Re: Are Solid Boosters Safe?

"Dale" <drc@xxxxxx> wrote in message
news:mjl961psi1gta6u3esi6q9n124gv947ts6@xxxxxxxxxx
>
> Pretty sure SRB thrust is greater than the tensile strength of the bolts.
> At most, it would probably just pull up a chunk of the pad as it
> pinwheels.
> If memory serves, explosive hold-down bolts have failed before, without
> much effect on the launch.

Each SRB has four 3.5 in. dia. hold down bolts. Steel tensile yield strength
is roughly 500 MPa (72518 psi). Thus each bolt can hold 697,000 lbs,
or 5.57 million lbs for all eight.

Each SRB produces about 3.3 million lbs thrust, so it does appear the total
thrust exceeds the tensile strength of the SRB hold down bolts.

http://www.answers.com/topic/space-shuttle-solid-rocket-booster

However I don't think a hold down bolt has ever failed to detonate. They're
crit 1 items so any failure would be loss of vehicle.

There was one failure of the redundant firing circuit for the hold down
bolts on STS-112.

http://www.spaceflightnow.com/station/stage11a/021028holddown/
http://www.aviationnow.com/avnow/news/channel_awst_story.jsp?id=news/0512shuttle.xml

The obvious question is why not make the bolts slightly bigger to
hold down the vehicle even if an SRB is slow or fails to ignite.
After all the Saturn V was held down against 7.5 million lbs thrust.

My guess is the pad and vehicle aren't designed to withstand
an SRB running for several minutes while held down.

Also a failed SRB ignition is very unlikely, as the igniter circuitry
is multiply redundant.


.

Relevant Pages

  • Re: Are Solid Boosters Safe?
    ... >> Pretty sure SRB thrust is greater than the tensile strength of the bolts. ...
    (sci.space.shuttle)
  • Re: STS51L Accident Questions
    ... >on the pad while the crawler transports it etc. ... rip free if this were to happen, and that it doesn't use explosive bolts ... If one of these fails, no problem, the SRB just rips it out of its ... they are secured by explosive nuts. ...
    (sci.space.history)
  • Re: shuttle, tank and boosters on its crawler
    ... Are they also designed to break when the SRB thrust ... The bolts themselves don't destruct, ... As you can see there are two charges, one on either side of each nut. ... I'd be more worried if one SRB failed to ignite. ...
    (sci.space.shuttle)
  • Re: shuttle, tank and boosters on its crawler
    ... on the two SRB nozzles that the MLP is supporting? ... which is lifted by the crawler and moved to the Pad.. ... Each SRB is attached to the ET by 4 bolts (3 ... launch site with the shuttle attached to the pad. ...
    (sci.space.shuttle)
  • Re: CEV cost SKYROCKETING!
    ... SRB for CaLV. ... Keep in mind that this extra cost is a small percentage ... This might cost even more because a new upper stage, ... The Delta IV upper stage has an initial thrust to weight ...
    (sci.space.shuttle)