Author Topic: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)  (Read 183095 times)

Offline Jim

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #40 on: 10/03/2013 02:22 pm »
improvement that is common in consumer design and production, uncommon in aerospace.

That is untrue.   Look at every launch vehicle.  The Atlas V's and Delta IV's that are flying now are not the same as the ones that first flew.  The fact that Atlas V hasn't done a V1 to V1.1 (aside from the re-usability items) means that LM properly selected the engine and tanks sizes in the first place.  But that didn't mean they haven't done upgrades.  There was new avionics, new interstage adapters, helium tanks, etc.

Delta IV upgraded its engine.

Why you quoted cutting away that purposedly underlined word?

I was to quick in posting.  That was my point.  Atlas and Delta are not static.   There are continuous changes.  Just not on the scale of V1 to V1.1.  And also, that is due to the ability to add solids.    But as far as other changes, there is common avionics and common upperstages.

Online RoboGoofers

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #41 on: 10/03/2013 03:01 pm »
I can't see any need to send the same reusable Falcon 9 back up in less than 10 hours, at least before 2030 (and that's optimistic).

At one dragon launch a day for a year, that's 2555 people! They aren't just bales of hay; they need extensive training. Even if they had the hardware, there is no infrastructure to vet and train that many astronauts, and there won't be for a decade at least.

That ignores the fact that there is nowhere to put that many people in space, and designing and constructing a ship or station will also take decades. Constructing, fueling, and provisioning a ship that large to go to mars would probably require multiple launches a day, but there's no way we are sending that many people to mars within the next 40 years.

At the rate they're iterating, it won't be a Falcon 9 1.1 that will be doing any of those launches, so any discussion about sub-24hr turnaround is irrelevant to 1.1.


Online oldAtlas_Eguy

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #42 on: 10/03/2013 04:19 pm »
Yes. Think of the F9R version of the v1.1 (legs added) as a testbed for economics and technical solutions. The real Reusable LV will be the next much larger vehicle that is near fully reusable with small maintenance requirements between launches. This is SpaceX's goal and the F9R version of the v1.1 is just a sign post on the roadmap.

Offline douglas100

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #43 on: 10/03/2013 04:21 pm »
The discussion has moved from v1.1 to future re-usability possibilities very quickly. Rapid re-use has been featured a lot because it's a stated SpaceX goal, but I'm with those who believe that will be unnecessary for quite a while into the future. There are not enough payloads presently to require it.  F9R's viability is about not whether they can turn the vehicle round in 24 hours, but whether its re-use saves money. I think there is a reasonable chance that it will, but it is yet to be proved.

I agree with those who say that tanker flights are the most likely types of missions which would benefit from complete and rapid re-usability. But this is in some future world where human spaceflight beyond LEO is extensive enough to create a demand for such services. It is not at all clear to me how we get from the way things are now to such a world. In such a world you could imagine 24 hour turn round, keeping the vehicle upright for processing and all the various other suggestions posted. But then we are talking about some later generation vehicle, not F9R.

Many of the ideas posted in the last few pages have been posted before (my own included.) And so we go round and round.

« Last Edit: 10/03/2013 04:23 pm by douglas100 »
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Offline Oli

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #44 on: 10/03/2013 04:34 pm »
Needless to say if SpaceX had $20bn to spend it could make a cheaper to produce, more reliable, and more maintenance free rocket than it does now.

Quote from: cambrianera
drive for continuous improvement that is common in consumer design and production, uncommon in aerospace.

It may seem that way because consumer products are often throw away products with low quality which are replaced often (like rockets  ;D ;)). If you sell to businesses, it must last longer and be cheap to maintain.
« Last Edit: 10/03/2013 04:35 pm by Oli »

Offline cambrianera

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #45 on: 10/03/2013 04:46 pm »
Quote from: cambrianera
drive for continuous improvement that is common in consumer design and production, uncommon in aerospace.

It may seem that way because consumer products are often throw away products with low quality which are replaced often (like rockets  ;D ;)). If you sell to businesses, it must last longer and be cheap to maintain.

Try to explain this to RIM (Blackberry!)  :o
Oh to be young again. . .

Offline Oli

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #46 on: 10/03/2013 04:56 pm »
Quote from: cambrianera
Try to explain this to RIM (Blackberry!)

Unfortunately Moore's Law doesn't hold for space propulsion technology, otherwise I would be doing sightseeing in the Andromeda Galaxy right now.  ;)
« Last Edit: 10/03/2013 04:57 pm by Oli »

Online LouScheffer

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #47 on: 10/03/2013 07:15 pm »

1.  USA-193 was a specific event with a spacecraft and not applicable to other scenarios.   The military analyzed one problem.  It is no where close the same thing
Orbital debris studies make little distinction between stages blowing up and collisions.   See, for example, "Determination of Breakup Initial Conditions" by Knight, which states "Collision-induced fragmentations and explosions are both addressed".  If you have evidence to the contrary I'd like to see it.

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2.   Still doesn't account for GTO missions with more than 2 burns.  Also, the second burn may occur at a low altitude but the apogee is higher.
You are right it does not account for missions with burns at higher altitudes; that's why I explicitly said that this perspective applies only to "standard" GTO missions where both burns of the second stage are at low altitude.  The intended apogee is of course irrelevant if the engine explodes at startup.  Even if not, the apogee only affects the debris decay time a little, since almost all the drag occurs at perigee.  And an explosion, or collision, cannot raise the perigee above the altitude where it occurred.

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3.  Wrong again on both accounts.  It is not anywhere close to the same, there are many difference.  And, no, not only are potential explosions are not analyzed, it is almost impossible to do it because of the variation.    Why do you post things that you know nothing about.
It is strange that you say this cannot be analyzed.  There are many papers and computer programs to do exactly that, and have been for many years.  See the paper above, published in 1990, and the 34 other papers that cite it. In fact there is even a review article, covering the various means used to analyze this "Review of Debris-Cloud Modeling Techniques".  See http://arc.aiaa.org/doi/abs/10.2514/3.26798?journalCode=jsr .  As above, these papers tend to treat explosions and collisions very similarly.

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4.  a.  Wrong again.  There are elements of launch vehicle and spacecraft that could self propel such as prop and pressure tanks.   The launch vehicle will break up will have larger intact pieces than a collision.
b.  No, the launch vehicle has denser hardware such as the engine, the thrust section, the payload adapter, etc
Self-propel or not, they cannot raise the perigee above altitude where the explosion occurs.  Even the dense stuff will deorbit quickly with these perigees. And larger fragments are better; that means there are fewer of them, and collision risk depends much more on number than on size.

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The risks and consequences of breakup due to a bad engine start out weigh any benefits in trying to complete the mission.
How can you assert this without estimating, from the best available evidence, what the risks and consequences are?   For the case where the second burn is at low altitude, the risks look small.  In particular, when the USA did this for their ASAT interception of a failing satellite, they concluded the risks were not great, and then experimentally verified their predictions. 

Offline R7

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #48 on: 10/03/2013 07:56 pm »
1.  USA-193 was a specific event with a spacecraft and not applicable to other scenarios.   The military analyzed one problem.  It is no where close the same thing
Orbital debris studies make little distinction between stages blowing up and collisions.   See, for example, "Determination of Breakup Initial Conditions" by Knight, which states "Collision-induced fragmentations and explosions are both addressed".  If you have evidence to the contrary I'd like to see it.

Maybe it isn't about collision vs explosion pressure release event but more about the orbits. If the amateur observations in wiki are correct USA-193 was in ~250km circular orbit. Even big things that low are decaying quickly. Colliding with suborbital kinetic warhead is unlikely (impossible?) to send any debris to longer lasting orbit because major velocity direction change dips perigee even lower, causing faster decay or immediate reentry.

CASSIOPE mission US is in substantially higher and more elliptical ~325x1500km orbit.
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Offline spacejulien

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #49 on: 10/03/2013 08:34 pm »
2.   Still doesn't account for GTO missions with more than 2 burns.  Also, the second burn may occur at a low altitude but the apogee is higher.
You are right it does not account for missions with burns at higher altitudes; that's why I explicitly said that this perspective applies only to "standard" GTO missions where both burns of the second stage are at low altitude.  The intended apogee is of course irrelevant if the engine explodes at startup.  Even if not, the apogee only affects the debris decay time a little, since almost all the drag occurs at perigee.  And an explosion, or collision, cannot raise the perigee above the altitude where it occurred.

Quote
4.  a.  Wrong again.  There are elements of launch vehicle and spacecraft that could self propel such as prop and pressure tanks.   The launch vehicle will break up will have larger intact pieces than a collision.
b.  No, the launch vehicle has denser hardware such as the engine, the thrust section, the payload adapter, etc
Self-propel or not, they cannot raise the perigee above altitude where the explosion occurs.  Even the dense stuff will deorbit quickly with these perigees. And larger fragments are better; that means there are fewer of them, and collision risk depends much more on number than on size.

There is quite a difference between USA-193 which has been intercepted on a specific location on its orbit to an upper stage that may disintegrate anytime along its flight path and orbital elements different depending on the time of breakup and more energy stored on board. So even if debris cloud modelling techniques are the same, your simple transfer of conclusions from USA-193 to disintegrating stages is not at all valid.

Also, orbital mechanics contradicts you: The drag in perigee reduces the height of the apogee. With the apogee very high it takes very long to reduce apogee height until reentry. An expended stage on a "standard" GTO with 250 km perigee  needs 25 years to reenter. That is a long time for a lot of debris to create secondary debris with all the other dead stages on GTO orbits. For a start, you may read this http://www.spacesafetymagazine.com/2013/07/18/compliance-rocket-upper-stage-gto-space-debris-mitigation-guidelines/
« Last Edit: 10/03/2013 08:35 pm by spacejulien »
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Online LouScheffer

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #50 on: 10/03/2013 11:27 pm »

There is quite a difference between USA-193 which has been intercepted on a specific location on its orbit to an upper stage that may disintegrate anytime along its flight path and orbital elements different depending on the time of breakup and more energy stored on board. So even if debris cloud modelling techniques are the same, your simple transfer of conclusions from USA-193 to disintegrating stages is not at all valid.
People keep stating there is a big difference between an explosion and a collision, but all the evidence that's been shown so far tells the opposite story - they are very much the same as far as debris is concerned.  As yet another example, check out "Moderately Elliptical Very Low Orbits (MEVLOs) as a Long Term Solution to Orbital Debris" as an example.   They state, for orbits with perigees 300km of less, and apogees 500 km or less (and all the parking orbits we are talking about here fit these criteria), that "any satellite that explodes, or otherwise dies in this region will not be a part of a long term debris problem".

Quote
Also, orbital mechanics contradicts you: The drag in perigee reduces the height of the apogee. With the apogee very high it takes very long to reduce apogee height until reentry. An expended stage on a "standard" GTO with 250 km perigee  needs 25 years to reenter. That is a long time for a lot of debris to create secondary debris with all the other dead stages on GTO orbits. For a start, you may read this http://www.spacesafetymagazine.com/2013/07/18/compliance-rocket-upper-stage-gto-space-debris-mitigation-guidelines/
Sure, but we are talking about whether the engine should try anyway, for a GTO injection burn, if something looks fishy when it tries to ignite.  This makes the scenerio above unlikely in the extreme.  If the engine does not start, the orbit decays quickly.  If it blows up when it tries to start, the debris re-enters quickly.  If it starts and works OK, you end with the same orbit as a successful mission, with a low perigee to make it re-enter.  You would need a very weird failure mode to get the effect you describe.  The engine would need to start, run quite a while to raise the apogee significantly, deviate from  the intended trajectory, then explode.  Not impossible, but very unlikely.

Online LouScheffer

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #51 on: 10/03/2013 11:45 pm »
1.  USA-193 was a specific event with a spacecraft and not applicable to other scenarios.   The military analyzed one problem.  It is no where close the same thing
Orbital debris studies make little distinction between stages blowing up and collisions.   See, for example, "Determination of Breakup Initial Conditions" by Knight, which states "Collision-induced fragmentations and explosions are both addressed".  If you have evidence to the contrary I'd like to see it.

Maybe it isn't about collision vs explosion pressure release event but more about the orbits. If the amateur observations in wiki are correct USA-193 was in ~250km circular orbit. Even big things that low are decaying quickly. Colliding with suborbital kinetic warhead is unlikely (impossible?) to send any debris to longer lasting orbit because major velocity direction change dips perigee even lower, causing faster decay or immediate reentry.

CASSIOPE mission US is in substantially higher and more elliptical ~325x1500km orbit.
This makes sense.  CASSIOPE was higher and debris would be a bigger concern.  So maybe on that mission they decided to stop if something seemed odd.  On the next mission, a GTO injection, it makes more sense to keep trying anyway since the worst case debris would not be a problem.  However, implementing this would mean different software, or at least different parameters, on the two mission.  This leaves SpaceX with a choice - violate "test as you fly", or accept a failure (with a customer payload) due to overly-tight parameters, when the hardware was perfectly capable of completing the mission.   Neither of these is great, but my current guess is that a violation of "test as you fly" is most likely.  So even though they stopped CASSIOPE second burn due to an out-of-bounds condition, in my opinion on the SES mission they will try to keep going.

Offline Jim

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #52 on: 10/03/2013 11:47 pm »

1.  Orbital debris studies make little distinction between stages blowing up and collisions. 

2.    And an explosion, or collision, cannot raise the perigee above the altitude where it occurred.

3.  It is strange that you say this cannot be analyzed.

4.  Self-propel or not, they cannot raise the perigee above altitude where the explosion occurs.

5.  How can you assert this without estimating, from the best available evidence, what the risks and consequences are?   For the case where the second burn is at low altitude, the risks look small.  In particular, when the USA did this for their ASAT interception of a failing satellite, they concluded the risks were not great, and then experimentally verified their predictions. 
 

1.  It is not the debris, it is the specific occasion that was analyzed.  Routine launches are not analyzed for breakup effects.

2.  Apogee is what matters

3.  That is not strange, what is strange is that you think you know better, when it has been shown to be the opposite.  What can't be analyzed is all the variations of when a break up could occur and subsequent effects.  This is unlike USA-193 which was one specific static orbit and a specific impact location and specific time.

4. Again, apogee matters

5. 
a. The easy answer is  that Occam's razor says it has been done
b. The best available evidence says the risk is high.   The consequences are obviously are high, damage to other spacecraft, with an unplanned breakup (opposite of USA-193 which was planned)
c.  Because your assertion about USA-193 is wrong
d. What qualifications say the risks look small?

Online meekGee

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #53 on: 10/03/2013 11:52 pm »
2.  Apogee is what matters


A low perigee means that orbital decay will be quick, just as was stated.
A high perigee means only that during the limited lifetime of that piece of debris, it will cross higher orbits.

Between these two, the short lifetime is the more important consideration.

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Offline Jim

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #54 on: 10/03/2013 11:57 pm »
1.  On the next mission, a GTO injection, it makes more sense to keep trying anyway since the worst case debris would not be a problem. 

2.  However, implementing this would mean different software, or at least different parameters, on the two mission.  This leaves SpaceX with a choice - violate "test as you fly", or accept a failure (with a customer payload) due to overly-tight parameters, when the hardware was perfectly capable of completing the mission.   Neither of these is great, but my current guess is that a violation of "test as you fly" is most likely. 

3.  So even though they stopped CASSIOPE second burn due to an out-of-bounds condition, in my opinion on the SES mission they will try to keep going.

Sheesh,  Will you listen?  It is like talking to a wall.

1.  Wrong again, it does not make sense to keep trying. The worse case debris would still be a problem  An engine with a rough start does not always go bad quickly, it can provide some impulse to raise the orbit before it goes bad and hence be a danger to other spacecraft

2.  Wrong, that would not be a TLFY violation.  Changing parameters does not qualify.  The software is made with the ability to change parameters.

3.  Huh?  what makes you think they are going to change how they do things?    And as shown, yours doesn't amount to much.

Offline Jim

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #55 on: 10/04/2013 12:00 am »
2.  Apogee is what matters


A low perigee means that orbital decay will be quick, just as was stated.
A high perigee means only that during the limited lifetime of that piece of debris, it will cross higher orbits.

Between these two, the short lifetime is the more important consideration.



Huh?.  No, apogee is the important parameter, because even with a low perigee, orbital lifetime can be long

Online LouScheffer

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #56 on: 10/04/2013 12:41 am »
2.  Apogee is what matters


A low perigee means that orbital decay will be quick, just as was stated.
A high perigee means only that during the limited lifetime of that piece of debris, it will cross higher orbits.

Between these two, the short lifetime is the more important consideration.



Huh?.  No, apogee is the important parameter, because even with a low perigee, orbital lifetime can be long
For orbital decay calculations, perigee is far more important, since that's where the drag occurs.  See, for example, "Orbital Mechanics", p. 189 - http://tinyurl.com/nwz5xvb  [MODIFIED BY MODERATOR FOR SHORT URL]

If the perigee is less that about 200 km, all orbits decay quickly (days/weeks), no matter what the apogee.  If the perigee is above about 600 km, all orbits decay slowly (decades/centuries or longer) no matter what the apogee.  For perigees in the middle, apogee can make a difference, but only if it's really big (like GTO size) since then solar/lunar perturbations become similar in size to the drag component.  However, this combination of small perigees and large apogees happens only on successful (or almost successful) GTO missions.  From collisions and explosions at low altitudes,  the apogee variation is nowhere near GEO height (see this Gabbard plot for a booster explosion - https://en.wikipedia.org/wiki/File:Gabbard_diagram.png ) and the decay time is dominated by the perigee.
« Last Edit: 10/04/2013 02:58 am by meekGee »

Offline Jim

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #57 on: 10/04/2013 01:35 am »
If the perigee is less that about 200 km, all orbits decay quickly (days/weeks),

Weeks is not quickly.  Plenty of time to hit other things.

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #58 on: 10/04/2013 03:14 am »
If the perigee is less that about 200 km, all orbits decay quickly (days/weeks),

Weeks is not quickly.  Plenty of time to hit other things.

Even if weeks and not days, then weeks vs. years is already a factor of 50.

And since the lifetime is determined by drag, the majority of the small debris will die sooner, so overall the lifetime statistics will tend towards days, not weeks.

Lou - thanks for the references.
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Offline Jim

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Re: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 4)
« Reply #59 on: 10/04/2013 03:27 am »

Even if weeks and not days, then weeks vs. years is already a factor of 50.

And since the lifetime is determined by drag, the majority of the small debris will die sooner, so overall the lifetime statistics will tend towards days, not weeks.

Whatever. The consequences of the results of a hard start are still there.

The smart move is not to start an engine if its is outside of the start box
« Last Edit: 10/04/2013 10:58 am by Jim »

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