Falcon 1 Launch: December 19 at 11 a.m. PST (7 p.m. GMT)

[nacnud]

But an evacuated tank falling back into the atmosphere may have problems, especially as the first stage of the Falcon I is expected to be reusable.

 

[henryhallam]

True enough.. I will be interested to see whether that reusability goes as planned anyway.

 

[mlorrey]

Sure, but its still a pressure differential issue. If internal pressure is still ten times 200kft altitude pressure, it likely won't matter. 200kft is nearly nothing, doesn't take much to be ten times that.<br /><br />Propforce is hyperventilating. The problem was not with the tank, it was with the valve. The pump was not on the vehicle, so it therefore follows that without such a pump on the vehicle, that the worst that can happen is that the tank will evacuate to ambient pressure. Separation is at MEC, therefore there should be minimal compressive forces upon the tanks, as the vehicle would be in free fall.

 

[henryhallam]

Thanks for the clarification shuttle_guy. Mlorrey, I think the worrying situation is that while <i>on the pad</i>, if the tank had not only buckled as it did but collapsed, then the vehicle including the (still full?) second stage would have been destroyed, perhaps with a big explosion!

 

[CalliArcale]

Yep. They came awfully close to disaster. It's still not good news; they will have to fix it, and I rather doubt they can just bang the tank out with a hammer out there on Omelek Island. They're going to have to bring out a new first stage, I expect. That could delay them a lot. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[spacefire]

could this buckling have anything to do with the manufacturing methods used by SpaceX in order to make the rocket cheaper/lighter?<br />Maybe a sturdier tank wouldn't have buckled? <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tap_sa]

<font color="yellow">"Maybe a sturdier tank wouldn't have buckled?"</font><br /><br />Tank internal pressure went below ambient, something that should <i>never</i> happen. No need to redesign the tank but keelhaul the persons responsible for the pressurization valve.<br /><br />If Falcon would have gotten off the pad and this malfunction occured during the flight it would have most certainly meant loss of vehicle due to loss of structural integrity and/or fuelpump cavitation (NPSH falling too low).

 

[josh_simonson]

Most other rocket's fuel tanks would probably buckle if you pulled a vacuum in them too. Many 'pressure stabilized' tanks such as those of the Atlas II are even flimsier than those of the falcon. In a launch, you would never have a vacuum (or even close) in the tanks because they are pressurized with helium. <br /><br />Probably the de-fueling parts (such as this valve) are lower reliability parts since they aren't needed for a successful launch. Perhaps the valve is operating near it's minimum temperature rating or something (being in the vicinity of LOX). Anyway, with this fiasco I'm sure they'll revisit the reliability of these things and improve their test procedures to weed out bad parts.<br /><br />

 

[spacefire]

<br />yeah, that makes sense I guess.<br />What a silly reason for failure though! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[mikejz]

How fast do you think the 'issue' too to happen. Would a more active monitoring of tank pressure/software check prevented such a mistake?

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>What a silly reason for failure though!<p><hr /></p></p></blockquote><br /><br />Well, it's usually the little things that'll get ya in this business. Maybe people tend to be more careful with big things, or maybe it's just the sheer number of little things that allows problems to be overlooked more easily.<br /><br />It should be relatively easy to make sure this doesn't happen again, so that's the silver lining here. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[yurkin]

There was an article on SpaceXs website a while ago talking about how the valves on Falcon cost as much as a luxury. But it was well worth it since many rockets have failed due to faulty valves. Kind of ironic.

 

[henryhallam]

Question: Is it practical to make every valve on a vehicle a redundant series-parallel set? If not, how do you decide which are the "important" ones?

 

[josh_simonson]

It could be they detected the electrical fault and scrubbed the launch, then the faulty part went and damaged the rocket...

 

[mikejz]

Just wondering: Had the wind NOT been an issue and the Falcon launched, what, if any, failure modes exist for the valve failing?

 

[jamie_young]

Glad they didn't have a loss of vehicle, that would make this problem seem small.

 

[thinice]

They were lucky the whole structure didn't fall to the side and they didn't loss the payload.

 

[jamie_young]

If it was an explosion on the pad, would it have risked the people on the island or are they far enough away to be safe?

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>"Is it practical to make every valve on a vehicle a redundant series-parallel set?"<br /><br />Certainly, other wise you are flying with single point failures.<p><hr /></p></p></blockquote><br /><br />To elaborate, it is not practical to make everything multiply redundant, so indeed you do have to make decisions, prioritizing what is most important to back up, and then judging whether or not it's actually practical to do so. For instance, we've been told that a gear-up landing of a Space Shuttle Orbiter is not considered survivable. But it's not practical to have redundant landing gear. When it's not practical to back up a particular item, you instead put your effort into making it as rugged as you possibly can. Systems for deploying the gear have backups, for instance, so they've reduced as much as they can the risk of the gear failing.<br /><br />But if something is a single point of failure, and it's practical to give it some kind of backup (not neccesarily an identical redundant part or system), then you really must do so. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[cretan126]

Shuttle_guy, I think you are misinterpreting the order of events. It sounded to me like they were 'holding', waiting for the winds to drop to a low enough level. As they did during the LOX-fiasco in November, they were draining some fuel to reduce the LOX boil off and keep from overchilling the fuel. This process caused the 'suction-pucker' which led to the abort.<br /><br />BTW: 24 knots seems like a ridiculously low wind limit. If you look at the historical Kwaj met data, the mean wind this time of year is over 17 kts. That doesn't leave much room to maneuver if you want to launch in a 'responsive' manner. Luckily for them, FalconSat is a simple experiment and isn't (and can't be) fussy about the launch window. This is not typically the case for more complex spacecraft (i.e. true paying customers).

 

[nacnud]

24 knots is a force 6! That is a lot of wind.

 

[josh_simonson]

I wouldn't go boating in 23kt winds, not surprised they wouldn't go rocketeering in that either.

 

[nacnud]

I used to live for the windy days, luckily dinghy masts bend straight again if you are careful <img src="/images/icons/smile.gif" /><br /><br />

 

[cretan126]

Shuttle_guy,<br />Roger that. At the time the tank got sucked in, they were just biding time, waiting for lower winds. And, speaking of winds,...<br /><br />Josh/Nacnud, <br />I didn't mean to imply that 24 kts isn't a particularly windy day (although, personally, I have gone sailing AND been intimately involved with rocket launches in similar winds - both were rather exciting). Rather, for a rocket that is supposed to be demonstrating responsive capability, a 24 kt limitation can be resasonably expected to cause delays. <br /><br />The Delta II wind limitation for launch is 35 kts (based on their payload planners guide), although there are some regions of lower speeds in cold temperatures (probably due to thermal cooling on the booster, not wind loads). The mobile service tower limit to be moved is 36 kts. This is a much bigger rocket than Falcon I (i.e. higher wind loads). For a more comparable rocket (and equal time), Lockheed Martin's Athena has a launch limit of 45 kts. <br /><br />With so many other things that can cause launch delays when trying to launch a complex rocket, something as expected and addressable as winds shouldn't be a driver.