At what point abort of space mission is impossible?

[Pawelk198604]

For exemple Soyuz i wonder does is point that they cannot abort even is something bad happening?

[asmi]

Soyuz abort system has 6 different abort modes depending on MET, which cover all the way into orbit.

[PB666]

 

When you see a bright glow in mid-daylight expanding real fast, there is a pretty good chance its too late to abort.

Atlas Centaur V, moments after escape capsule flew off.

Edited May 17, 2016 by PB666

[Gaarst]

They can always abort. But some modes include abort to orbit (Space Shuttle had an ATO) when the spacecraft is fast enough that a failure does not prevent it to get in orbit.

Wikipedia has fairly complete articles on Space Shuttle, Soyuz, Apollo and Orion abort modes if you wish to learn more.

 

That is for manned rockets. For unmanned ones I guess there are less possibilities and they just end up trying to make sure the rocket doesn't crash on someone's house.

Edited May 17, 2016 by Gaarst

[RCgothic]

The Space Shuttle was particularly problematic because the solid rocket boosters couldn't be shut off and would cook anything attempting to get away from the failing boosters. Between booster ignition and booster separation:

• Structural failure of any part, (booster, tank or shuttle) was not survivable.
• Significant booster thrust differential was not survivable.
• Failure of a booster to properly ignite was not survivable.
• One or two main engines out was survivable on condition everything held together until after booster separation.
• Three main engines out was not survivable.

Basically IMO the only business solid rockets have anywhere near manned launches is in the launch-escape system and ullage motors. The sooner they replace the SLS solids with advanced kerolox boosters the better.

Edited May 17, 2016 by RCgothic

[PB666]

10 minutes ago, RCgothic said:

The Space Shuttle was particularly problematic because the solid rocket boosters couldn't be shut off and would cook anything attempting to get away from the failing boosters. Between booster ignition and booster separation:

• Structural failure of any part, (booster, tank or shuttle) was not survivable.
• Significant booster thrust differential was not survivable.
• Failure of a booster failure to ignite was not survivable.
• One or two main engines out was survivable on condition everything held together until after booster separation.
• Three main engines out was not survivable.

Basically IMO the only business solid rockets have anywhere near manned launches is in the launch-escape system and ullage motors. The sooner they replace the SLS solids with advanced kerolox boosters the better.

Shuttles main engine powered up only after boosters reached full power, the shuttle itself did not have enough booster power to lift off, if a single booster failed the shuttle would just sit on the pad until the other burnt out of fuel. With a single engine, two or three engine failure, keep launch clamps power down main engines and wait with clinched fists for 2 minutes, then about thirty minutes for tower cool down, then rescue. 

Of course, once the launch clamps are released the shuttle could no abort if it had a positive rate of climb. 

[asmi]

20 minutes ago, PB666 said:

Shuttles main engine powered up only after boosters reached full power, the shuttle itself did not have enough booster power to lift off, if a single booster failed the shuttle would just sit on the pad until the other burnt out of fuel.

It's the other way around - SSME's were lit before SRBs because one they are lit there's no coming back.

[KSK]

21 minutes ago, PB666 said:

Shuttles main engine powered up only after boosters reached full power, the shuttle itself did not have enough booster power to lift off, if a single booster failed the shuttle would just sit on the pad until the other burnt out of fuel. With a single engine, two or three engine failure, keep launch clamps power down main engines and wait with clinched fists for 2 minutes, then about thirty minutes for tower cool down, then rescue. 

Of course, once the launch clamps are released the shuttle could no abort if it had a positive rate of climb. 

Wrong way round?  I always thought the SSME's lit first, throttled up and then the SRBs lit. Booster ignition was carefully timed for the midpoint of the 'twang', that is, movement of the whole Shuttle stack caused by SSME start.

Edited May 17, 2016 by KSK

[Gaarst]

15 minutes ago, PB666 said:

Shuttles main engine powered up only after boosters reached full power, the shuttle itself did not have enough booster power to lift off, if a single booster failed the shuttle would just sit on the pad until the other burnt out of fuel. With a single engine, two or three engine failure, keep launch clamps power down main engines and wait with clinched fists for 2 minutes, then about thirty minutes for tower cool down, then rescue. 

Of course, once the launch clamps are released the shuttle could no abort if it had a positive rate of climb. 

The SSMEs were ignited a few seconds before the SRBs (causing a RSLS if they did not throttle up as plannned).

Once the SRBs ignited, the shuttle went up. If only one of them ignited or something, then too bad...

[RCgothic]

1 hour ago, PB666 said:

Shuttles main engine powered up only after boosters reached full power, the shuttle itself did not have enough booster power to lift off, if a single booster failed the shuttle would just sit on the pad until the other burnt out of fuel. With a single engine, two or three engine failure, keep launch clamps power down main engines and wait with clinched fists for 2 minutes, then about thirty minutes for tower cool down, then rescue. 

Of course, once the launch clamps are released the shuttle could no abort if it had a positive rate of climb. 

The solid booster fire command isn't given until the SSMEs are verified on, and the hold-down bolts are detonated at the same instant. Once the shuttle's SRBs were ignited, the vehicle was committed to liftoff.

But even so I hesitate to contemplating a full firing of the boosters on the pad whilst strapped to a full tank of hydrogen until the sound suppression system exhausts its 300,000 gallons in just 20s... 

Edited May 17, 2016 by RCgothic

[PB666]

Shuttles thrust is 30,125,000 N and starting mass is 2 050 000 (without payload) this is less than a 1.5 TWR

Each booster contributed 41.5 percent of thrust lift off, if you dropped one engine. 1.5 x (1-0.41) = TWR 0.881

You are not going anywhere with a failed booster. So for 100s seconds you will be experiencing living hell.

 

 

[wumpus]

1 hour ago, RCgothic said:

The Space Shuttle was particularly problematic because the solid rocket boosters couldn't be shut off and would cook anything attempting to get away from the failing boosters. Between booster ignition and booster separation:

• Structural failure of any part, (booster, tank or shuttle) was not survivable.
• Significant booster thrust differential was not survivable.
• Failure of a booster to properly ignite was not survivable.
• One or two main engines out was survivable on condition everything held together until after booster separation.
• Three main engines out was not survivable.

Basically IMO the only business solid rockets have anywhere near manned launches is in the launch-escape system and ullage motors. The sooner they replace the SLS solids with advanced kerolox boosters the better.

There were plenty of plans for aborting launch, but it was known that plenty of them were impossible (for at least some stages of the mission).  I think by the time they simulated all of them it turned out that nearly all were certain death.

Also note the most spectacular recent [unmanned] rocket explosions were kerlox beasts.  Falcon 9 exploded and Antares failed to lift, although I suspect both were survivable with launch-escape systems.  The shuttle's issue was that the escape system (the shuttle itself) was too big to abort a SRB failure.  Of the many issues with SLS, I doubt the SRBs will be a huge issue (unless they completely fail to build a working escape system).

[Gaarst]

11 minutes ago, PB666 said:

Shuttles thrust is 30,125,000 N and starting mass is 2 050 000 (without payload) this is less than a 1.5 TWR

Each booster contributed 41.5 percent of thrust lift off, if you dropped one engine. 1.5 x (1-0.41) = TWR 0.881

You are not going anywhere with a failed booster. So for 100s seconds you will be experiencing living hell.

 

 

Sitting on a 2000t stack of highly explosive material sitting on two loose (remember that the bolts that secure the SRBs are detonated at the moment of ignition) firing solid rocket booster will get you somewhere... you are not coming back from that place though.

Also, 0.881 TWR for the whole stack will not lift off. 1.762 TWR on one side and 0 on the other will make the whole thing move around uncontrollably eventually leading to its demise in the course of a few seconds.

 

Also, citing NASA's Crew Operation Manual:

Quote

A shuttle launch may be scrubbed or aborted up to solid rocket booster (SRB) ignition.

 

[PB666]

6 minutes ago, Gaarst said:

Sitting on a 2000t stack of highly explosive material sitting on two loose (remember that the bolts that secure the SRBs are detonated at the moment of ignition) firing solid rocket booster will get you somewhere... you are not coming back from that place though.

Also, 0.881 TWR for the whole stack will not lift off. 1.762 TWR on one side and 0 on the other will make the whole thing move around uncontrollably eventually leading to its demise in the course of a few seconds.

 

Also, citing NASA's Crew Operation Manual:

 

Note the main engines would have gone offline, and you would only have a stack TWR of 0.615. Side TWR is slightly above G-force,

Of course you can't abort after SFRB ignition, you can however release the SFRB, lol.

 

Edited May 17, 2016 by PB666

[Gaarst]

2 minutes ago, PB666 said:

Note the main engines would have gone offline, and you would only have a stack TWR of 0.615. TWR our slightly above G-force,

Of course you can't abort after SFRB ignition, you can however release the SFRB, lol.

 

Still, that's a TWR above 1 so the thing is exploding.

And I don't think that just letting the booster go is a good idea (apart from the exhaust being headed straight at you, remember that the shuttle literally sits on the boosters)  Though I didn't read anything about that, should probably ask NASA to be sure

Edited May 17, 2016 by Gaarst
Forgetting words n stuff

[PB666]

1 minute ago, Gaarst said:

Still, that's a TWR above 1 so the thing is exploding.

And I don't think that just letting the booster go is a good idea (apart from the exhaust being headed straight at you, remember that the shuttle literally sits on the boosters)  Though I didn't read anything about that, should probably ask NASA to be sure

No the Main tank clamps can hold the booster at least while the booster is near full fuel, once the fuel goes down then the forces might be to great for the decoupler,  you have to release the booster, you can use the main engines to buffer the fall if you power them up as the boosters are being decoupled. Of course the red tank will fall over once you hit the pad, but a little bit of hydrol-ox never hurt anyone, cept maybe challenger, and my high school chemistry class mates . . . . . .

BTW when has an SFRB ever failed to ignite on a launch? I though that was just about the most reliably firing engine that has ever existed. Just have two primer cords on the sucker and it goes.

We are after all talking about the shuttle in the past tense, so it kind of means that the risk is something that might have showed up in the past.

 

 

[sevenperforce]

Did the OMS have enough thrust to push the Shuttle clear of the launch stack if the tank and SRBs were jettisoned?

[Gaarst]

3 minutes ago, sevenperforce said:

Did the OMS have enough thrust to push the Shuttle clear of the launch stack if the tank and SRBs were jettisoned?

No.

In real life most upper stages or manoeuvring systems have really low thrusts and small correction burns last several minutes. (The shuttle's OMS had about 50kN thrust)

[sevenperforce]

1 minute ago, Gaarst said:

No.

In real life most upper stages or manoeuvring systems have really low thrusts and small correction burns last several minutes. (The shuttle's OMS had about 50kN thrust)

Too bad. It performed the actual orbital insertion to circularize, so I thought it might have more kick.

[DDE]

On ‎17‎.‎05‎.‎2016 at 8:43 PM, Gaarst said:

That is for manned rockets. For unmanned ones I guess there are less possibilities and they just end up trying to make sure the rocket doesn't crash on someone's house.

It's called "Range Safety". In the US it's a self-destruct. In Russia it's aiming to crash in the Kazakh or Siberian steppe.

On ‎18‎.‎05‎.‎2016 at 1:15 AM, sevenperforce said:

Too bad. It performed the actual orbital insertion to circularize, so I thought it might have more kick.

Well, it has a dV of 300 m/s, but it has no more blast than the Terrier.

The Soviets created the LES for the Buran based on a small dedicated SRB, despite have an OMS-like system where the Shuttle had SSMEs.