Re: Are Solid Boosters Safe?

On Tue, 19 Apr 2005 08:18:50 -0500, Joe D. wrote:

> "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.

Don't forget to subtract the weight of the vehicle from the thrust. The
Saturn V lifted off at 1g, so the bolts didn't hold much force. 1g of
thrust - 1g of gravity...

--
Craig Fink
Courtesy E-Mail Welcome @ WeBeGood@xxxxxxxxx
.

Relevant Pages

  • Re: Are Solid Boosters Safe?
    ... > Pretty sure SRB thrust is greater than the tensile strength of the bolts. ... Each SRB has four 3.5 in. ...
    (sci.space.shuttle)
  • 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: 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)
  • 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: CEV and Stick
    ... > SRB that was still firing. ... Furthermore, thrust termination of solid ... If you thrust away a capsule under an escape tower just prior to thrust ... > away from the launch vehicle. ...
    (sci.space.policy)