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Successful flight by Blue Origin



 
 
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  #11  
Old April 6th 16, 10:30 PM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
Thomas Koenig
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Posts: 47
Default Successful flight by Blue Origin

Robert Clark schrieb:

SpaceX needs to stop trying to reinvent the wheel, and investigate means of
giving the F9 hovering capability.


One second of hovering costs 9.81 m/s of delta v.

If your aim is to achieve orbit with a reusable rocket and a reasonable
payload, you need to save as much delta v as possible.

If you aim is to ferry up tourists for a few minutes of zero g, you
don't need to economize as much.

Both choices are reasonable for what the respective companies want to
do.
  #12  
Old April 7th 16, 11:07 AM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
Jeff Findley[_6_]
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Posts: 2,307
Default Successful flight by Blue Origin

In article ,
says...

Robert Clark schrieb:

SpaceX needs to stop trying to reinvent the wheel, and investigate means of
giving the F9 hovering capability.


One second of hovering costs 9.81 m/s of delta v.


Yes, but hovering an almost empty first stage with no payload on top
requires far less fuel and oxidizer than launch. Note that only one
(the center engine) out of nine of the first stage engines are used for
landing. On top of that, the engine is throttled down as much as it can
be. So, fuel consumption upon landing is far, far less than during
launch.

If your aim is to achieve orbit with a reusable rocket and a reasonable
payload, you need to save as much delta v as possible.


Or make everything, but the payload, bigger.

If you aim is to ferry up tourists for a few minutes of zero g, you
don't need to economize as much.


This is because a sub-orbital hop requires far less delta-V than
attaining orbital velocity.

Both choices are reasonable for what the respective companies want to
do.


They're reasonable if they work. SpaceX is trying to avoid adding other
engines to the Falcon 9 first stage. The stage could hover and land,
for example, if it added Super Draco engines to the first stage. But,
they require different fuel and oxidizer than the first stage carries.
This would mean adding completely different tanks, plumbing, and etc.
for those engines. Also, if Super Dracos were used, it would be
advantageous to deplete the kerosene and then vent any remaining LOX in
the tanks before landing. So, any "leftover" fuel and oxidizer would be
"wasted". In my book, this would not be a good trade to make.

All of that added complexity and added mass would cost money compared to
using "leftover" fuel and oxidizer and an engine that is already there
for launch.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #13  
Old April 7th 16, 06:43 PM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
Rick Jones[_6_]
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Posts: 106
Default Successful flight by Blue Origin

In sci.space.policy Jeff Findley wrote:
They're reasonable if they work. SpaceX is trying to avoid adding
other engines to the Falcon 9 first stage. The stage could hover
and land, for example, if it added Super Draco engines to the first
stage. But, they require different fuel and oxidizer than the first
stage carries. This would mean adding completely different tanks,
plumbing, and etc. for those engines. Also, if Super Dracos were
used, it would be advantageous to deplete the kerosene and then vent
any remaining LOX in the tanks before landing. So, any "leftover"
fuel and oxidizer would be "wasted". In my book, this would not be
a good trade to make.


If one wanted to give the Falcon 9 first stage the ability to hover,
wouldn't the most straightforward way to do that be create a
deeply-throttled Merlin?

rick jones
--
a wide gulf separates "what if" from "if only"
these opinions are mine, all mine; HPE might not want them anyway...
feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH...
  #14  
Old April 8th 16, 04:41 PM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
Thomas Womack
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Posts: 206
Default Successful flight by Blue Origin

In article ,
Fred J. McCall wrote:

Nothing says you have to use the full capacity of the booster for
payload. Fuel is cheap. Hardware is expensive.


I think there's quite an interesting question as to what you can do
with, say, launches which cost a million dollars and which put
precisely one ton in a 1m x 1m x 2m volume into LEO. It's certainly
not straightforward and I'd be unsure whether it's possible to put
into one ton enough of a spacecraft to be able to rendezvous with
something else and attach the remaining payload to it.

Obviously the first priority would be to get something assembled which
is large enough to stay on orbit indefinitely, do all the difficult
bits of the rendezvous, and let you make the small spacecraft as
stupid as possible.

Almost every imaginable space concept was designed by bored graduate
students in the sixties, I'd be quite intrigued to see how little you
have to bolt around a quantity of liquid xenon to make it reasonable
for some other spacecraft to collect and transfer to its own internal
tankage the liquid xenon.

Tom
  #15  
Old April 8th 16, 11:26 PM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
Jeff Findley[_6_]
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Posts: 2,307
Default Successful flight by Blue Origin

In article ,
says...

Rick Jones wrote:

In sci.space.policy Jeff Findley wrote:
They're reasonable if they work. SpaceX is trying to avoid adding
other engines to the Falcon 9 first stage. The stage could hover
and land, for example, if it added Super Draco engines to the first
stage. But, they require different fuel and oxidizer than the first
stage carries. This would mean adding completely different tanks,
plumbing, and etc. for those engines. Also, if Super Dracos were
used, it would be advantageous to deplete the kerosene and then vent
any remaining LOX in the tanks before landing. So, any "leftover"
fuel and oxidizer would be "wasted". In my book, this would not be
a good trade to make.


If one wanted to give the Falcon 9 first stage the ability to hover,
wouldn't the most straightforward way to do that be create a
deeply-throttled Merlin?


Straightforward, perhaps, but it's a very big design change so you
start with having to requalify as if it's a whole new engine.


And today's successful barge landing proves they don't *need* to hover!

http://www.theverge.com/2016/4/8/113...uccess-falcon-
9-rocket-barge-at-sea

I watched it live and it looked like a very nice landing.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #16  
Old April 8th 16, 11:27 PM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
Jeff Findley[_6_]
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Posts: 2,307
Default Successful flight by Blue Origin

In article ,
says...

Jeff Findley wrote:

In article ,
says...

Robert Clark schrieb:

SpaceX needs to stop trying to reinvent the wheel, and investigate means of
giving the F9 hovering capability.

One second of hovering costs 9.81 m/s of delta v.


Yes, but hovering an almost empty first stage with no payload on top
requires far less fuel and oxidizer than launch. Note that only one
(the center engine) out of nine of the first stage engines are used for
landing. On top of that, the engine is throttled down as much as it can
be. So, fuel consumption upon landing is far, far less than during
launch.


SpaceX plans to reserve about 10% of the fuel load to get the first
stage back down. If someone needs more payload than that calculation
allows, they will have to buy off the booster because it will be
expended. That's going to be MUCH more expensive, so people are going
to size their loads to not require it.

Nothing says you have to use the full capacity of the booster for
payload. Fuel is cheap. Hardware is expensive.


Agreed. And if Falcon 9 is too small, buy a Falcon Heavy launch,
assuming that its development progresses this year.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #17  
Old April 9th 16, 12:13 AM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
[email protected]
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Posts: 1,346
Default Successful flight by Blue Origin

In sci.physics Fred J. McCall wrote:
Rick Jones wrote:

In sci.space.policy Jeff Findley wrote:
They're reasonable if they work. SpaceX is trying to avoid adding
other engines to the Falcon 9 first stage. The stage could hover
and land, for example, if it added Super Draco engines to the first
stage. But, they require different fuel and oxidizer than the first
stage carries. This would mean adding completely different tanks,
plumbing, and etc. for those engines. Also, if Super Dracos were
used, it would be advantageous to deplete the kerosene and then vent
any remaining LOX in the tanks before landing. So, any "leftover"
fuel and oxidizer would be "wasted". In my book, this would not be
a good trade to make.


If one wanted to give the Falcon 9 first stage the ability to hover,
wouldn't the most straightforward way to do that be create a
deeply-throttled Merlin?


Straightforward, perhaps, but it's a very big design change so you
start with having to requalify as if it's a whole new engine.


Yet you were just saying in another thread space stuff doesn't have
bureaucrat bull****.


--
Jim Pennino
  #18  
Old April 9th 16, 07:27 AM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
[email protected]
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Posts: 1,346
Default Successful flight by Blue Origin

In sci.physics Fred J. McCall wrote:
wrote:

In sci.physics Fred J. McCall wrote:
Rick Jones wrote:

In sci.space.policy Jeff Findley wrote:
They're reasonable if they work. SpaceX is trying to avoid adding
other engines to the Falcon 9 first stage. The stage could hover
and land, for example, if it added Super Draco engines to the first
stage. But, they require different fuel and oxidizer than the first
stage carries. This would mean adding completely different tanks,
plumbing, and etc. for those engines. Also, if Super Dracos were
used, it would be advantageous to deplete the kerosene and then vent
any remaining LOX in the tanks before landing. So, any "leftover"
fuel and oxidizer would be "wasted". In my book, this would not be
a good trade to make.

If one wanted to give the Falcon 9 first stage the ability to hover,
wouldn't the most straightforward way to do that be create a
deeply-throttled Merlin?


Straightforward, perhaps, but it's a very big design change so you
start with having to requalify as if it's a whole new engine.


Yet you were just saying in another thread space stuff doesn't have
bureaucrat bull****.


Cite?


Sure, it was by someone called Fred J. McCall talking about nuclear
reactors on Mars being cheap for lack of bureaucrat bull****.


--
Jim Pennino
  #19  
Old April 9th 16, 06:29 PM posted to sci.space.policy
William Mook[_2_]
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Posts: 3,840
Default Successful flight by Blue Origin

On Thursday, April 7, 2016 at 10:07:22 PM UTC+12, Jeff Findley wrote:
In article ,
says...

Robert Clark schrieb:

SpaceX needs to stop trying to reinvent the wheel, and investigate means of
giving the F9 hovering capability.


One second of hovering costs 9.81 m/s of delta v.


Yes, but hovering an almost empty first stage with no payload on top
requires far less fuel and oxidizer than launch. Note that only one
(the center engine) out of nine of the first stage engines are used for
landing. On top of that, the engine is throttled down as much as it can
be. So, fuel consumption upon landing is far, far less than during
launch.


The empty stage weight is around 4.6% of its take off weight. Its terminal velocity is about 0.1 km/sec. The exhaust velocity of the Draco engines is about 3.1 km/sec at sea level. So, to impart 0.15 km/sec to the vehicle, to be assured of bringing it to rest at zero speed and zero altitude, requires

u = 1 - 1/exp(0.15/3.10) = 0.04724

Which means 4.8% of the dead weight starting out must be propellant. This means that 95.2% of the weight is inert in the landing stage.

Now, if 4.6% of the take off weight is inert, then 0.046/0.952 = 0.0483 is the total weight allocated at launch for both inert weight AND propellant required to land it effectively. Or 0.23% of the take off weight.

So a Falcon masses 541,300 kg at lift off. 4.6% of this or 24,900 kg is inert first stage mass. After re-entry, it is travelling about 0.1 km/sec (224 mph) terminal velocity. We must impart a delta vee of 0.15 km/sec (336 mph) to be assured of bringing it to rest at the platform. This requires 1,245 kg of propellant be held in reserve for this purpose. 53,000 kg of thrust are required to exert 2 gees on the empty stage. This is provided by four super draco units of the type shown here

https://en.wikipedia.org/wiki/SuperD...789102495).jpg

1,245 kg of propellant is similar to the propellant loading on the Dragon V2 capsule. Divided among four modules its 311.25 kg each. A tank smaller than the engines.

Basically, this is a variant of the same damned system that brings back the capsule and lands it softly.

https://www.youtube.com/watch?v=WotVw5FDVHY

The only difference is that the first stage recovery is an inverted pendulum.

https://www.youtube.com/watch?v=15DIidigArA


If your aim is to achieve orbit with a reusable rocket and a reasonable
payload, you need to save as much delta v as possible.


Or make everything, but the payload, bigger.


The hardware, software, and propellant weights, are negligible. The savings in cost are not. Gathering propellant from a shaking nearly empty tank, and throttling it back and maintaining positive control during descent, is a challenge, and reduces booster performance in other ways.

If you aim is to ferry up tourists for a few minutes of zero g, you
don't need to economize as much.


This is because a sub-orbital hop requires far less delta-V than
attaining orbital velocity.

Both choices are reasonable for what the respective companies want to
do.


They're reasonable if they work. SpaceX is trying to avoid adding other
engines to the Falcon 9 first stage.


True, and the exhaust velocity of the hypergolic fuels are less. Even so, the amounts, for an efficient system, with few redundancies, it might make sense to add the same hardware to the Falcon as was added to the Dragon V2.

The stage could hover and land,
for example, if it added Super Draco engines to the first stage.


Correct.

But,
they require different fuel and oxidizer than the first stage carries.


Which isn't really a problem for a self contained system that is compact enough to fit inside the strut housing.

This would mean adding completely different tanks, plumbing, and etc.


Four self contained plug in modules attached to the landing struts would be rather simple and require no plumbing changes of the core system. It would be far less intrusive than what they're doing right now.

for those engines. Also, if Super Dracos were used, it would be
advantageous to deplete the kerosene and then vent any remaining LOX in
the tanks before landing.


Use of the ullage at higher specific impulse with no added hardware was the sweet solution that caused them to take the route they did. However, the use of Super draco engines should also be looked at.

So, any "leftover" fuel and oxidizer would be
"wasted".


Its best to use it, especially if you're dragging along hypergolic system. Yet that system is far less weighty than wings, wheels or parachutes. Which is what I've maintained all along.

In my book, this would not be a good trade to make.


A standardised module that is adaptable to anyone elses space booster, would actually make a lot of sense and give them a product to sell to other space launch providers and adapt for recovery of upper stages as well.

All of that added complexity and added mass would cost money compared to
using "leftover" fuel and oxidizer and an engine that is already there
for launch.


The complexity from an operational point of view is nil. They're already building super dracos and flying them to land capsules. A self contained module plugged into the landing struts and tied to the avionics of a booster would be child's play and easily adapted to any stage. This would let the booster engines be optimised for their mission and let ALL the propellant be used as well.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

  #20  
Old April 9th 16, 08:03 PM posted to sci.space.policy,sci.physics,sci.astro,rec.arts.sf.science
[email protected]
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Posts: 1,346
Default Successful flight by Blue Origin

In sci.physics Fred J. McCall wrote:
wrote:

In sci.physics Fred J. McCall wrote:
wrote:

In sci.physics Fred J. McCall wrote:
Rick Jones wrote:

In sci.space.policy Jeff Findley wrote:
They're reasonable if they work. SpaceX is trying to avoid adding
other engines to the Falcon 9 first stage. The stage could hover
and land, for example, if it added Super Draco engines to the first
stage. But, they require different fuel and oxidizer than the first
stage carries. This would mean adding completely different tanks,
plumbing, and etc. for those engines. Also, if Super Dracos were
used, it would be advantageous to deplete the kerosene and then vent
any remaining LOX in the tanks before landing. So, any "leftover"
fuel and oxidizer would be "wasted". In my book, this would not be
a good trade to make.

If one wanted to give the Falcon 9 first stage the ability to hover,
wouldn't the most straightforward way to do that be create a
deeply-throttled Merlin?


Straightforward, perhaps, but it's a very big design change so you
start with having to requalify as if it's a whole new engine.

Yet you were just saying in another thread space stuff doesn't have
bureaucrat bull****.


Cite?


Sure, it was by someone called Fred J. McCall talking about nuclear
reactors on Mars being cheap for lack of bureaucrat bull****.


Wow, you REALLY don't comprehend English, do you? Either that or
you're just so intellectually dishonest everything sounds different to
you. Note that even if you interpret that one instance the way you do
(which is twisted) it doesn't say what you claim I've said.

Stop making up lies, Chimp.


Stop taking mind altering drugs, space cadet.


--
Jim Pennino
 




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