Author Topic: Well done SpaceX  (Read 23320 times)

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Offline coppice

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Re: Well done SpaceX
« Reply #25 on: January 14, 2016, 01:46:23 am »
The big issue with solid fuels is you cannot throttle. Once ignited, they keep burning with whatever profile you designed them with for the most part.
That is a big issue for small systems, but not such a big issue for large systems with multiple motors. Systems like the space shuttle have used cheap refillable solid boosters to do most of the grunt cheaply, and an expensive liquid fuelled motor to do the fine adjustments.
« Last Edit: January 14, 2016, 02:27:17 am by coppice »
 

Offline mtdoc

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Re: Well done SpaceX
« Reply #26 on: January 14, 2016, 01:50:48 am »
No manned mission to Mars unless a rocket can be landed and later reignited, right?
 

Offline Brumby

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Re: Well done SpaceX
« Reply #27 on: January 14, 2016, 01:54:30 am »
Maybe later - but I was under the impression that the first human mission to Mars was a one-way trip.

Or is that not the case?
 

Offline edavid

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Re: Well done SpaceX
« Reply #28 on: January 14, 2016, 02:26:00 am »
No manned mission to Mars unless a rocket can be landed and later reignited, right?

Solid fuel engines are only used to boost rockets from Earth, where it's no problem to just use them up (except in abort cases).  Higher stage and return vehicle engines are always liquid fueled.
 

Offline edavid

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Re: Well done SpaceX
« Reply #29 on: January 14, 2016, 02:27:10 am »
Maybe later - but I was under the impression that the first human mission to Mars was a one-way trip.

Or is that not the case?

Highly unlikely.  Keeping the crew alive on Mars indefinitely is probably harder than bringing them back.
 

Offline free_electron

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Re: Well done SpaceX
« Reply #30 on: January 14, 2016, 04:08:41 am »
For everyone on the launching pad, the cost is about 1/3 the rocket, 1/3 the payload, and 1/3 insurance. Figure from early 1990s.

- The launching company does not own the payload.
- the insurance is always there.

so, for the launcher the material cost can be reduced to the fuel only and some consumables.
the rocket costs more to develop but this is amortized over the number of flights. even if it costs 50% more to develop after one reuse you are in the clear.

Falcon has trust vectoring capabilities. Just like grashopper. It can hover and fly sideways.
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Offline CatalinaWOW

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Re: Well done SpaceX
« Reply #31 on: January 14, 2016, 05:43:06 am »
The devil is in the details.  As Musk says, they are going over the recovered rocket seeing if it is indeed re-usable.  What parts will need to be replaced.  What will need to be made more robust.  Reusability costs payload for both the fuel and hardware required for return.  If the costs of refurbishment are high, or if the mass cost of making refurbishment cheap are high it will make no sense.

The space shuttle was supposed to reduce launch costs through reusability.  When the actual costs of refurbishment for flight (under NASA rules) came in it was at best a wash.  Then there was a fad for cheap throwaway launchers.  When the costs came in for lost payloads there wasn't much if any savings.  So we will have to see if SpaceX can actually make a difference.  There is good reason to hope.  Lots of bright people, lots of new materials and electronics technology to work with, and maybe even a dash of efficiency from commercial development.  But spaceflight is really hard.  So it may take a few more rounds of development to get there.
 

Offline HP-ILnerd

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Re: Well done SpaceX
« Reply #32 on: January 14, 2016, 10:15:24 pm »
Some things worth noting (and general comments on points made above):

Even though it cost SpaceX more to develop reusability to this state, they still offer the lowest cost per pound to orbit in the industry even without reuse.  Even the Chinese can't beat their price.  Falcon Heavy will cut the Falcon 9 price more than in half.

SpaceX is not taking an expendable booster and trying to see if it can be reused.  It was engineered to be reusable right away, as best they could do.  The actual procedures and requirements for doing this are what the test program has been about.  When they first started trying to re-enter the 1st stage, they couldn't even keep it from shredding in the supersonic wind.  Many incremental refinements followed.  They are obviously making progress.

There are no boosters of any size that do not have thrust vectoring.  Gimballed nozzles are used even on solid-motor ICBMs.  One such can be seen here:


Most of the DeltaV to orbit from the booster (regardless of destination) comes from the second stage.  Typically in the vicinity of 4/5ths.  The first stage just gets you past the "knee" in the rocket equation graph.  Despite this, it's still the most expensive part of the vehicle, due to it's size and the fact that 90% of the engines on an F9 are in the first stage.

The Space Shuttle was expensive because everyone from Apollo kept their job.  A typical US Government "save the civil servants" operation.  It took an army of 30,000 employees to get that thing serviced, turned around, re-stacked and launched.  It stretched the definition of reusability to the breaking point.  Even the cockpit windows had to be unmounted and sent back to the manufacturer for polishing off micrometeoroid damage between flights.  SpaceX has an order of magnitude fewer employees than Shuttle alone required, and couldn't spend money like that if they tried.

There is no question that the Merlin motor can be reused and restarted.  The first stage undergoes a full flight duration hotfire on a test stand in Texas before it's sent to the cape.  http://www.spacex.com/about/capabilities.  So the motors used in any flight (expendable or otherwise) are already being reused.  To land the recent booster required the launch burn, a boost back burn, an entry burn then a landing burn (4 separate engine starts).

Later this year, we could well be treated to seeing this:
 

Offline dannyf

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Re: Well done SpaceX
« Reply #33 on: January 14, 2016, 10:37:09 pm »
"Even though it cost SpaceX more to develop reusability to this state, they still offer the lowest cost per pound to orbit in the industry even without reuse.  Even the Chinese can't beat their price.  Falcon Heavy will cut the Falcon 9 price more than in half."

I would say that slightly differently. Musk is not nproven at this point. Umtil he can deliver the same economics as promised after 20 or 30 launches, you have to take his words with a grain of salt.

The fact that no one else is developing reusable rockets makes me wonder about his claims.

Again, I think landing a rocket itself is not that big a deal. It is the capabilities that enables that landing (thruttle control and potentially reignitable solid fuel rockets) and their potential military applications that are far more valuable. Ie. Even if reusable rockets turn out to a commercial failure, space itself can still be a huge success.
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Offline tom66

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Re: Well done SpaceX
« Reply #34 on: January 14, 2016, 10:48:53 pm »
SpaceX is betting on the demand side of rocket launches being very elastic, which should mean lower price = more launches. I am not certain it will play out that way. I think the reality is likely to be somewhat less, as satellites still cost a lot, but this might bring changes to the market are hard to foresee. For example much cheaper satellites, if the rocket cost is no longer significant.

AFAIK the rockets start paying off about 4-5 flights in because of the additional hardware, logistics, and fuel required (all mean lost payload). If the rocket survives its first flight with only minor wear I can't see why 20+ flights per rocket isn't possible.  And even if there is increased risk this may well be covered by the lower launch costs.
 

Offline HP-ILnerd

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Re: Well done SpaceX
« Reply #35 on: January 14, 2016, 11:13:42 pm »

The fact that no one else is developing reusable rockets makes me wonder about his claims.

Again, I think landing a rocket itself is not that big a deal. It is the capabilities that enables that landing (thruttle control and potentially reignitable solid fuel rockets) and their potential military applications that are far more valuable. Ie. Even if reusable rockets turn out to a commercial failure, space itself can still be a huge success.

Fact?   Does ULA count?  http://spaceflightnow.com/2015/04/13/ula-unveils-its-future-with-the-vulcan-rocket-family/ 
Blue Origin?  https://www.blueorigin.com/technology
Skylon? http://www.reactionengines.co.uk/space_skylon.html
ESA?  http://spacenews.com/meet-adeline-airbus-response-to-reusable-spacex-rocket/
Russia?  http://www.space.com/18046-russia-reusable-rockets-2020.html

That's a long list with "no one" on it.  :)

 

Offline HP-ILnerd

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Re: Well done SpaceX
« Reply #36 on: January 14, 2016, 11:53:39 pm »
Update on the ISS SpaceX/Orbital/Sierra/Boeing cargo contract:

http://www.bloomberg.com/news/articles/2016-01-14/musk-s-spacex-splits-nasa-contracts-with-orbital-sierra-nevada

It's hard to believe the Boeing/Lockmart got left out in the cold on this one.  Mighta been the Russian motor issue.  I'm happy to see Sierra wasn't left out.
 

Offline tom66

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Re: Well done SpaceX
« Reply #37 on: January 18, 2016, 04:03:51 am »
Close...but no cigar

Topples over after "landing". Looks like a leg didn't latch properly. Damn close though.

 

Offline CatalinaWOW

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Re: Well done SpaceX
« Reply #38 on: January 18, 2016, 04:19:20 am »
Just about there.  If this was easy it would have been done years ago.  They are so close they can taste it.
 

Online BradC

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Re: Well done SpaceX
« Reply #39 on: January 18, 2016, 04:42:09 am »
Still a significant difference between "fell over" and "total loss".

This is far better than any of the so-called "reality tv" shows, so keep it coming!
 

Offline Galenbo

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Re: Well done SpaceX
« Reply #40 on: January 18, 2016, 08:59:55 am »
Man, this is cool.   ;D

I have a difficult time understanding the real impact of this. Seems more of a gimmick.

I don't understand it.

A global banker makes nuclear powered cars, so he can use all fossil fuel to burn in rockets, and then makes a Kim-Jong-Un style video about it (2:18) where everyone is payed to applaude on command.

But it must be me. Misprogrammed, I guess.
« Last Edit: January 18, 2016, 09:08:34 am by Galenbo »
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Offline miguelvp

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Re: Well done SpaceX
« Reply #41 on: January 18, 2016, 09:46:10 am »
...and then makes a Kim-Jong-Un style video about it (2:18) where everyone is payed to applaude on command.

But it must be me. Misprogrammed, I guess.

Must be you, they were being paid regardless of how proud they were for getting the job done.

Are you seriously connecting SpaceX to Kim Jong Un?
 

Offline Gyro

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Re: Well done SpaceX
« Reply #42 on: January 18, 2016, 10:17:28 am »
Close...but no cigar

Topples over after "landing". Looks like a leg didn't latch properly. Damn close though.



The earlier part of the coverage showed fairly rough sea and the barge rolling quite a bit. Not sure I'd have wanted to land something that tall on a platform like that!  :scared:
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Offline MrSlack

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Re: Well done SpaceX
« Reply #43 on: January 18, 2016, 10:34:43 am »
Money shot:


Good try! They will get there in the end. I read somewhere they reckon it may have been due to ice on the platform.
 

Offline coppice

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Re: Well done SpaceX
« Reply #44 on: January 18, 2016, 12:46:56 pm »
Close...but no cigar
Topples over after "landing". Looks like a leg didn't latch properly. Damn close though.

The earlier part of the coverage showed fairly rough sea and the barge rolling quite a bit. Not sure I'd have wanted to land something that tall on a platform like that!  :scared:
That's a pretty normal sea. If their barge can't maintain adequate stability like that, they need a new barge.
 

Offline Nerull

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Re: Well done SpaceX
« Reply #45 on: January 18, 2016, 12:57:51 pm »
I suspect that the whole reusable rocket thing is less about lowering costs for commercial launches but more about getting potential military contracts / applications.

For Musk to be able to reland a rocket (from orbit), he must have been able to control thrust (just trust, not thrust vectoring), potentially reignitable rockets.

Reignitable rocket engines would allow satellites to be repositioned while in orbit, making them difficult to be destroyed by anti-satellite missiles. It would also make possible in-orbit / standby missiles that can greatly reduce the time for them to be deployed, making them less likely to be intercepted. Or it could be mounted on re-entry vehicles, ...

First: The falcon 9 first stage is not returning from orbit. Not even close.

Second: This is a problem that has been solved for decades. Most liquid fueled rocket engines can be throttled, since vehicle acceleration increases rapidly as fuel mass drops and its highly desirable to control G forces and aerodynamic loads during launch - this is a problem that was solved a long time ago. Most upper stages are re-ignitable, because most geostationary launch profiles include a coast period between LEO and GTO. Its also highly desirable for an upper stage to be capable of deorbiting itself after payload deployment, to avoid contributing to space junk. Satellites already have maneuvering thrusters, and they already reposition themselves. Geostationary satellites are pretty regularly moved around as needed, and there are often on-orbit spares ready to move into place of any failed satellite. LEO constellations like Iridium also have on-orbit spares, ready to move into position as needed. Satellites in LEO must regularly perform orbit corrections due to atmospheric drag, so they need thrusters too. In fact, you'd be hard pressed to find a satellite that doesn't already have a maneuvering system, unless its only designed for very short term operations.

Learning the first detail about spaceflight might help, if you're going to offer opinions as to why SpaceX is doing what it is doing. Restartable engines, throttling, gimbaled engines, maneuvering thrusters - stuff we've been doing since the 60s - is not the reason.

What's next, he's developing electric cars not because he thinks they're a good idea but because the military might be interest in this technology called the wheel? You managed to name all the least impressive things SpaceX has accomplished.

Note: This is in no way meant to detract from what SpaceX has accomplished, its purely a response to ignorant speculation about developing new tech everyone already had.
« Last Edit: January 18, 2016, 01:19:00 pm by Nerull »
 

Offline mtdoc

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Re: Well done SpaceX
« Reply #46 on: January 18, 2016, 06:00:20 pm »
Money shot:


Good try! They will get there in the end. I read somewhere they reckon it may have been due to ice on the platform.

That is not the most recent landing though, is it.  Good try indeed...
 

Offline ajb

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Re: Well done SpaceX
« Reply #47 on: January 18, 2016, 06:40:59 pm »
Money shot:


Good try! They will get there in the end. I read somewhere they reckon it may have been due to ice on the platform.

That is not the most recent landing though, is it.  Good try indeed...

No, it is the most recent (2016-01-17).  I was watching the live webcast, and just as the orange glow was appeared on the far side of the landing ship the satellite feed cut out  |O.  When they first learned of the RUD, they thought they had a hard landing, but once the telemetry and video came in it appears the landing itself was nominal, but the one landing leg failed to lock open.

What's next, he's developing electric cars not because he thinks they're a good idea but because the military might be interest in this technology called the wheel? You managed to name all the least impressive things SpaceX has accomplished.

Indeed.  Most of the technology SpaceX has developed is evolutionary, and you can draw a pretty clear line from the rockets of 50-60 years ago to the Falcon family, with a few nice boosts along the way from modern design, analysis, and fabrication techniques.  That doesn't make it any less awe-inspiring, mind, but it's important to understand the company in its proper context.  What is revolutionary about Space X is that they've been doing everything with an unprecedented speed and leanness that NASA, with its projects perpetually mired in Congressional politics, can only dream of.  Part of that has been enabled by much better design and fabrication technologies, part of it is the private capital, and part of it is surely company culture and Elon Musk himself.  Whatever the cause, the aerospace landscape has already been remade by SpaceX's success to date--look at who NASA is buying transport from these days!--and the potential cost savings from a fully reusable first stage will drastically change the economics of space by lowering the barrier to entry. 

How, exactly, that all shakes out remains to be seen, but it's an exciting time.
« Last Edit: January 18, 2016, 08:12:14 pm by ajb »
 

Offline dannyf

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Re: Well done SpaceX
« Reply #48 on: January 18, 2016, 07:11:56 pm »
Quote
What is r[/u]evolutionary about Space X is that they've been doing everything with an unprecedented speed and leanness that NASA, with its projects perpetually mired in Congressional politics, can only dream of.

Two things to consider:

1) NASA has a different mission than Musk;
2) NASA has a track record to speak of. Musk has none.

So it is difficult to compare Musk vs. NASA as the two are incomparable, until Musk has delivered a performance comparable to NASA's.

Musk has a lot going for him, the re-ignitable rockets and thrust control for example are ground breaking stuff - no one has pulled it off before and it has a significant potential.

Whether the reusable rockets make sense is not clear, as we have too little information to make reliable assessment from.
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Offline CatalinaWOW

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Re: Well done SpaceX
« Reply #49 on: January 18, 2016, 11:16:15 pm »
Quote
What is r[/u]evolutionary about Space X is that they've been doing everything with an unprecedented speed and leanness that NASA, with its projects perpetually mired in Congressional politics, can only dream of.

Two things to consider:

1) NASA has a different mission than Musk;
2) NASA has a track record to speak of. Musk has none.


NASA could do a lot better if it had one mission and it didn't change every 4-8 years.  Is their mission earth observation, moon colonization, a visit to mars, an asteroid rondezvous, protection from asteroids, commercialization of space, or demonstration of core technologies for later use by industry?  All of these have been brought to the front over the last 50 years, and then reversed or dropped in priority when a new administration comes along.

NASAs track record is reflective of the above.  They have launched a lot of stuff into orbit.  And blown a lot of stuff up on the way up or the way back.  Had a lot of successful missions.  Had quite a few failures.  And pulled some amazing rabbits out of the hat.  Apollo XIII, Spacelab and the Hubble Space telescope were all on path to be spectacular failures that were brilliantly recovered by NASA. 

Musk has a much shorter record, but it compares very well with NASAs start.  It is hard to compare the first years of NASA with Musks first years because the techologies and unknowns are different, but NASA had a very rocky start.  Had to have a lot of help from the Army to actually get into space.  Embarassed everybody since NASA was supposed to be the civilian, peaceful space program and they kept blowing up on the pad.
 


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