Reentry profiles

[Warzouz]

I did a lot of reentry for testing my SSTO rocket stage. Basically it's a familly of rockets with various number of radial engines partially feeded by the rocket core. The batteries, SAS and probe core are at the bottom of the rocket. I added a heat shield with the right amout of ablator to avoid destruction of this sensitive part.

As you might have suspect I enter atmo bottom/engine first. Air brakes allow me to tune the landing site. Then chutes and little powered landing to avoid breaking something.

On anohter matter I was testing my atmo SSTO 7T lander for Duna and Laythe. I did a quick Hyperedit. The lander is very basic. A small rockamax fuel tank and a Terrier under it. It's not aero dynamic at all. The bottom is flat, no heat shield.

I landed without even burning effect. Surprised, I tested it on Laythe and I landed perfectly (not sure the terrier would make me take-off thought, but that wasn't the point)

Now back to the SSTO stuff. So I tested aligning my SSTO sideways when renetry. And... that went very well. I didn't had any flame effect and even non mach effect. The lower atmo forced me bottom first, but ht speed was already very low to use the chute.

What is you usual renetry approach when you try to land more complex and fragile things than a a pod on a atmo world ?

BTW : solar eclipses on Duna are an issue : don't rely on solar only...

[ftunk70]

I guess it depends on the ballistic coefficient of your craft. A large and light craft will start decelerating higher up in the atmosphere and thus get less heating. The Skylon uses this concept to avoid expensive and heavy heatshields. If your craft is light enough, or slow enough, you won't need a heat shield.

[Warzouz]

My rocket SSTO stages range from 15T to 230T (dry weight) when reentring atmo. They are quite hard to steer.

But the lander is very regular, as you would have seen hundred of times (a landing can on top of a fuel tank and engine at the bottom surrounded by landing struts). The tank is a small rockamax to have a large base for easy landing (avoid tall lander tipping).

Finally it seems that's the easiest way to enter atmo.

Maybe the downside is that drag I gain to slow me down will cost me to take-off...

[ajburges]

If heat management is a concern, use the aero overlay. Your craft will always orient to a local minimum of drag without control input. Drag is always your friend in reentry.

Having the overlay also tells you when and where you get body lift. This keeps you higher (and cooler) longer and gives you several km of cross-range on decent!

You need moderate control elements and beefy batteries to use this, but none of my HKO craft need heat shields or brakes because of this. I only use heat shields for capsules that are write offs (little recovery value) punching in near orthogonal to the surface. (In .90 style)

[cybersol]

I like higher TWR for more optimal deltaV to orbit and for taking less time to get there. In order for my rocket SSTOs to punch through the sound barrier and remain easily flyable, they often have lots of control authority and low control fins. By the time I've optimized them to be stable facing prograde on the way up, they also strongly prefer to re-enter prograde. So after the deorbit burn I face prograde, but then lean into the blunt side of the rocket to control decent rate and fine tune the landing site. With the strong control authority I mentioned before I can almost always control the descent. In the rare case that I do manage to spin out though, it just seems to slow me down faster and I land short of the KSC.

[Foxster]

I tend to stick some air brakes on the top along with 'chutes. I open the air brakes ready as soon as I do my de-orbit burn. These brake the craft through the flames and then I open the 'chutes right after, leaving the air brakes on so they provide drag to help with orientation and further slowing.