Jump to content

SRBs, LESs, Ejection Seats & 100% Oxygen Atmosphere (split from SpaceX Discussion)


Recommended Posts

ISS uses a standard nitrox mix at sea level pressures, or pretty close to it.

 

Atlas SRBs are indeed monolithic. I was lucky enough to see a casing being wound more than a decade ago, and it was a continuous composite layup. They're about as big as one can build a monolithic solid motor and still have them road transportable... 5 feet in diameter, 60 feet long, and somewhere around 120000 pounds fully loaded.

Link to comment
Share on other sites

1 hour ago, Starman4308 said:

Does oxygen absorb significantly into things like fabric? I'd imagine the local partial O2 pressure would drop tremendously in the seconds after ejection, going from 1 atm to local atmospheric conditions (potentially very low in upper atmosphere).

Though Oxygen will permeate into fabric like any gas can, it won't chemically stick in fabrics like water vapors can. That said, I'm sure it'd take its sweet time diffusing out on the timescales of an RUD!

Separately, one of the big issues for flammability isn't just that the Oxygen partial pressure would be higher, but also that the lack of Nitrogen. Nitrogen acts as a 'diluent' gas and helps to keep things cool as they try to ignite, effectively snubbing out most tiny fires before they can start. It also lowers the temperature of fires that do arise, and helps keep them from becoming more exciting than the rest of what would be hapening. Having 50% more oxygen in the air is certainly the greater effect (I read 5psi or ~1/3 bar was the plan for Apollo), but the Nitrogen we add plays its part as well!

 

 

Link to comment
Share on other sites

On 2/25/2019 at 3:13 PM, Racescort666 said:

When I was at the Air Force Space and Missile museum at Cape Canaveral, the guy working there was telling us stories about working on the early Atlas program and how they had one launch where the missile never initiated it's pitch maneuver. They activated the flight termination and he said it looked like sparkly confetti up there in the sky. He said, "then we realized that it was directly above us and we should probably get inside before any of those pretty pieces come down because they're basically slivers of razor sharp stainless steel."

Thin metal plates would not fall very fast because of high air resistance and low mass. 
Engine parts and other heavy stuff is more dangerous. 

Link to comment
Share on other sites

Iirc, the Gemini ejections seats were being designed to eject on launchpad and ascent.
Iirc, the designer had studied the archive videos of rocket explosions frame-by-frame, measuring the fireballs expansion with a ruler.
After that he calculated a safe distance for Titan II explosion and followed this value when designing the seats.

(Can't find the prooflink, but there was a b&w chart of fireballs size and pictures of seat with chutes).

20 hours ago, Jacke said:

Of the spacecraft that have been designed with ejection seats (Vostok, Gemini, the initial Shuttle flights), all we know for sure is that the Vostok seat works on recovery.

There were also five ejection seat tests on Progresses-38..42.
The seats were installed on top of the shroud and successfully ejected and saved at h ~40 km, v ~3.5 M.

Buran had two ejection seats derived from the aviation one. They should get away for 500 m after 9..10 s flight, on T+0..102.

https://translate.google.com.tr/translate?sl=ru&tl=en&js=y&prev=_t&hl=ru&ie=UTF-8&u=http://www.buran.ru/htm/katapu.htm

15 hours ago, sevenperforce said:

The crossrange requirement was pathetic.

Afaik, the crossrange requirement was wished by militaries.
While a civil ship follows the same set of trajectories, the military one can be returning from an orbit with custom inclination.
Say,  after a short-term single-turn recon mission (the main idea of the early spaceplanes of 1960s).
So, it has to land on an airbase, and requires enough great distance of the crosswind maneuver.

***

If Challenger had ejection seats, I guess they could eject after the cabin separation.
The cabin obviously survived a hydrogen tank explosion rapid fire and two SRBs fly-by.
Imho, the Shuttle could be safer if they:
1) Made the cabin attached with a decoupler to let it separate without metal crashing.
2) Added small separation engines to the cabin. Not a full-featured LES, but just to push it away for 10-20 meters from the rocket, to stay it more intact. Though, it's not necessary.
3) Used ejection seats for everybody on the upper desk, starting up. For the lower deck - starting down (like in some bombers).

Link to comment
Share on other sites

23 minutes ago, kerbiloid said:

Used ejection seats for everybody on the upper desk, starting up. For the lower deck - starting down (like in some bombers).

Trouble there is, the shuttle cabin actually had three decks.  There was an additional equipment deck I think a couple of meters deep below the mid-deck. It’s getting those middeck crew out that’s the real rub.  

Cleanly and properly separating the crew cabin, with its myriad of signal cables, power cables, hydraulic lines, etc, was deemed to be so difficult it simply wasn’t worth perusing. 

There actually was some consideration given to putting a huge Apollo-style capsule in the cargo bay, with its own escape system to blast it right through the CBDs, and here is where the crew would huddle for launch and landing.  

But, y’know, mass penalties and all... <_<

Link to comment
Share on other sites

5 minutes ago, CatastrophicFailure said:

Cleanly and properly separating the crew cabin, with its myriad of signal cables, power cables, hydraulic lines, etc, was deemed to be so difficult it simply wasn’t worth perusing. 

It has separated even without a decoupler. It wouldn't get worse.

6 minutes ago, CatastrophicFailure said:

There actually was some consideration given to putting a huge Apollo-style capsule in the cargo bay

Which wouldn't save any of those two shuttle crews.

***

Yes, the third deck is a problem.

Link to comment
Share on other sites

9 minutes ago, CatastrophicFailure said:

There actually was some consideration given to putting a huge Apollo-style capsule in the cargo bay, with its own escape system to blast it right through the CBDs, and here is where the crew would huddle for launch and landing.  

 But, y’know, mass penalties and all... <_<

I’m still juggling that idea of an assyemtric oversized Soyuz with a windscreen packed into where the two/three decks normally went.

Link to comment
Share on other sites

8 minutes ago, kerbiloid said:

Which wouldn't save any of those two shuttle crews.

 

It was conceived of specifically to save crews in exactly those circumstances...  ;) A self-contained capsule with its own abort system, heat shield, etc...

 

7 minutes ago, DDE said:

I’m still juggling that idea of an assyemtric oversized Soyuz with a windscreen packed into where the two/three decks normally went.

More or less that, but in the cargo bay. 

Link to comment
Share on other sites

52 minutes ago, CatastrophicFailure said:

More or less that, but in the cargo bay. 

Yeah, I can see why that would be unpopular.

Although Zarya was apparently designed with Buran’s payload bay in mind...

Link to comment
Share on other sites

3 hours ago, kerbiloid said:
3 hours ago, CatastrophicFailure said:

Cleanly and properly separating the crew cabin, with its myriad of signal cables, power cables, hydraulic lines, etc, was deemed to be so difficult it simply wasn’t worth perusing. 

It has separated even without a decoupler. It wouldn't get worse.

 

The orbiter breakup in the Challenger disaster did separate the crew cabin more or less cleanly from the rest of the vehicle structure, as far as can be determined. But there was no guarantee that this would happen.

If Challenger had been equipped with ejection seats that fired as soon as the orbiter started to break up, they all would have been dead. The only way it would have worked would have been if the cabin fell clear of the explosion and then the eject was manually triggered.

Link to comment
Share on other sites

On 2/26/2019 at 11:40 AM, CatastrophicFailure said:

Still not survivable. The shuttle, especially in the early days, had huge “black zones,” where any kind of failure requiring an abort would be LOCV, either due to reentry stress on the orbiter or lack of thrust/control. Remember, at launch the boosters gave 90% of the stack’s thrust, until the orbiter/ET combo could accelerate itself, even “shutting off” the boosters would be LOCV.

The pilot/commander on those first few flights of Columbia pretty much knew if anything went wrong while the boosters were burning they were boned. Oddly enough, that part never changed with “operational” flights. :huh:

My understanding was that the known size of the "black zones" only increased, as simulation after simulation of those aborts continued to fail.

Link to comment
Share on other sites

Not knowing to c&p between threads or quote something someone else quotes...

Sevenperforce asks why they didn't put thrust termination on the Shuttle SRB's - and there's a simple answer:  It wouldn't work.

Terminating SRB thrust meant the SRB's would go from "pulling" on the stack to "hanging off" the stack, the resulting transient shock loads would shred the ET and toss the orbiter uncontrolled into the air stream.  There, as happened to Challenger, aerodynamic forces would turn the Orbiter into confetti.  The only way around this was to put a SRB on the Orbiter itself, and use it to power the Orbiter away from the disintegrating stack.  Problem was, even using this SRB for orbital insertion, it was too heavy and basically wiped out a large fraction of the cargo capacity.

As to the never used "1 orbit capacity"...  No, they never used the entire amount of crossrange available - but they routinely used the crossrange capability to widen abort and landing windows.  (Or to create them were the window wouldn't have existed without the crossrange capacity.)  Here's a handy little PDF from NASA that shows the amount of crossrange used at landing through STS-88.

Link to comment
Share on other sites

4 hours ago, DerekL1963 said:

Sevenperforce asks why they didn't put thrust termination on the Shuttle SRB's - and there's a simple answer:  It wouldn't work.

Terminating SRB thrust meant the SRB's would go from "pulling" on the stack to "hanging off" the stack, the resulting transient shock loads would shred the ET and toss the orbiter uncontrolled into the air stream.  There, as happened to Challenger, aerodynamic forces would turn the Orbiter into confetti.  The only way around this was to put a SRB on the Orbiter itself, and use it to power the Orbiter away from the disintegrating stack.  Problem was, even using this SRB for orbital insertion, it was too heavy and basically wiped out a large fraction of the cargo capacity.

Challenger's breakup was inevitable, but the sequence itself is worth examination. As the starboard booster's O-ring burn-through began to sap its thrust, the TVC system on the port booster gimballed out hard in an attempt to compensate. The starboard booster's thrust kept dropping, however, and eventually the stack began to yaw to starboard. Aerodynamic stresses on the wounded booster skyrocketed and the aft attachment to the external tank, already weakened by impingement from the venting burn-through, gave way. The external tank failed, but the still-thrusting port booster did the most damage, causing accelerating yaw which resulted in vehicle breakup. The starboard booster, flopping wildly, tore off the orbiter's near wing, but at that point it was far too late anyway.

Thrust termination would not have saved Challenger because the stack didn't have a full gee of thrust without the boosters at T+73 and it would have tumbled. However, the SSMEs had less than a gee even at separation; at sep (T+120) they gave about 7 m/s2. So if the STS had been equipped with thrust termination on the boosters and that O-ring had lasted only a dozen seconds more, there would have been at least twenty seconds--fully a 6th of the booster burn time--during which a thrust shortfall could have triggered simultaneous booster shutdown and clean separation, with the SSMEs having just enough sustainer authority to keep the stack flying straight. It still would have been an abort, but it would have given them a chance.

Link to comment
Share on other sites

8 hours ago, DerekL1963 said:

Terminating SRB thrust meant the SRB's would go from "pulling" on the stack to "hanging off" the stack, the resulting transient shock loads would shred the ET and toss the orbiter uncontrolled into the air stream.

Wouldn’t it the loads be rather lightened because SRB thrust termination involves ejecting all of the unburnt fuel?

8 hours ago, DerekL1963 said:

The only way around this was to put a SRB on the Orbiter itself, and use it to power the Orbiter away from the disintegrating stack.  Problem was, even using this SRB for orbital insertion, it was too heavy and basically wiped out a large fraction of the cargo capacity.

I’m sorry to bring this thing up all the time... but we’ve only got two shuttles to go around.

The Buran was to fire a combination of its two 90 kN main engines and four 28 kN solids of some kind, each of which had the same power as each of the Shuttle’s OMS engine. This apparently was an adequate replacement for the twin mini-SRBs found under the OMS pods on the design studies of the “STS replica” period.

Spoiler

Bonus content: bad case of wishful thinking 

16a_razdelen.jpg

 

On 2/27/2019 at 11:18 AM, Xd the great said:

Elon musk: I hate SRB.

Everyone else: *stares*

Singular?

No wonder he hates the Synth Retention Bureau, he’s a bit of a BoS guy with all of his concerns about AI.

Link to comment
Share on other sites

1 hour ago, DDE said:

Wouldn’t it the loads be rather lightened because SRB thrust termination involves ejecting all of the unburnt fuel?

Uhm... No. All you're doing is dropping chamber pressure to near-zero, which slashes the burn rate of the fuel and the thrust produced. Any unburned fuel is still in the casing, burning (relatively) slowly and generating copious amounts of smoke and fire, but the gases that are produced are being vented out of both the nozzle and the holes punched in the casing by the thrust termination system. From what I understand, the plan usually called for punching the holes near the top of the casing.

Link to comment
Share on other sites

33 minutes ago, MaverickSawyer said:

Any unburned fuel is still in the casing, burning (relatively) slowly and generating copious amounts of smoke and fire

Not what I’ve heard about Minuteman thrust termination. Apparently a blown-out nozzle would suck most of the contents out and snuff the rest.

Link to comment
Share on other sites

9 minutes ago, kerbiloid said:

But how can they operate like a Minuteman

The Miniteman requires precise thrust termination; solid motors aren’t known for that. This is apparently achieved by blowing the nozzle end wide open, and the resulting shift in pressure sucks out most of the remaining propellant.

The Shuttle, AFAIK, accepts that the SRBs are still slightly burning when they’re separated.

Edited by DDE
Link to comment
Share on other sites

2 minutes ago, DDE said:

The Miniteman requires precise thrust termination; solid motors aren’t known for that. This is apparently achieved by blowing the nozzle end wide open, and the resulting shift in pressure sucks out most of the remaining propellant.

I mean the radial retronozzles in the upper part of the stage.
They would hit the tank and the shuttle.

Edited by kerbiloid
Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...