SpaceX Tuesday...

SpaceX Tuesday...

Author
Discussion

Mojocvh

Original Poster:

16,837 posts

206 months

Saturday 3rd January 2015
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Launch the rocket, release the spacecraft, land the rocket on a boat!

Hah, go for it SpaceX!!

Eric Mc

106,984 posts

209 months

Saturday 3rd January 2015
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This should be interesting.

twin40s

151 posts

199 months

Sunday 4th January 2015
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Lets hope there are no more delays.

It's like Thunderbirds for real.

scubadude

2,614 posts

141 months

Monday 5th January 2015
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Got my fingers crossed for them- it makes so much sense.

I think if they can get the first stage anywhere near the Barge they'll have done well, if they land it up-right they'll deserve a standing ovation.

fadeaway

1,463 posts

170 months

Monday 5th January 2015
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Wow!
Hadn't heard about this and didn't know they were so close to trying with a rocket from a "real" launch. It's very cool.

They're saying the chance of landing this attempt is "50% at best". They're going to try doing this several times this year, each time with a higher % of success as they learn and improve things. Love the way they're developing this system!

More about it here:

http://www.spacex.com/news/2014/12/16/x-marks-spot...

Eric Mc

106,984 posts

209 months

Monday 5th January 2015
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It's a very, very difficult thing to do and I'm not convinced it will work at all - or ever become practical.

Hats off to them for giving it a try.

I still think a sod off parachute (or three) is an easier solution.

Caruso

6,942 posts

200 months

Monday 5th January 2015
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fadeaway said:
Wow!
Hadn't heard about this and didn't know they were so close to trying with a rocket from a "real" launch. It's very cool.

They're saying the chance of landing this attempt is "50% at best". They're going to try doing this several times this year, each time with a higher % of success as they learn and improve things. Love the way they're developing this system!

More about it here:

http://www.spacex.com/news/2014/12/16/x-marks-spot...
Sounds like the difficult bit is improving the landing precision from 10km of previous flights to the 10m range for landing on the platform. No wonder they're only saying 50% chance of success.

Eric Mc

106,984 posts

209 months

Monday 5th January 2015
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Keeping a falling cylinder stable whilst it plummets back to earth is problem number 1 - i.e. preventing it from tumbling. They seem to have cracked that bit.

The second problem is slowing it down to the point where it is essentially stopped in mid air - balancing on its rocket exhaust.

The third problem is ensuring the guidance brings it back to a pinpoint spot i.e. the landing barge.

It's a tough set of parameters they have to meet.

Mojocvh

Original Poster:

16,837 posts

206 months

Monday 5th January 2015
quotequote all
Eric Mc said:
Keeping a falling cylinder stable whilst it plummets back to earth is problem number 1 - i.e. preventing it from tumbling. They seem to have cracked that bit.

The second problem is slowing it down to the point where it is essentially stopped in mid air - balancing on its rocket exhaust.

The third problem is ensuring the guidance brings it back to a pinpoint spot i.e. the landing barge.

It's a tough set of parameters they have to meet.
Yes agreed Eric, but this video is just amazing....earlier tests including the hover and return to pad.

https://www.youtube.com/watch?v=0UjWqQPWmsY


Caruso

6,942 posts

200 months

Monday 5th January 2015
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Spaceflight now is reporting a 40% chance of a delay till Friday due to weather.

CrutyRammers

9,397 posts

142 months

Monday 5th January 2015
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Eric Mc said:
Keeping a falling cylinder stable whilst it plummets back to earth is problem number 1 - i.e. preventing it from tumbling. They seem to have cracked that bit.

The second problem is slowing it down to the point where it is essentially stopped in mid air - balancing on its rocket exhaust.

The third problem is ensuring the guidance brings it back to a pinpoint spot i.e. the landing barge.

It's a tough set of parameters they have to meet.
And last but not least, doing it in a cost-effective way...

Simpo Two

69,944 posts

209 months

Monday 5th January 2015
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Eric Mc said:
Keeping a falling cylinder stable whilst it plummets back to earth is problem number 1 - i.e. preventing it from tumbling. They seem to have cracked that bit.

The second problem is slowing it down to the point where it is essentially stopped in mid air - balancing on its rocket exhaust.

The third problem is ensuring the guidance brings it back to a pinpoint spot i.e. the landing barge
They were doing this all the time in 1950's sci-fi films!

I still think that trying to land backwards on a tiny floating platform is making a difficult thing just about impossible. Maybe they'll add boxing gloves on springs too.


Eric Mc

106,984 posts

209 months

Monday 5th January 2015
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Mojocvh said:
Yes agreed Eric, but this video is just amazing....earlier tests including the hover and return to pad.

https://www.youtube.com/watch?v=0UjWqQPWmsY
It's getting the thing slowed down enough from its fall from 30 odd miles up that I think is the REALLY hard part. Once you've got it down to a falling velocity of around 20 mph you are almost there.

Mojocvh

Original Poster:

16,837 posts

206 months

Monday 5th January 2015
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Eric Mc said:
Mojocvh said:
Yes agreed Eric, but this video is just amazing....earlier tests including the hover and return to pad.

https://www.youtube.com/watch?v=0UjWqQPWmsY
It's getting the thing slowed down enough from its fall from 30 odd miles up that I think is the REALLY hard part. Once you've got it down to a falling velocity of around 20 mph you are almost there.
Good point Eric, if using the engines all the way they will need fuel to do so. So it will have to take it[the fuel] with it.

Hmm..First Texaco "station" in orbit??

Eric Mc

106,984 posts

209 months

Monday 5th January 2015
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It's all about compromises.

The Space Shuttle carried the dead weight of wings, tailfin and undercarriage components all the way into orbit - and the substantially larger amount of fuel required to lift those wings, tailfin and undercarriage bits into orbit - just so it could fly back to a runway landing.

Because of the criticalness of maintaining a correct centre of gravity and centre of lift for all flight regimes from Mach 25 down to 200 knots, the Shuttle often had to carry lead ballast in its cargo bay just to ensure that the centre of gravity and lift were within tolerances. Otherwise it would have been impossible to fly - even with fly-by-wire.

As far as SpaceX is concerned, I still think a bloody great set of parachutes would do the trick in a far less complex way.

MartG

14,417 posts

148 months

Monday 5th January 2015
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Eric Mc said:
As far as SpaceX is concerned, I still think a bloody great set of parachutes would do the trick in a far less complex way.
Though how would you steer the descending stage to a precision landing using parachutes ? Given where they are launching from and hence where it will come down ( i.e. in the Atlantic Ocean ), there is a severe shortage of large expanses of land on which it could touchdown so the precision of a powered landing is required

Eric Mc

106,984 posts

209 months

Monday 5th January 2015
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What is the problem with gentle plop into the ocean?

I am sure they could get the accuracy to within a couple of hundred yards of a recovery vessel. If the vessel had a bespoke lifting device on it, they could have it out of the water in less than an hour.

I expect they are probably concerned about the issue of the effect of salt water on the rocket motors - and to be honest - that was the main reason why NASA

a) gave up on the idea of recovering the 1st stages of Saturn IBs and Saturn Vs

b) chose Solid Rockets for the Shuttle programme

Toaster

2,729 posts

137 months

Monday 5th January 2015
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Eric Mc said:
It's all about compromises.

The Space Shuttle carried the dead weight of wings, tailfin and undercarriage components all the way into orbit - and the substantially larger amount of fuel required to lift those wings, tailfin and undercarriage bits into orbit - just so it could fly back to a runway landing.

Because of the criticalness of maintaining a correct centre of gravity and centre of lift for all flight regimes from Mach 25 down to 200 knots, the Shuttle often had to carry lead ballast in its cargo bay just to ensure that the centre of gravity and lift were within tolerances. Otherwise it would have been impossible to fly - even with fly-by-wire.

As far as SpaceX is concerned, I still think a bloody great set of parachutes would do the trick in a far less complex way.
Point 1 you make is why Virgin Galactic in its current state will never be more than a fairground ride wink

Aircraft also maintain trim by moving fuel around

I don't disagree regarding the parachutes, but its been done before with the LEM in the 60's from around 61nm (from Mach 4.8 to 0 knots) and other landing craft such as mars curiosity rover although the latter did have a heat shield and parachute.

The question is how practical is this you use one shed load of fuel to launch and a heap more to slow it down.


scubadude

2,614 posts

141 months

Monday 5th January 2015
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Eric Mc said:
What is the problem with gentle plop into the ocean?

I am sure they could get the accuracy to within a couple of hundred yards of a recovery vessel. If the vessel had a bespoke lifting device on it, they could have it out of the water in less than an hour.

I expect they are probably concerned about the issue of the effect of salt water on the rocket motors - and to be honest - that was the main reason why NASA

a) gave up on the idea of recovering the 1st stages of Saturn IBs and Saturn Vs

b) chose Solid Rockets for the Shuttle programme
I believe the end goal is landing on dry land, the barge is just a stop gap till they can actually land where they want.

As far as I understand it the legs, grid fins + "abit" of fuel combo is Slightly lighter than big F-off parachutes which you would need additional fuel to loft anyway, its one of those balance of sums type situations.

The previous flight test got it to upright, almost dead stop but ended with a "gentle plop into the ocean" for safety- this is more a test of guidance now.

MartG

14,417 posts

148 months

Monday 5th January 2015
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Eric Mc said:
What is the problem with gentle plop into the ocean?
They did that on the last couple of flights - touching down with zero velocity - both times the stage was then destroyed by the impact with the sea when it fell over. A parachute landing would probably be even less gentle.

The only 'stages' so far recovered intact at sea after a parachute landing were the Shuttle SRBs, which have a lot more robust structure than a lightweight liquid fuelled stage.