Dragon v2 Kremlinology from Helodriver's unveiling pics

[Lars_J]

Call me a skeptic, but looking at how deep the SD nozzle + thrust chamber is (based on the exterior SD model), it is extremely unlikely that the floor would cause the inside of the thrust chamber to be that bright based on illumination reflected off the floor (as Helodriver says - apparently there was no linger on the camera). I don't buy it.

[cscott]

This is my thinking on this as well.   Not only could the legs take the loads the way the old attachments points did but the feet would be made from the same material as the old attachment points.

I agree with this.  I haven't studied all possible pictures of the underside yet, but I *think* there are only two "hard" attachment points on the bottom of v2, and the other four attachment points are the leg locations.  Since the attachment points are obviously made of some sort of metal (not PICA-X), it seems reasonable to assume that the footpads are the same (refractory?) metal.  The real question is how the footpads/leg extension mechanism is insulated to keep them from conducting heat into the frame.  But presumably they've already solved this problem on Dragon v1 for its attachment points.

[cscott]

Call me a skeptic, but looking at how deep the SD nozzle + thrust chamber is (based on the exterior SD model), it is extremely unlikely that the floor would cause the inside of the thrust chamber to be that bright based on illumination reflected off the floor (as Helodriver says - apparently there was no linger on the camera). I don't buy it.

It has been suggested (in the other thread) that what you are seeing is the pintle.

[MP99]

Hey Guys,
Is anyone able to help me out with the circular shape in this pic of HeloDriver
http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=34841.0;attach=586345;image

I've seen it on the old dragon heat shield too - just wondering what its purpose is

I believe that's a trunk attachment point.  There should be six of them.

Question re the dynamics of this, to someone who might be able to offer an engineering view on it:

Might a trunk attachment design be modified a bit for Dragon V2 where only three points (vs 6 in DV1) are the traditional SpaceX design (with the load member taking both tension and compression) while the remainder of the compressive loads during launch acceleration might be applied through a stiff load bearing point in the center of each of the four (retracted) landing legs?

In other words, with the four new breaks in the TPS for the four landing legs, might not they be able to transfer some substantial portion of the compressive acceleration loads to the capsule, while having a reduced number of the legacy attachment points that would handle both tension and compression, and it would be only three points that "hold the capsule and the trunk together."

Counter-argument:-

The legs are designed to support the weight of the capsule when they are extended, but probably softened by some sort of suspension. When they are retracted, I suspect the legs don't provide a particularly rigid support for the foot-pad.

However, the seal around the foot pads would be an ingress point for hot gasses during reentry. My thought is that this seal is critical, and you don't want to provide relative stresses between the foot and the gap that it beds into, since that might break the sealant material. (You will see that I am assuming they put sealant into that gap.)

Analogy - put a car onto a flatbed truck, and the body of the car will move up and down because the wheels attach via a suspension. Assuming Dragon's legs also have a suspension, this would be perhaps the least rigid point that the trunk could connect via. This also depends on the mechanics of how the legs are kept retracted until needed, by I don't think that mechanism needs the extra stress of reacting launch stresses up into the capsule.

cheers, Martin

[cscott]

The legs are designed to support the weight of the capsule when they are extended, but probably softened by some sort of suspension. When they are retracted, I suspect the legs don't provide a particularly rigid support for the foot-pad.

However, the seal around the foot pads would be an ingress point for hot gasses during reentry. My thought is that this seal is critical, and you don't want to provide relative stresses between the foot and the gap that it beds into, since that might break the sealant material. (You will see that I am assuming they put sealant into that gap.)

I also thought about that, but I'm guessing that the legs "bottom out" onto a hard connection to the frame.  So when the legs are at maximum compression it is the same as when they are locked for launch and the compressed piston is directly in contact with the frame.

I'm also assuming a metal-metal contact between the footpad and the "foot well", and that a seal isn't needed because the outside pressure will seal the gap itself by pushing the conical foot into the well.

Note also that small gaps aren't generally an issue for re-entry.  Heat transfer on this side of a blunt body is primarily by convection, and stagnant air doesn't convect heat.  The Shuttle gap-fillers were added to prevent *vortex formation* in the gaps, which would have transferred heat.  So in terms of sealing the foot-well, all that is required is that any gaps that exist are too small for vortex formation, and that the footwell as a whole holds pressure so that the gas can't force its way through to some other part of the structure.

That said, my main argument for the feet being load bearing during launch is simply the fact that I only saw one or two structural attachment points below dragon v2, and we know there ought to be more.  If someone can scour the published images and locate some more hard points that are not feet, I would reconsider.

References: https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system#Gap_fillers
https://en.wikipedia.org/wiki/Atmospheric_reentry#Blunt_body_entry_vehicles

[mme]

Call me a skeptic, but looking at how deep the SD nozzle + thrust chamber is (based on the exterior SD model), it is extremely unlikely that the floor would cause the inside of the thrust chamber to be that bright based on illumination reflected off the floor (as Helodriver says - apparently there was no linger on the camera). I don't buy it.

Presumably Helodriver got an up close look (from the SpaceX: Dragon V2 Unveil - Discussion/Party Thread):

I'm guessing the SuperDracos were not fitted into their ports, since it looks like there was light showing through from where the thrust chamber should be?

It doesn't look like light showing through but something shiny being illuminated by the camera light. The pintle would be a good guess. ...

The inside of the engine bells was silver metal, lit by the white light coming up from the illuminated platform floor below. ...

[clongton]

Call me a skeptic, but looking at how deep the SD nozzle + thrust chamber is (based on the exterior SD model), it is extremely unlikely that the floor would cause the inside of the thrust chamber to be that bright based on illumination reflected off the floor (as Helodriver says - apparently there was no linger on the camera). I don't buy it.

Lars, you're not seeing the forest for the trees:

Trees:   You don't understand how a lighted floor would reflect that brightly off the interior of the engine - that's understandable.
Forrest: An eye-witness account from a respected member of this forum who was hands on with the hardware and took those pictures that stated unequivocally that the engines were installed.

At some point you need to trust the word of such an eyewitness who was actually there when you actually were not. There are thousands of us who wished we could have been there but could not. We are grateful that a member as respected as Helodriver could be there to take those pictures, ask Elon questions, report the answers, tell us what he saw and answer our questions.

[Sean Lynch]

Hey Guys,
Is anyone able to help me out with the circular shape in this pic of HeloDriver
http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=34841.0;attach=586345;image

I've seen it on the old dragon heat shield too - just wondering what its purpose is

It's rather like a flat flange surface, a conical interface for a friction fit silicon seal...a plug in the end of a cylinder...guessing a trunk mount.

[Kabloona]

Looks like there be engines up those nostrils. So much for  the net trolls calling it a mockup.

Hmm, my assumption was that it would be dark up there if engines were fitted. I assumed the light coming down through those ports meant SDs were not fitted?

cheers, Martin

Not light, reflection on silver metal from the illuminated white floor.

Thank you Helodriver for your excellent video and reports from the unveiling. I apologize for questioning your report that the SD's were installed. Like several others I was misled by the appearance of light inside the nacelles and had not seen your explanation about reflected light. I regret if my posts on the subject seemed rude or ungrateful for your good work, which was certainly not my intent.

[meekGee]

Call me a skeptic, but looking at how deep the SD nozzle + thrust chamber is (based on the exterior SD model), it is extremely unlikely that the floor would cause the inside of the thrust chamber to be that bright based on illumination reflected off the floor (as Helodriver says - apparently there was no linger on the camera). I don't buy it.

Lars, you're not seeing the forest for the trees:

Trees:   You don't understand how a lighted floor would reflect that brightly off the interior of the engine - that's understandable.
Forrest: An eye-witness account from a respected member of this forum who was hands on with the hardware and took those pictures that stated unequivocally that the engines were installed.

At some point you need to trust the word of such an eyewitness who was actually there when you actually were not. There are thousands of us who wished we could have been there but could not. We are grateful that a member as respected as Helodriver could be there to take those pictures, ask Elon questions, report the answers, tell us what he saw and answer our questions.

I think Helodriver would sleep easier at night knowing that he's not considered infallible...

His opinion counts for more since he had a personal look, but people are entitled to form their own opinions too...

[rpapo]

<Mood = "Grumpy at all this second-guessing">
Sounds like next time there's an event like this, we have to have two guys there, looking at everything.  That way it's not so easy for people to think they know more about something they haven't seen with their own eyes.
</Mood>

[clongton]

... but people are entitled to form their own opinions too...

Yes they are but that's not exactly what's happening here.
Lars is directly and specifically contradicting what the eyewitness saw without any kind of justification what-so-ever. Whatever it takes to refute an eyewitness account is not being offered here; only a wag opinion, to which he is entitled, but not to accuse someone of an untruthful report.

Kinda disrespectful I think.

[cscott]

... but people are entitled to form their own opinions too...

Yes they are but that's not exactly what's happening here.
Lars is directly and specifically contradicting what the eyewitness saw without any kind of justification - what-so-ever. Whatever it takes to refute an eyewitness account is not being offered here; only a wag opinion.

Kinda disrespectful I think.

Just to take the devil's advocate side -- specifically what Helodriver said was that he saw "shiny metal" inside the draco bell.  It's *possible* that this was some sort of metal plug or cover.  I don't think we can say definitively that it was a flight-ready draco sitting in there.  But basically we have no evidence it was not (shiny metal is definitely consistent with it being a real superdraco), and we have EM's word that what was on display was "mostly" flight hardware.

But really I'm tired of both the original discussion and the meta-discussion about whether the discussion was worthwhile.  I wouldn't mind if the mods trimmed (this post and) everything but the posts directly quoting Helodriver.

[Helodriver]

I have no issue with anyone's interpretation here or do I feel any disrespect. I myself was skeptical there were real SDs up in those pods (why install them in a vehicle 2 years away from flight?) so when I was afforded direct access to the V2, it was one of the first things I looked at closely. Compared with the size of the Superdraco on display that I looked at briefly, the nozzle, nozzle throat, and overall depth of the space into the thrust chamber seemed to be the same size. The inside of the V2's SD thrust chambers were clearly a sliver reflective metal and the plastic floor was illuminated by white light from below, shining a lot of light upward. Could all eight have been detailed mockup engines? Its impossible to say without removing the exterior panels of the V2 and looking at the plumbing. The SD on display was wheeled away before I could look into its thrust chamber with a flashlight, (and I planned to do this) as the way it was displayed had it situated such that no light was shining up into it so I could not see if its internal configuration exactly matched what was mounded on the V2. Note I didn't post any closeups of the displayed SD myself, as it was removed fairly quickly after the presentation was over, while I was talking to Elon. Decisions, decisions...

[RanulfC]

I have no issue with anyone's interpretation here or do I feel any disrespect.

Prefectly all right sir, WE will be more than happy to take issue and claim disrespect in your stead... Don't put yourself out! It's quite allright, we have this one... Now please don't inturpt our arguments with statements of what you actually did or did not see or hear... We don't appreciate "facts" getting in our way...

 

Randy

[Profwoot]

Can anyone explain to me why it matters whether the unveiled capsule had SDs installed in it? I enjoy this forum, but constantly wading through arguments like this one really sours the experience. Let's just assume that we're all smart, well-informed people who don't need to get butthurt over every perceived slight.

[sojourner]

Can anyone explain to me why it matters whether the unveiled capsule had SDs installed in it?

It tells us a lot about how complete the capsule is.

[meekGee]

I'm one of those that thinks the actual engines may have been missing (Based on the video, and acknowledging HD's comments) - but my though was that they were removed for the show, and the capsule is actually rather advanced.

I also re-watched the bit where Elon rotates the overhead display.  Those screens are very very light.  You can see that by how fast they accelerate at beginning and end of motion.  I don't think there's 10 pounds hanging on that rotating truss.  The main mode frequency can be plenty high enough that it's not an issue.

[llanitedave]

Can anyone explain to me why it matters whether the unveiled capsule had SDs installed in it?

It tells us a lot about how complete the capsule is.

It really doesn't.  The Super Dracos seem to be modular, and should be relatively easy to install or remove.  Removing and replacing them may be part of regular maintenance.

[guckyfan]

It tells us a lot about how complete the capsule is.

It really doesn't.  The Super Dracos seem to be modular, and should be relatively easy to install or remove.  Removing and replacing them may be part of regular maintenance.

But it does. No SuperDracos would not tell us they are not ready. But having them installed tells us they are ready.