Ram vs. shock cone intake?

[VBlackshadow]

Which one is better for an SSTO? The shock cone unlocks at a higher tech level, so I'd think there must be some advantage to it, but the ram intakes in-game listed stats are better. Is there something to the shock cone I'm missing?

Edited May 6, 2015 by VBlackshadow

[eddiew]

Good question! I would rather like to know this too. I've been using RAM intakes and found them good enough - when they're supported by a structural or similar secondary intake. One RAM per engine has a habit of giving me asymmetric flameouts, which are annoying :/

[Michaelo90]

At least when i tested them in 1.0.0, the shock cone was less draggy than the ram intake, which meant you could fly faster. And one shock cone per rapier is enough so the bigger area of the ram intake doesn't matter.

I haven't tested with the new aero values in 1.0.1/1.0.2 though.

[NathanKell]

Ramp intakes are lighter and have more intake area

Shock cones are heavier but have less drag and survive the heat much, much, much better.

[VBlackshadow]

Thanks for the answers!

I went ahead and made... basically an uncontrolled missile, two rapiers and two precoolers attached to each other with a ram intake on the right side and a shock cone on the left, (and the infinite fuel cheat on) and it veered to the right every launch but both intakes overheated at the same time, so it seems like the drag difference is pretty drastic but the heat survivability not so much. The drag should really be listed in the editor like with the other parts...

[A_name]

Thanks for the answers!

I went ahead and made... basically an uncontrolled missile, two rapiers and two precoolers attached to each other with a ram intake on the right side and a shock cone on the left, (and the infinite fuel cheat on) and it veered to the right every launch but both intakes overheated at the same time, so it seems like the drag difference is pretty drastic but the heat survivability not so much. The drag should really be listed in the editor like with the other parts...

Good experiment!

[DCWarHound]

I'm still learning how to make an SSTO (can only get to orbit with around 50 deltaV left)

What works for me is 2x precoolers and 1x shockcone for every 2x turbojets,so 4x turbojets is 4x precoolers and 2x shockcones.

[Feradose]

Thanks for the answers!

I went ahead and made... basically an uncontrolled missile, two rapiers and two precoolers attached to each other with a ram intake on the right side and a shock cone on the left, (and the infinite fuel cheat on) and it veered to the right every launch but both intakes overheated at the same time, so it seems like the drag difference is pretty drastic but the heat survivability not so much. The drag should really be listed in the editor like with the other parts...

Your experiment seems off. The intakes dont really have the same mass do they? Its reasonable for them to veer off. Try using monopropellant ballast in a cargo bay/service compartment which is in the middle, and align CoM with CoT to get better drag results?

[Starhawk]

Your experiment seems off. The intakes dont really have the same mass do they? Its reasonable for them to veer off. Try using monopropellant ballast in a cargo bay/service compartment which is in the middle, and align CoM with CoT to get better drag results?

The drag difference between the intakes is much more significant in my experience than the 15 kg difference in their mass. I've found the shock cone to be superior for this reason. YMMV.

Happy landings!

[A_name]

The drag difference between the intakes is much more significant in my experience than the 15 kg difference in their mass. I've found the shock cone to be superior for this reason. YMMV.

Happy landings!

I would say that regardless of what variable is actually causing the veering, the bottom line is that one performs better than the other, whether its because of its mass, its drag, or both. Is this reasoning flawed?

[Starhawk]

I would say that regardless of what variable is actually causing the veering, the bottom line is that one performs better than the other, whether its because of its mass, its drag, or both. Is this reasoning flawed?

In fact, the experiment shows that the shock cone intake performs much better. Since the shock cone is heavier, that would tend to offset the veering effect. If they were the same mass the effect would be even more pronounced.

Happy landings!

[A_name]

In fact, the experiment shows that the shock cone intake performs much better. Since the shock cone is heavier, that would tend to offset the veering effect. If they were the same mass the effect would be even more pronounced.

Happy landings!

My thoughts exactly. Thanks for the input!

[Jaffa Cookie]

Ram is better in my opion. however it's not as aerodynamic...????

[worir4]

I would recommend you just use the one that looks the best on your craft.

[RCgothic]

Ram is better in my opion. however it's not as aerodynamic...????

Air gathered is proportion to the volume swept by the intake per second (intake area * speed).

The ram does provide more intake area per unit mass, but as it's draggier you won't be going as fast.

The shock-cone therefore makes up for its reduced area by increased speed.

Speed is crucial to SSTOs. Mass is less important. The shock cone is therefore superior.

[Mister Dilsby]

Speed is crucial to SSTOs. Mass is less important. The shock cone is therefore superior.

Indeed, but turboramjet SSTOs will top out around 1200 m/s, slower than a ship with RAPIERS--is that fast enough for the extra mass of the shock cone to be worth it? I wonder at what top speed the shock cone breaks even/surpasses the ram intake.

[ajburges]

Indeed, but turboramjet SSTOs will top out around 1200 m/s, slower than a ship with RAPIERS--is that fast enough for the extra mass of the shock cone to be worth it? I wonder at what top speed the shock cone breaks even/surpasses the ram intake.

Drag is compounded by time it takes to accelerate.

The experiments support shock cones being better for atmospheric flight. The mass profile suggests the ram intake is better for orbital maneuvering.

I suspect the differences come out in the wash. The most significant drag barrier for space planes is transonic. Once you pass that, more streamlining others minimal velocity gains; flight profile is more important. OTOH the mass difference will only come out to 1% dV difference in the worst scenario. Landing fuel probably has a bigger impact on OMS capability.

For a LKO limited space plane, the shock cones are a no brainer. For an interplanetary space plane, it depends on how often you plan to visit atmospheric worlds. Regardless, both are perfectly serviceable.

[locustgate]

At least when i tested them in 1.0.0, the shock cone was less draggy than the ram intake, which meant you could fly faster. And one shock cone per rapier is enough so the bigger area of the ram intake doesn't matter.

I haven't tested with the new aero values in 1.0.1/1.0.2 though.

Wait so 1 shock cone is enough for a rapier at high alt?