Space X Mark 3 Parachute

[farmerben]

 

Elon says the Mark 3 parachute is probably ten times safer than the Mark 2. 

I observe that the Mark 3 has more perforated, feathered fabric at on the sides than any other parachute.  It seems to spend more time in the half-deployed configuration than standard.  The transition to full deployment is extremely precise.  Typically this would be done with a slip ring or some other mechanical release, but I'm wondering if it different in this case.  This is just a guess, but I think the perforated sides keep the chute half-deployed at high speed, and the full opening mechanism is purely a function of air speed.  

I've always wondered about the possibility of using some sort of enhanced aerobrake at higher altitudes and speeds.  

It seems like a wind-sock, ribbon, or kite could survive better in the wake of a capsule... just as thermal blankets survive on the upper surfaces of the vessel.  But this might be such a trivial amount of drag as to not be worth it.  The key thing is transfer the energy to the atmosphere, and that basically means creating a bigger bow shock.   So it seems like the key technology is extendable aerobrake parts like we have in KSP.   One way to implement this is to make them burn in a controlled manner, rather than explode.  A tapered piece of wood would perform wonderfully, disintegrating from tip to base.  In thin atmosphere it does not really burn, it out gasses and becomes charcoal which flakes away.  

 

 

 

 

 

[sevenperforce]

With all the problems with these parachutes, I can see why SpaceX wanted to land on SuperDracos.....

[έķ νίĻĻάίή]

Agreed

[kerbiloid]

56 minutes ago, farmerben said:

Elon says the Mark 3 parachute is probably ten times safer than the Mark 2. 

In other words, the Mark 2 was ten times unsafer than Mark 3.

But why were they upgrading it to Mark 3 if Mark 2 was enough safe?

P.S.

Spoiler

"Look, we have better chutes than the Boeing has, lol!"

 

Edited November 18, 2019 by kerbiloid

[sevenperforce]

The probability of LOCV is the reciprocal sum of failure probabilities for all landing modes. So adding any backup mode decreases the probability of LOCV as long as that mode's existence doesn't increase the risk of abort conditions being met.

[Geonovast]

Makes you wonder if the superdracos could still be used in the event of multiple chute failures.

[sevenperforce]

21 minutes ago, Geonovast said:

Makes you wonder if the superdracos could still be used in the event of multiple chute failures.

Not any more. After the capsule explosion, the SuperDraco valves were replaced with burst discs, so they are now single-use.

Although I suppose they could still be used for chute failure in a nominal landing situation, though not post-abort.

[Geonovast]

6 minutes ago, sevenperforce said:

Not any more. After the capsule explosion, the SuperDraco valves were replaced with burst discs, so they are now single-use.

Although I suppose they could still be used for chute failure in a nominal landing situation, though not post-abort.

Yeah that was my thought.  Even if it's not rated to land the capsule, I'd rather have an off-chance landing with high possibility of injury than an almost guaranteed fatal crashing.

[RealKerbal3x]

10 minutes ago, sevenperforce said:

Although I suppose they could still be used for chute failure in a nominal landing situation, though not post-abort.

I believe this was their original plan, back when they wanted to use the SuperDracos for landing. On a normal mission, the engines would be used for propulsive landing, but in the event of an abort (since all of the fuel that otherwise would have been used for landing would have been depleted by the abort burn) they would use parachutes to land in the ocean.

Edited November 18, 2019 by RealKerbal3x

[sevenperforce]

41 minutes ago, Geonovast said:

Yeah that was my thought.  Even if it's not rated to land the capsule, I'd rather have an off-chance landing with high possibility of injury than an almost guaranteed fatal crashing.

At one point, after propulsive landing was canceled but before the capsule failure, I believe Hans or someone said that the programming for propulsive landing was still in there and could be activated in the event of a chute failure. But given the burst disc changes that seems unlikely to remain.

[StrandedonEarth]

3 hours ago, sevenperforce said:

Not any more. After the capsule explosion, the SuperDraco valves were replaced with burst discs, so they are now single-use.

I thought those valves/burst disks were just to pressurize/arm the system, but the actual engine control valves were further downstream?

[sevenperforce]

1 hour ago, StrandedonEarth said:

I thought those valves/burst disks were just to pressurize/arm the system, but the actual engine control valves were further downstream?

It's my understanding that once you fire the SuperDracos once, you can't fire anything else until you replace the check valves. But I could be wrong.

[magnemoe]

13 hours ago, sevenperforce said:

It's my understanding that once you fire the SuperDracos once, you can't fire anything else until you replace the check valves. But I could be wrong.

With an powered landing you would just do one burn anyway. However in an abort you will burn the tanks dry or almost dry and burn at practically full trust and its possible they have simplified the system for abort only. 

[kerbiloid]

On 11/18/2019 at 7:11 PM, RealKerbal3x said:

but in the event of an abort (since all of the fuel that otherwise would have been used for landing would have been depleted by the abort burn) they would use parachutes to land

...where the roulette stops.

On 11/18/2019 at 7:00 PM, sevenperforce said:

After the capsule explosion, the SuperDraco valves were replaced with burst discs, so they are now single-use.

So, the single-use engines are now an overweight of the capsule and its landing system.

A year ago I was suggesting "them" here to just add the crew seats into the Cargo Dragon instead of continuing with the Crew Dragon technothriller.
And was asked why such weird idea.

Exactly because. A single-use engine should be in the expendable trunk aka service module.

Now every flight of a Crew Dragon is devoted to bringing back from orbit a barrel of wastes and the metal scrap aka engines.

5 hours ago, magnemoe said:

With an powered landing you would just do one burn anyway. However in an abort you will burn the tanks dry or almost dry and burn at practically full trust and its possible they have simplified the system for abort only. 

A backup set of chutes would anyway lighter than a fuel tank and the engine octopack.
And usually they need just a triple chute. If one fails, two are still opened.

P.S.
I bet on CST.

Edited November 19, 2019 by kerbiloid

[sevenperforce]

Just now, kerbiloid said:

So, the single-use engines are now an overweight of the capsule and its landing system.

The engines themselves are not single use, but the engines can only be used once per flight. Once brought back, the engines are certainly still good for use on a subsequent flight.

Just now, kerbiloid said:

A backup set of chutes would anyway lighter than a fuel tank and the engine octopack.

The fuel tank and propellants double for RCS/OMS so it's not a waste. The engines are not terribly heavy.

[kerbiloid]

1 minute ago, sevenperforce said:

The engines themselves are not single use, but the engines can only be used once per flight.

On which event?

[sevenperforce]

Just now, kerbiloid said:

On which event?

Even in the original conception, where Crew Dragon was to use the engines nominally for landing with chutes as backup, Crew Dragon would never have used its SuperDracos more than once per flight. Firing the SuperDracos for abort would expend so much propellant that the chutes would be required for post-abort splashdown.

It is my understanding that once the burst disc is ruptured, the engines will only fire once, after which the burst disc must be replaced. The engines can of course be throttled and even turned off after that point. The engines are hot-fired before each launch anyway, with the burst disc being replaced between hot-fire and launch.

[kerbiloid]

20 minutes ago, sevenperforce said:

Even in the original conception, where Crew Dragon was to use the engines nominally for landing with chutes as backup, Crew Dragon would never have used its SuperDracos more than once per flight. Firing the SuperDracos for abort would expend so much propellant that the chutes would be required for post-abort splashdown.

So, why not just use an expendable external solid fuel motor for abort/deorbit (both ~300 m/s) and separate from it a tiny internal solid motor for soft landing?
Why eight liquid-fuel full-featured engines and a whole tank of highly flammable and toxic propellant inside the crewed capsule and why refurbish it every flight?

Upd.
Btw, don't its RCS thrusters spend fuel from the same tank while in orbit?
So, on landing unlikely it can have some precise amount of remaining propellant, so as well delta-V. Either insufficient (then oops), or excessive (then it lands with a barrel of explosive poison against the crew heads).

Edited November 19, 2019 by kerbiloid

[sevenperforce]

14 minutes ago, kerbiloid said:

So, why not just use an expendable external solid fuel motor for abort/deorbit (both ~300 m/s) and separate from it a tiny internal solid motor for soft landing?
Why eight liquid-fuel full-featured engines and a whole tank of highly flammable and toxic propellant inside the crewed capsule and why refurbish it every flight?

The requirements for an abort motor and deorbit motor may reflect similar dV, but they otherwise could not be more dissimilar. An abort motor needs high thrust and low precision; a deorbit motor needs low thrust and high precision. While it is theoretically possible to design a solid motor which would have both high-thrust and low-thrust modes, such complexity would not be ideal for something mission-critical as an abort engine. If this were KSP, one could imagine an array of small solid motors which would fire concurrently on abort but sequentially on deorbit; however, real-life solid motors have thrust fluctuations which make this infeasible. Strap-on SRBs typically need inclined nozzles for this specific reason, despite the cosine losses they incur; the STS SRBs used the largest TVC ever designed to accommodate this.

Unless a solid motor is used to brake just before touchdown under parachutes, as with Soyuz or New Shepard, it is wholly unsuitable for soft landing. Computers may be very good at suicide burns but they still must throttle.

Moreover, the need for propellant inside the capsule comes from the need for the capsule to maneuver on orbit. Cargo Dragon has already been reusing its propellant tanks and Draco thrusters for OMS, rendezvous with the ISS, and so forth for ages.

[kerbiloid]

45 minutes ago, sevenperforce said:

The requirements for an abort motor and deorbit motor may reflect similar dV, but they otherwise could not be more dissimilar.

~1..2 km to jump from ground to let the chutes open.
~250 m/s to deorbit from 500 km, and unlikely it can ever get higher.
So, 300 m/s is more or less universal.

Another benefit: they can't spend fuel required for return.

Also, solid motors are just more reliable.
And liquid motors are either complex (pump-fed) or require a high-pressure tank of explosive poison (pressuire-fed).

45 minutes ago, sevenperforce said:

An abort motor needs high thrust and low precision; a deorbit motor needs low thrust and high precision.

They can split the powder in several cans at the single chamber, and ignite them either all at once (to abort) or one by one (to deorbit).
That's enough accurate for the chute landing.

45 minutes ago, sevenperforce said:

Unless a solid motor is used to brake just before touchdown under parachutes, as with Soyuz or New Shepard, it is wholly unsuitable for soft landing

If land without chutes and start ignite at 2 km altitude.
If land even by drogue chutes they have to ignite it just at 20 m altitude at 20 m/s vertical speed and next-to-zero horizontal (because the drogues are small and are bad sails).
Then all they need is to ignite them a second before touchdown to hover at 2 m and softly land.

(That's more or less PTKNP way of landing).

45 minutes ago, sevenperforce said:

Moreover, the need for propellant inside the capsule comes from the need for the capsule to maneuver on orbit.

Where are Soyuz RCS thrusters?

***
And what can stop from moving all deadly things, as well as engines, RCS, electricity, etc, into a small service capsule, maybe derived from same Dragon one.
Also communication, navigation, i.e. everything but abort, landing, and backup radio.

Then they have all significant systems reusable, safely land the crew, and just have to land two capsules: crew and service.
The only expendable thing is the solid motor below the capsule (consisting of fuel and a steel envelope) and a truss to attach the service capsule from below.
It will look like a bee: head of crew, chest of solid motor and truss, stomach of propulsion. The chest is expendable, everything other is reusable. They anyway spend the heavier trunk.

Also the service capsule can be a multifunctional reusable tug for expendable cargo ships or station modules.
Also by adding an expendable fuel tank (maybe with additional RCS) in between (inside/instead the truss), it can vary the orbital delta-V for different missions.

Edited November 19, 2019 by kerbiloid

[sevenperforce]

On 11/19/2019 at 12:25 PM, kerbiloid said:

Also, solid motors are just more reliable.
And liquid motors are either complex (pump-fed) or require a high-pressure tank of explosive poison (pressuire-fed).

Sometimes solids are more reliable. To date, the only engine-related human fatalities have been the result of a solid rocket motor failure. 

Small nitpick here, but the distinction you're drawing (complex, pump-fed, non-hypergol vs simple, pressure-fed hypergol) is inaccurate. You can have pressure-fed cryo engines (Kestrel, Xodiac, Tronador T10, Aerospike Annular J-2, RS-17, RM-1500) and you can have pump-fed hypergol engines (RD-253, LR-87-11, YF-20, RD-215, Gamma-8, and many others). We often see pressure-fed cycles combined with hypergolic propellants because hypergols need no ignition system, which makes them more reliable. Pressure-fed cycles are favored when either high reliability or low propellant volume is involved.

Quote

They can split the powder in several cans at the single chamber, and ignite them either all at once (to abort) or one by one (to deorbit).
That's enough accurate for the chute landing.

It is not enough, not for abort and certainly not for landing. We can do that in KSP, because all solid motors have identical firing characteristics and can be perfectly aligned, but clustering solids in real life is not a good idea. Rockets with solid boosters strapped to the first stage (Atlas V, Vulcan, Delta IV Medium) use nozzle deflection, where the nozzles are canted away from the rocket body to fire through the center of mass:

This is used regardless of whether even or odd numbers of boosters are installed. As I said before, the STS used the largest TVC system ever built to solve this problem of inconsistent thrust on the Shuttle SRBs.

The only time I know of when a great number of solid motors have been clustered in parallel (like Sepratrons) was in the second stage of the Jupiter-C:

This rocket used eleven scaled-down Sergeant missile motors which fired simultaneously for six seconds, after which the core popped out and fired its own internal motor. These motors did not have canted nozzles, but instead used an electric gyrostabilizer inside the payload spinning between 450 and 750 rpm to accommodate for thrust variations.

Quote

On 11/19/2019 at 12:13 PM, sevenperforce said:

Unless a solid motor is used to brake just before touchdown under parachutes, as with Soyuz or New Shepard, it is wholly unsuitable for soft landing.

If land without chutes and start ignite at 2 km altitude.

No astronaut in her right mind would ever climb aboard a capsule with a solid landing motor and no chutes. A hyrid motor, maybe. But never, ever a solid. Using a solid motor for landing really puts the "suicide" in suicide burn.

Quote

If land even by drogue chutes they have to ignite it just at 20 m altitude at 20 m/s vertical speed and next-to-zero horizontal (because the drogues are small and are bad sails).
Then all they need is to ignite them a second before touchdown to hover at 2 m and softly land.

(That's more or less PTKNP way of landing).

Nothing wrong with using solids to brake at chuted-landing touchdown. That's how Soyuz does it and that's how New Shepard does it. Starliner uses airbags to perform the same function.

Quote

Where are Soyuz RCS thrusters?

Service module.

Quote

And what can stop from moving all deadly things, as well as engines, RCS, electricity, etc, into a small service capsule, maybe derived from same Dragon one.
Also communication, navigation, i.e. everything but abort, landing, and backup radio.

Then they have all significant systems reusable, safely land the crew, and just have to land two capsules: crew and service.
The only expendable thing is the solid motor below the capsule (consisting of fuel and a steel envelope) and a truss to attach the service capsule from below.
It will look like a bee: head of crew, chest of solid motor and truss, stomach of propulsion. The chest is expendable, everything other is reusable. They anyway spend the heavier trunk.

Two heat shields? No, no, definitely no.

And the trunk is not "heavier" by any stretch. It is very lightweight, and it allows both Dragon vehicles to co-manifest unpressurized cargo.

[kerbiloid]

57 minutes ago, sevenperforce said:

To date, the only engine-related human fatalities have been the result of a solid rocket motor failure. 

To date, all successful mission aborts have been the result of a solid rocket motor successful usage.
As well, all successful seat ejections were.

57 minutes ago, sevenperforce said:

Quote

They can split the powder in several cans at the single chamber, and ignite them either all at once (to abort) or one by one (to deorbit).
That's enough accurate for the chute landing.

It is not enough, not for abort and certainly not for landing. We can do that in KSP, because all solid motors have identical firing characteristics and can be perfectly aligned, but clustering solids in real life is not a good idea.

A 200 t heavy ICBM gets pushed from a silo with iirc three sequential powder cans burn.
I guess, it's enough good for a 10 t capsule pushing as well.

57 minutes ago, sevenperforce said:

Rockets with solid boosters strapped to the first stage (Atlas V, Vulcan, Delta IV Medium) use nozzle deflection, where the nozzles are canted away from the rocket body to fire through the center of mass:

Spoiler

No rocket packs or separatrons. A ring pipe of the chamber, nozzles attached to it where they're needed, powder cans.

The same but bigger as the abort/deorbit propulsor. ~3 m wide, < 1 m thick cylinder under the capsule.

57 minutes ago, sevenperforce said:

No astronaut in her right mind would ever climb aboard a capsule with a solid landing motor and no chutes.

Who said "no chutes"?
You can read: "drogue chutes", 20 m/s landing speed = 72 km/h or 40..50 (?) mph.
A speed of a car if the landing engine fails, but with legs and seat pistons providing 1 m of braking distance, so 20 g of acceleration on hard landing.
Safer than a car crash if the engine fails.

Also, about 500 astronauts have climbed aboard a cabin with no chutes, abort motors, or ejection seats at all.

57 minutes ago, sevenperforce said:

Service module.

I.e. in the rear half of the ship, all of them.
If make a bicapsule ship, they will be placed there as well, but in a reusable unmanned rear capsule.

57 minutes ago, sevenperforce said:

Two heat shields? No, no, definitely no.

When I say that Dragon is overmassed due to its enormous octopack motors and fuel tank inside the heat-proof capsule, they say that Falcon anyway can lift more.
So, that's this more but on purpose.
Put a weak orbital engine into the rear capsule, and move the excessive heat protection from the crew capsule to it, instead of octosuperdraco.

Edited November 21, 2019 by kerbiloid

[Brotoro]

3 hours ago, kerbiloid said:

To date, all successful mission aborts have been the result of a solid rocket motor successful usage.
As well, all successful seat ejections were.

...Except for STS-51-F that made an Abort to Orbit using the SSMEs.

[kerbiloid]

6 hours ago, Brotoro said:

Except for STS-51-F that made an Abort to Orbit using the SSMEs.

It was not an emergency engine usage, it was an engine shutdown.

[Meecrob]

Before Falcon 9, only solid boosters were refurbished. Does that make it foolish to refurbish liquid Falcon 9 boosters currently?