get into orbit around Kerbin, but the depth of Earth's atmosphere is not that much greater than Kerbin's atmosphere, so the real world Delta IV Heavy boosters have much less drag losses (relatively) overall than a similarly built design in KSP.

I'm not saying to not use a Delta IV Heavy design, I do myself often. Whatever works for you works. I'm just speaking strictly from an efficiency standpoint.

Edit:

Maybe I should have worded the following better regarding rocket designs (was very late for me):

"Tall and sleek, and design your rockets so that any boosters added are for providing extra thrust early on, not as a means to add extra dV unless it's impossible to get more out of your main stack with the hardware you have."

Edited May 7, 2015 by stevehead

[Redshift OTF]

I feel sorry for Squad. They have to make the aero work going up as well as going down. They need to reduce lift a lot in the next update but perhaps only reduce drag for certain parts like wings so re-entry slows crafts as they currently do in 1.0.2

[DeltaB]

My opinion is to go ahead and learn it now. Once you get a feel for how drag forces affect your launch, it's pretty easy to adjust your speed accordingly when they make changes. Learning how to design a ship that can fly through soup will make you a better designer if they nerf the aero (more power, less drag) or it will give you a step in the right direction if they buff it (more lift, more drag).

[magnemoe]

The Delta IV Heavy was designed the way it is because it is cheaper to just strap on two Delta common booster cores than to design a completely new rocket with the costs of extra manufacturing and different logistics for transportation and launch preparations... that is why ULA went with a modular design. From a pure fuel economy standpoint, it is more efficient to grow your rocket stages upwards than outwards and only grow outwards if you don't have the hardware to do the former. Every time you add stacks to the side of your main stack, you lose efficiency due to drag. You also have to consider that the Delta IV Heavy boosters themselves have a burn time that almost equates the same time it takes to get into orbit around Kerbin, but the depth of Earth's atmosphere is not that much greater than Kerbin's atmosphere, so the real world Delta IV Heavy boosters have much less drag losses (relatively) overall than a similarly built design in KSP.

I'm not saying to not use a Delta IV Heavy design, I do myself often. Whatever works for you works. I'm just speaking strictly from an efficiency standpoint.

Edit:

Maybe I should have worded the following better regarding rocket designs (was very late for me):

"Tall and sleek, and design your rockets so that any boosters added are for providing extra thrust early on, not as a means to add extra dV unless it's impossible to get more out of your main stack with the hardware you have."

Yes, i agree, however in my setting the boosters was hidden behind the payload anyway. in two cases 3 x 2.5 m stacks in the base. Nosecones on top of both payload and boosters but plenty of drag from stuff like drills solar panels and legs so I used the old 0.9 launch profile, payload around 40 ton.

The other payload was an MK3 stack with radial mounted LV-N inside faring, here an 3.75 meter stack would probably work better however not sure how it would turn out economical.

[stevehead]

Yes, i agree, however in my setting the boosters was hidden behind the payload anyway.

Well, that's an atypical design when your payload is as wide as the main stack + boosters... very Kerbalish .

[Trenchfoot]

I'm not crossing the street anymore because that last car almost hit me. I'm going to walk around this one little block and whenever I want to see or do something else, I'll remember that last car that almost hit me and sit at my computer and gripe... Just saying.

[Curveball Anders]

I'm not crossing the street anymore because that last car almost hit me. I'm going to walk around this one little block and whenever I want to see or do something else, I'll remember that last car that almost hit me and sit at my computer and gripe... Just saying.

Not that I want to be stressing you out.

But have you tried walking around the block, the other way?

[antbin]

I love spaceplanes, I loved the 1.0 aero, and I'm not going to bother learning 1.0.2. Waiting fingers crossed for the next update to start playing again.

[Trenchfoot]

Not that I want to be stressing you out.

But have you tried walking around the block, the other way?

I just end up here. lol

[Nobody_1707]

I'm not saying it doesn't work, I'm saying its now more efficient to not use it. Every time you shed those boosters, you are losing thrust, and having to spend more time going vertical (gravity loses) and spending more time in the deeper part of atmosphere (more drag). You're better off to use the same design but without asparagus, that way when you drop the boosters, your main stack has a higher TWR than what you would had on the launch pad with full fuel and no boosters (in other words your TWR is always increasing until you get to your second main stack stage); you can punch through the earlier part of the atmosphere quicker while doing a proper gravity turn to get yourself horizontal.

You can actually asparagus stage with only one set of boosters you know, and honestly, the lower thrust after dropping a booster should be made up by the lower mass after dropping a booster. A couple of pairs of asparagus staged boosters hardly cause any drag at all, anyway.