STS-114 Mission Update Thread (Part 3)

[robot_pilot]

>I think the exhaust plumes appear to 'flare' out as the air density<br /> />gets lower,<br /><br />(that is correct, and part of the reason an aerospike engine performs better at altitude than at sea level... but that's off-topic, sorry)<br /><br /> />but I was really starting to get a bit nervous on the SRB's just prior<br /> />to Sep and burnout. They looked to be burning a lot 'redder' than I<br /> />remembered previously, and I had a queazy feeling in my stomach<br /> />that flame was going to engulf the SRB's any second. <br /><br />Oh yes, especially since 51-L many of us have that same queasy feeling. The sight of the SRB plumes licking the bottom of the ET ("plume recirculation") has given many a manager a near-coronary since 1986, too...<br /><br /> />I dismissed this for the reasons stated above, and because this is<br /> />the first time I have watched a launch on a TV set rather than in<br /> />a small Windows Media Player box. However, it was very un-nerving<br /> />to watch. <br /><br />I couldn't agree with you more. Since 51-L (Challenger's last mission) I only watch my displays, don't even look over to the monitors because it makes me too nervous. Even the Apollo missions had a lot of plume expansion that looked dangerous - as if the vehicle would be swallowed up by them - but it's a perfectly normal part of spaceflight. I don't think I'll ever, ever get used to it either... and I know several other people who feel the same way.<br /><br />The advantage of the SSME plumes, in this regard, is that they are more or less invisible so they don't scare the daylights out of everyone when they're expanding, recirculating, and so forth.<br /><br />

 

[robot_pilot]

>I actually think the first time we did the OMS assist was done was<br /> />on the Nerolab mission. STS-90. One of my ex-engineers was on<br /> />that flight, her first flight after becoming an astronaut.<br /><br />What a unique perspective... we don't get to _meet_ very many astronauts, and here you've worked with one (at least one).<br /><br /> />Or it was one of the first to use OMS assist. <br /><br />That's what I was thinking of, "OMS assist". Sorry, OMS-1 is indeed different - but perhaps the original question was about OMS assist. That's how I took it anyway.<br /><br />Thanks for that info.

 

[Leovinus]

I want to know what this was. On the ET video for 2 or 3 frames, a firey explosion appears on the right side of the orbiter like something hit it and vaporized. Nobody has talked about it that I know of. <div class="Discussion_UserSignature"> </div>

 

[lunatio_gordin]

I don't remember seeing that... It definitely looks like foam.

 

[nacnud]

From the NASA video of the launch now showing on NASA TV the OMS engines fire from just after SRB separation for about another 2:19. IIRC you get less gravity losses the quicker you accelerate. Is the OMS firing to keep the acceleration as close to the 3g max acceleration while the vehicle is still too heavy for the SSME to do it alone?

 

[SpaceKiwi]

Obviously the OMS burn on ascent does provide a little extra punch, but it does seem illogical to me on the face of it. How do these engines with much lesser thrust contribute to the overall performance?<br /><br />My analogy would be a child and an adult on a tandem bicycle. The adult pedals with far greater rpms and, while the child also pedals, he/she doesn't pedal with sufficient velocity to contribute anything to the forward momentum. Isn't it a similar case with the OMS? <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[drwayne]

"Even the Apollo missions had a lot of plume expansion"<br /><br />The Saturn 5 first state was quite pronounced in plume envelopment as its (hydrocarbon) exhaust led to a more sooty plume.<br /><br />As I mumbled earlier, this is the result of the shock layer detaching from the aft of the vehicle and moving up the vehicle as speed increases an atmospheric density decreases.<br /><br />With the solids, you also see the effects of chamber pressure rolling off...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[Leovinus]

It was quick -- you'd have to go frame-by-frame on a digital recorder to see it best. It looks like fire, not foam. <div class="Discussion_UserSignature"> </div>

 

[nacnud]

<font color="yellow">I think the idea is just to add Delta V. <br /><br /><font color="white">Yeah, I was trying to work out the most effiecnt time to do the burn.</font></font>

 

[nacnud]

<font color="yellow">It looks like fire, not foam.<br /><br /><font color="white">Could you smell burning feathers? <img src="/images/icons/smile.gif" /></font></font>

 

[Leovinus]

I said it looks like fire, not foam. It's bright and hot-looking and expanding like an explosion. <div class="Discussion_UserSignature"> </div>

 

[Leovinus]

If the SRB exhaust hit that bird, there won't be much left but ashes. <div class="Discussion_UserSignature"> </div>

 

[ehs40]

i have a question for shuttle guy. how quickly can the shuttle be ready to go back to space after it lands?

 

[chebby]

Hey shuttle_guy,<br /><br />congratulations on this great launch! To my shame this is the first shuttle launch I ever saw. At least today I gave a good reason at work for being late <img src="/images/icons/wink.gif" /> <br /><br />The cameras between the tank and the orbiter, that's a new addition, right?<br /><br />I hope the mission and the landing will go just as flawlessly. Good luck! (they don't say break a leg/wing in NASA, do they?)

 

[spacefire]

probably faster than it'd take you to raise 200mil <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[ehs40]

lol 200 mill u would have to b a rockstar to make that much quickly

 

[ehs40]

thanks shuttle guy i thought it might take like a week or something and congrats to you and nasa on a great launch

 

[spacefire]

that's approximately how much a Shuttle launch costs<br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[nacnud]

That depends on who you ask...

 

[ehs40]

i thought each launch cost 500 million......um shuttle guy a little help?

 

[najab]

><i>I thought each launch cost 500 million....</i><p>That all depends on what you define as the 'cost' of a shuttle mission. <li>If you take the cost of the Suttle program to date (development and operation) and divide it by the total number of flights to date, you'll get ~$800M per flight. <li>If you take the <b>entire</b> Shuttle portion of the HSF budget and divide it into the number of flights, you'll get $500-600M per flight.<li>If you take the "Launch Operations", "Processing" and "Hardware" line items of the Shuttle budget (I probably have the item names wrong, since I'm going by memory) and total them and divide the result by the number of flights, you'll get ~$200M per flight.<li>Finally, if you look at the cost of <i>adding</i> a flight to the manifest, it gives you ~$100M per flight.</li></li></li></li></p>

 

[ehs40]

thanks for the info najab but dose any one know how much horse power the shuttle has

 

[halman]

SpaceKiwi,<br /><br />You must bear in mind that the performance of an engine is directly proportional to the weight it is accelerating. Firing the Orbital Maneuvering System engines at take-off would have practically no effect, because the weight of the stack is several million pounds. However, by the time the Solid Rocket Boosters have seperated, the vehicle weight is down cosiderably, (I don't know the exact weight,) so even small engines like the OMS can have significant impact on the vehicle velocity. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[halman]

robot_pilot,<br /><br />It is nice to know that there is another NASA 'insider' posting here. If you can tell us your job without compromising it, we all would be interested. <br /><br />How soon after launch does Houston take over the flight? <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[halman]

shuttle_guy,<br /><br />The earlier posts regarding release sequencing of the hold down bolts and your report that the crew stated this was the smoothest ride the verterans could remember brought the first flight of Columbia to mind. When the Solid Rocket Boosters ignited, the whole stack kicked sideways about 4 meters. Apart from the pad abort I saw once, that was the scariest thing I ever saw a rocket do! <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>