Author Topic: Looking for comments on space policy and spacex strategies  (Read 1546 times)

Offline sugmullun

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   I'd like to post a few questions that I don't have the means to determine myself.
    Why the inability of the "space" community to come together under one roof and support something that moves us outward, instead of the constant belittling of each other's notions of what's the best way to go about it. This wouldn't be so bad if it were under one roof called, "Let's Go", where how to start could be hashed out, voted on by an elected group of qualified decision makers, but it’s not. I think that there are enough of us space fanatics to fund our own program if we’d just decide to put the doing above our individual pet “hows”. I think that however we decide it’d get done. The technical issues seem small next to the personal disagreements.
    I’ve been following SpaceX’s news for a little over a year and am excited about it. Win or lose Elon Musk can be proud of the attempt.
     I’m given to understand that there was a serious strategy to parachute recover the first stage of the Falcon 9 and upon an apparent determination this wasn’t practical or possible there was
a switch to full powered return of it and the second stage. Why the drastic level of change in method?  If the first was impossible then by extrapolation that would have said that the SpaceX organization isn’t qualified to launch rockets. So it was possible. Why not some “powered” modification to the parachute recovery? Just enough for the booster to survive and deploy chutes?  This is where I fall down. I don’t have the knowledge to word this out.
   Also of SpaceX: if they want to recover Dragon AND the second stage under power wouldn’t it be more practical to just leave them together? Based on the video (which I loved) they’ll need two heat shields, more fuel, engines, a “ separation thing which needs to work”, etc. Seems that the second stage flies to almost where dragon will go (for quite a while anyway)
   I’m looking forward to comments.

Offline Jorge

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   I'd like to post a few questions that I don't have the means to determine myself.
    Why the inability of the "space" community to come together under one roof and support something that moves us outward, instead of the constant belittling of each other's notions of what's the best way to go about it.

Because the current budget environment is constrained. It's pretty much a zero-sum game now; for one person's notion to get funded, most of the others will not get funded.

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If the first was impossible then by extrapolation that would have said that the SpaceX organization isn’t qualified to launch rockets. So it was possible.

Your conclusion does not logically follow from your premises.

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   Also of SpaceX: if they want to recover Dragon AND the second stage under power wouldn’t it be more practical to just leave them together? Based on the video (which I loved) they’ll need two heat shields, more fuel, engines, a “ separation thing which needs to work”, etc. Seems that the second stage flies to almost where dragon will go (for quite a while anyway)

No, not even close. Second stage goes to a low LEO while the rest of Dragon goes to ISS. Dragon cannot maneuver in proximity to ISS with the dead mass of the second stage hanging off it.
JRF

Offline sugmullun

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   I'd like to post a few questions that I don't have the means to determine myself.
    Why the inability of the "space" community to come together under one roof and support something that moves us outward, instead of the constant belittling of each other's notions of what's the best way to go about it.

Because the current budget environment is constrained. It's pretty much a zero-sum game now; for one person's notion to get funded, most of the others will not get funded.

My point being that a unified group would be much more influential and maybe able to insist on more funding for a PROGRAM and not this apparent view that each supporter's pet program is more important than SOME program.

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If the first was impossible then by extrapolation that would have said that the SpaceX organization isn’t qualified to launch rockets. So it was possible.

Your conclusion does not logically follow from your premises.

Yes it does. This point being that if it were impossible then SpaceX
wouldn't have pursued the possibility (due to their obvious ability to successfully launch rockets)

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   Also of SpaceX: if they want to recover Dragon AND the second stage under power wouldn’t it be more practical to just leave them together? Based on the video (which I loved) they’ll need two heat shields, more fuel, engines, a “ separation thing which needs to work”, etc. Seems that the second stage flies to almost where dragon will go (for quite a while anyway)

No, not even close. Second stage goes to a low LEO while the rest of Dragon goes to ISS. Dragon cannot maneuver in proximity to ISS with the dead mass of the second stage hanging off it.

Again: For brevity I was simplifying concepts....why not ONE vehicle instead of two if the DeltaVs aren't drastically different and if they are and you know, then by how much in comparison to what they're investing now?

Offline Jim

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   Also of SpaceX: if they want to recover Dragon AND the second stage under power wouldn’t it be more practical to just leave them together?

No, because not every Falcon 9 is going to have a Dragon on it.

Offline Antares

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Delta V is the wrong metric.  It's propellant mass.  If your stack is heavier, you need more prop.

Do you know anything about entry aerodynamics?  The shape of Dragon + Stage 2 is unsurvivable.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline strangequark

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Do you know anything about entry aerodynamics?  The shape of Dragon + Stage 2 is unsurvivable.

I understand the many reasons this is not a good idea as a whole, but I’m curious about this comment. Are you talking about bringing it in nose-first? I mean, if you were really intent on using something with that OML, it seems like you could bring it in on its “side” like an ugly biconic.

Offline sugmullun

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Do you know anything about entry aerodynamics?  The shape of Dragon + Stage 2 is unsurvivable.

I understand the many reasons this is not a good idea as a whole, but I’m curious about this comment. Are you talking about bringing it in nose-first? I mean, if you were really intent on using something with that OML, it seems like you could bring it in on its “side” like an ugly biconic.

I've not in the past paid any attention to the technical aspects of space flight.  I'm asking these questions as a part of trying to get  my mind around the challenges that are faced.
I don't see why DeltaV isn't a part of the metric. I assume that the second stage at cutoff is pretty much above the atmosphere and has at least most of the velocity it needs to stay there. FRom then on it's just DeltaV...or so I'm led to believe. And I do understand how that works.
As part of the back-and-forth it occurred to me that it'd be hard to
make a "long" reentry vehicle or that to have it come in nose first that there would be high G's in two directions on the occupants during the whole course of the flight.
I had already thought of the fact that the Dragon is already a developed craft...was just asking for the sake of the knowledge.
Still...the first part. Anyone know why a parachute return of the first stage didn't work (with some information) or why a partial powered/parachute reentry (using less launch weight) wouldn't work?

Offline QuantumG

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Why the inability of the "space" community to come together under one roof and support something that moves us outward, instead of the constant belittling of each other's notions of what's the best way to go about it.

and

Still...the first part. Anyone know why a parachute return of the first stage didn't work (with some information) or why a partial powered/parachute reentry (using less launch weight) wouldn't work?

are the same question. A bunch of people have come together under one roof and decided to work together - that roof is called SpaceX. Inside there are camps that think method A is better than method B, and at any given time one camp will be winning over the other. In regards to reusability, there's the parachute camp and the powered camp. Each set aside their differences and worked to give parachutes a go.. it failed. So now it's time to try powered. Why not some hybrid? Because parachutes already had their shot and it didn't work, now it's time to give the powered advocates their turn. If they fail then maybe a hybrid approach can be tried, but remember there's a third camp: wings.

That's how engineering works. Rational people can disagree on the best approach and only reality gets to decide who wins.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline sugmullun

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Why the inability of the "space" community to come together under one roof and support something that moves us outward, instead of the constant belittling of each other's notions of what's the best way to go about it.

I'm sure that the people who work for SpaceX were chosen partly for their ability to work together and that they work together partly because their boss told them to.
I don't think that's much related to the first question, which maybe I shouldn't have asked.
I don't doubt there are good reasons and maybe the only workable way for SpaceX to proceed is the way they are doing it.
My questions are for my understanding of the TECHNICAL part of the WHYs. I'm not getting much responce there. Thanks anyway.

Still...the first part. Anyone know why a parachute return of the first stage didn't work (with some information) or why a partial powered/parachute reentry (using less launch weight) wouldn't work?

are the same question. A bunch of people have come together under one roof and decided to work together - that roof is called SpaceX. Inside there are camps that think method A is better than method B, and at any given time one camp will be winning over the other. In regards to reusability, there's the parachute camp and the powered camp. Each set aside their differences and worked to give parachutes a go.. it failed. So now it's time to try powered. Why not some hybrid? Because parachutes already had their shot and it didn't work, now it's time to give the powered advocates their turn. If they fail then maybe a hybrid approach can be tried, but remember there's a third camp: wings.

That's how engineering works. Rational people can disagree on the best approach and only reality gets to decide who wins.

Offline Antares

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First stage recovery using parachutes is doubtful because pressures and temperatures and thermal loads vary with Mach squared.  Shuttle loses SRBs at Mach 8.  ELVs stage around Mach 11, so everything is twice as severe.

The existing shape of Dragon + Stage 2 will burn up hypersonically no matter the orientation with the velocity vector.

Your "why the inability" question is not a technical one.  It's a political one.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline ugordan

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Re: Looking for comments on space policy and spacex strategies
« Reply #10 on: 01/10/2012 08:02 PM »
Shuttle loses SRBs at Mach 8.

Mach 4.5?

Offline Antares

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Re: Looking for comments on space policy and spacex strategies
« Reply #11 on: 01/11/2012 02:05 PM »
Yeah, sorry, neurons crossed or something.  Maybe they were originally designed for Mach 8.  It's stuck in my head for some reason.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

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