Solid vs Liquid Rocket boosters on Shuttle

[le3119]

I understand that solid fuel rockets burn out once ignited, you cannot turn them on - off and then on again. Could we develop a solid fuel rocket that could be turned off and on, would we want to (in terms of economics)? <br /><br />

 

[drwayne]

Actually, there are (on a much smaller scale) multiple pulse solid rocket motors in which separate firings, or pulses can be triggered as/when needed. <br /><br />There are also hybrid solid rocket motors, in which the oxidizer is not pre-mixed, but is pumped in. By controlling the oxidizer, these can be turned on and off.<br /><br />Note that solids can be "programmed" with a thrust profile, by controlling the grain and shape of the solid mixture. This is done on the shuttle already to control stresses in the vehicle.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[mrmorris]

<font color="yellow">"Could we develop a solid fuel rocket that could be turned off and on..."</font><br /><br />Essentially, 'we' have. That's what a hybrid is. It has a solid propellant and a liquid (generally) oxidizer. To 'turn it off', you stop the flow of oxidizer. <br /><br />The problem with 'turning off' a conventional solid is that the solid contains both propellant and oxidizer. This makes it much simpler in operation than a liquid booster, and somewhat simpler than a hybrid, but there's simply no 'off' switch. Once it's lit, there's no stopping it.

 

[tap_sa]

<font color="yellow">"Once it's lit, there's no stopping it."</font><br /><br />Actually there is, but it's usually of one-shot nature. Missiles and other solid LVs do thrust termination by opening extra exhaust ports to the forward end of the motor case, usually using explosives. The reserse flow negates thrust, and the rapid depressurization usually extinguishes the combustion process. Pressure drops - /> temperature drops -> less solid propellant is being gasified -> burning slows down -> pressure and temp drop even faster -> combustion terminates.<br /><br />A huge robust unobtainium-valve in the forward end of the case would make nice restartable solid motor <img src="/images/icons/smile.gif" />

 

[drwayne]

The cool thing (for me) about thrust terminating solids is the very bright glop that can fly out of the port.<br /><br /><img src="/images/icons/smile.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[tap_sa]

It's the ejected reactor core <img src="/images/icons/wink.gif" />

 

[drwayne]

I thought it was the warp core...<br /><br />Big <img src="/images/icons/wink.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[dwightlooi]

<i>Energia used liquid, but were they hypergolic or LO2/Kerosene?<br /><br />It lives on as the Zenit booster stage - it's a LOX/Kerosene motor. </i><br /><br />Actually, it goes further than that. The Energia used the RD-170 engine which continues its service as the RD-171 in the Zenit. The RD-171 differs from the RD-170 primarily in the fact that it is two axis gimballed instead of one axis in RD-170. The Zenit booster is the launch vehicle used by Energia-Boeing's Sea Launch float, mobile, equatorial platform launch service.<br /><br />But the engine actually goes beyond staying around and giving good service. The US's new Atlas V launch vehicle actually uses half of the RD-170/171! The Atlas V's RD-180 main engine is essentially a two chamber version of the four chamber RD-170.<br /><br />So the energia's engines not only lives on, it has kids!

 

[drwayne]

God kids too.<br /><br /><img src="/images/icons/smile.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[syndroma]

> <i>So the energia's engines not only lives on, it has kids!</i><br /><br />And even grandchildren. RD-191 is a half of the RD-180 and a quarter of the RD-171. It's going to be used in new age Angara LVs.

 

[spd405]

Going off topic here but what material are the shoulder patches the shuttle crews wear made of?

 

[spd405]

Just ordinary fiber like any shoulder patches. Why do you ask? <br /><br />Ongoing conspiracy theory elsewhere about 9/11 and some ID's being found in the wreckage - it was pointed out that crew patches had survived Columbia's break up (not sure if this is true)<br /><br /><br /><br />

 

[najab]

The patches being talked about weren't the ones on the launch/entry suits, but a box of them which were being flown to be distributed as mementos. <br /><br />They survived because the box probably kept them safe through peak heating, and then their high drag coefficient meant that they slowed right down very quickly and fluttered down to the ground.

 

[drwayne]

Somehow I don't think that data will work its way into the conspiracy...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

Nature is funny, did y'all see the Titanic expedition that James Cameron did a week or two ago, where the clock was still sitting on what was left of the mantle in the Strauss' room?<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[propforce]

<blockquote><font class="small">In reply to:</font><hr /><p>To the best of my knowledge, the Brazilian rocket ignited because the ignition circuits were inadvertently energised. <br /><p><hr /></p></p></blockquote><br /><br />You're probably right. I was recalling from memory which, as you know, is the 2nd thing to go with age. <div class="Discussion_UserSignature"> </div>

 

[frodo1008]

There is another reason why liquid engines are safer than the excellent post of propforce stated. That is simply that you can’t use the very same solid for your actual launch vehicle that you used to test the safety of your solid systems with! <br /><br />This means that you MUST depend completely on your manufacturing processes to make sure that every single motor is EXACTLY the same as those that you tested. Now I know that the solid motor industry have actually done a very good job of doing this, but it IS still a factor in engines safety.<br /><br />On the other hand every single liquid engine that is built is given a "Green Run", this means that the engine is prior run enough to find out if there are any problems with that particular engine. Then this VERY SAME engine is shipped and used on the actual launch vehicle itself!<br /><br />This can’t possibly be done with solids as when you test a solid, it is history, it IS gone! Used up, no more!<br /><br />THIS is why no less a rocket scientist than Wherner Von Braun insisted that there would be no solids used to propel, or even help propel human beings into space!<br />Well, he did relent in that the Apollo capsule escape system motor was solid. But of course, it was very sincerely hoped that system would never have to be used!<br /><br />Now, even with this inherent advantage even liquid engines have been known to fail. We are talking temperatures and pressure here that are far higher than even jet engines! But, this applies equally to both liquid and solid systems, and if you don't think that such temperatures and pressures can also make solids fail, then think of the Challenger accident!!<br /><br />So this gives liquid engines an inherent safety advantage over solids that solids will NEVER be able to match! <br /><br />While I guess that Mike Griffen is going to use SRB's to launch NASA people into space I would have to admit that this is one place that I think that saving money is foolish! <br /><br />If the curren