How to make sure parachute does not get destroyed

[AlexZ]

So I'm in the early days of career mode and I'm trying to leave the atmosphere and then return to Kerbal in 1 piece. Not orbit (I'm not far along the tech tree enough to succesfully do that) just fly up to 70km and then land. My approach so far has been to fly straight up, detach my engines, wait until I start falling back down. So far so good. My problem is that every time, my parachute gets destroyed. When it's in half-deployed mode, I'm still accelerating (at this point, my ship is just the basic command module, a science module and the parachute, nothing else) and eventually, I get the message that says the parachute got destroyed. (if I fly too high, by the time the parachute can be opened at all, it's too late, I'm falling too far) How do I decelerate enough in order to make sure my parachute does not get destroyed? Remember, I'm really low on the tech tree.

EDIT: Thanks all. Yes, drag slows me down enough to open my parachute between 2km and 4km above average sea level.

Edited September 27, 2015 by AlexZ

[diomedea]

Believe the concept of "terminal velocity" is what you need: Vt = sqrt( 2*m*g /(ÃÂ*A*Cd)).

As the vessel sinks in the atmosphere, it encounters air with greater density (ÃÂ). Unless the ratio of mass/projected area (m/A) of the vessel is too high, or the whole atmosphere is not dense enough compared to gravity (g) (e.g. Duna), it will slow down enough due to increasing air density for a safe chute opening (in the range of 250 m/s). Keep open the chute window (right-clicking on it) to read if is safe to open or not, when speed is down enough it will show safe and your chute won't get destroyed.

[The_Rocketeer]

The big problem is that since the aero overhaul, small crafts falling vertically just aren't slowed down enough to reach safe deployment speeds.

There are two main solutions:

Slow down by other means first, like braking thrust or airbrakes/flaps. This is probably easier because you only need an extra tank or a few steerable flaps.

or

Change to a curved flightpath so you have a lot longer to slow down.For this to work with small rockets, you need a trajectory that will come down about 1/4 of the way around the planet.

Another thing to try is throwing the steering around wildly and forcing your craft to present a bigger drag profile - the rocket will settle into a state of least resistance, so any steering or tumbling will increase drag and slow you down more.

[Slam_Jones]

The easiest way to tell is to right click the part. There will be a line at the bottom of the infobox that tells you if it is Unsafe/Risky/Safe to open the chute.

[Snark]

Aerodynamic steering can work pretty well even without flaps, for small craft. For example, consider this basic reentry vehicle:

1. Mk1 command pod

2. Mk16 parachute on top

3. 2-ton fuel tank beneath it

4. Terrier engine on the bottom.

...If I fly that on a reasonably-curved trajectory (not falling straight down), and keep it pointed retrograde (i.e. engine-first), and use the command pod's torque to try to point the nose groundwards (i.e. it's flying butt-first, with the engine a bit high and the pod a bit low), it generates enough lift that I can slow down to safe parachute speeds (under 250 m/s) when it's still way high, like well over 10km, and flying mostly horizontally. Works surprisingly well.

[diomedea]

A lot of work was done to properly balance drag and the atmospheric properties for KSP 1.0 (and improved for 1.0.4), to ensure a successful slowdown with command pods. Just rechecked, and can confirm it still works, a Mk-1 pod + mk16 chute reentering vertically from 100 Km altitude, by itself stabilizes with the bottom down and slows to a safe speed at about 3000 m ASL, good for opening chute and slowing to safe descent speed 500 m ASL. About exactly the parameters by design.

However, tested again attaching the science module at the bottom of the Mk-1 pod (what I believe is the configuration in the OP). The science module is very light (0.2 tons) compared to the pod (0.84 tons), however has a larger shape and therefore drag cube: it exerts more drag and that is enough to make the vessel sink nose-down. My test showed the nose-down vessel couldn't slow enough when reentering vertically from 100 Km, and that's certainly due to the lower Cd in the Vt equation. Sorry, but that vessel configuration doesn't allow a safe reentry.

The drag coefficient (Cd) of the pod changes with attitude, tip Cd of a conical shape ~ 0.5 while tail Cd is ~ 1 (actual Cd also changes with Mach speed, Reynolds number). As others suggested, changing attitude to present a wider area (A) to the flow works to slow down more, and that also gives a larger Cd. In my very early career flights when very few parts are unlocked, I use basic fins on the sides of crafts, perfectly balanced to achieve neutral stability, and steer the vessel to present those fins to the flow and increase the area and therefore drag: works very well.

[FyunchClick]

There's a pretty nice mod that colors the background of the parachute icon in the staging list to indicate if it's safe.

[Highguard]

So I'm in the early days of career mode and I'm trying to leave the atmosphere and then return to Kerbal in 1 piece. Not orbit (I'm not far along the tech tree enough to succesfully do that) just fly up to 70km and then land.

Your first 'flight' - not leaving the launchpad - should give you enough science to unlock 'basic rocketry' and 'engineering 101' - which you seem to have as you are using the SC-9001. Almost any second launch will then let you get 'general rocketry'. With the T-45 engine and larger fuel tank* that provides you can easily build a SSTO rocket that reaches orbit and returns the capsule. Hint: take the right contracts and you can get enough money from this that you can switch back to KSC once the rocket is in orbit and upgrade the astronaut's complex. This allows you to EVA your pilot in space for lots more science (and contracts, maybe) before you return the capsule.

[*The larger fuel-tank is useful because it makes the rocket less wobbly, but it isn't strictly necessary. Similarly, the gimballing on the T-45 makes launch much easier but you might be able to manage with just the T-30 if your steering is good enough.]