Author Topic: Could a Falcon 9R fly to 100km altitude and land back?  (Read 21214 times)

Online Ben the Space Brit

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #80 on: 12/22/2015 11:10 AM »
I still like the idea of putting a modified Crewed Dragon on top of an F9R and using it for suborbital tourist rides.
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Offline CraigLieb

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #81 on: 12/22/2015 06:38 PM »
Tangential question (requesting general speculation based on the last launch parameters): 
If after the 1st stage was done with its primary task, what if it used all its remaining fuel to boost to orbital velocity rather than return stage burns, landing burns, etc. Would it have been able to orbit at least once before reentry?
Given: somewhat empty stage 1, at altitude greater than 100 km, already at 5000 km/sec. what kind of delta v boost would it need to do a 100 km orbit?  Was the launch profile too lofted for that kind of thing?  Air resistance still too high at that altitude?

Any takers of the challenge?
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Online hkultala

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #82 on: 12/22/2015 06:46 PM »
Tangential question (requesting general speculation based on the last launch parameters): 
If after the 1st stage was done with its primary task, what if it used all its remaining fuel to boost to orbital velocity rather than return stage burns, landing burns, etc. Would it have been able to orbit at least once before reentry?
Given: somewhat empty stage 1, at altitude greater than 100 km, already at 5000 km/sec.

5000km/sec speed is not close to orbital speed. It's much higher speed than escape speed from the solar system.

And Falcon 9 first stage cannot reach it.


The speed at staging was about 5900 km/h which means ~1640 m/s.

This is about 6km/s short of orbital velocity, so at least 6km/s delta-v is needed to get from that to orbit.
And 6km/s is way too much.  And there would be no point of having second stage on LEO launches if first stage would anyway reach orbital velocity.
« Last Edit: 12/22/2015 06:53 PM by hkultala »

Offline Lars-J

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #83 on: 12/22/2015 06:48 PM »
Tangential question (requesting general speculation based on the last launch parameters): 
If after the 1st stage was done with its primary task, what if it used all its remaining fuel to boost to orbital velocity rather than return stage burns, landing burns, etc. Would it have been able to orbit at least once before reentry?

It would not be enough. Musk has mentioned that the stage 1 one could probably reach orbit on its own - with no upper stage or payload - although it would not be able to come back.

Given this information, it is pretty clear that after dropping off the 2nd stage and payload, it would have fallen far short of reaching orbit if it tried. Remember that the first stage in this mission only provided ~1/4th of the delta V needed for orbit.
« Last Edit: 12/22/2015 06:50 PM by Lars-J »

Offline Bob Shaw

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #84 on: 12/22/2015 07:14 PM »

Heck yea it did! Does the Apollo Lunar Module get any recognition for a vertical landing vertical takeoff? Or does it have to be in the proper order ;)

In that case, I bid Surveyor 5.

Offline JasonAW3

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #85 on: 12/22/2015 07:40 PM »
Amusing thought here;

     If the BFR winds up being capible of getting itself and a small payload into orbit with a single stage, I wonder how hard it would be to go, "Dry for Wet" with the stage and convert it into a "Super Skylab?

     Doing it with a Falcon 9 maybe possible, but I'm not sure the volume constraings would make the effort worth the cost.
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Offline QuantumG

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #86 on: 12/22/2015 10:53 PM »
It would not be enough. Musk has mentioned that the stage 1 one could probably reach orbit on its own - with no upper stage or payload - although it would not be able to come back.

By my math it'd do about 9500 m/s and still have whatever is usually required for a drone ship return. If your goal is to do a "single orbit" flight, that's excessive. You could do a bigger "boost back" burn to slow down for entry interface. If you put a heat shield inside a faring on top of the first stage, drop off the faring on ascent and use the heat shield to slow down for reentry, that should do it. Not that there'd be much point.

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Offline inventodoc

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #87 on: 12/22/2015 11:05 PM »
Amusing thought here;

     If the BFR winds up being capible of getting itself and a small payload into orbit with a single stage, I wonder how hard it would be to go, "Dry for Wet" with the stage and convert it into a "Super Skylab?

     Doing it with a Falcon 9 maybe possible, but I'm not sure the volume constraings would make the effort worth the cost.

Either a nice big dry space or Wet to Dry is the way to go!  I'd love to see Skylab and original Von Braun vision space stations. 

Offline Dante80

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #88 on: 12/27/2015 06:44 AM »
It would not be enough. Musk has mentioned that the stage 1 one could probably reach orbit on its own - with no upper stage or payload - although it would not be able to come back.

By my math it'd do about 9500 m/s and still have whatever is usually required for a drone ship return. If your goal is to do a "single orbit" flight, that's excessive. You could do a bigger "boost back" burn to slow down for entry interface. If you put a heat shield inside a faring on top of the first stage, drop off the faring on ascent and use the heat shield to slow down for reentry, that should do it. Not that there'd be much point.

The discussion is purely theoretical of course, but it would not be easy for that to work. Most on the mass is on the engine side, and the stage is 48m long. This means that trying to balance re-entry on the other side (interstage heat shield) would be very, very hard.
« Last Edit: 12/27/2015 06:45 AM by Dante80 »

Offline QuantumG

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #89 on: 12/28/2015 12:08 AM »
The discussion is purely theoretical of course, but it would not be easy for that to work. Most on the mass is on the engine side, and the stage is 48m long. This means that trying to balance re-entry on the other side (interstage heat shield) would be very, very hard.

Yep, it's called a "death swoop" and it generally requires a powered reentry.
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Offline Rik ISS-fan

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #90 on: 01/02/2016 04:09 PM »
The original question has been ansered. Could Falcon 9R fly to 100km altitude and land back. YES, Falcon 9R staged at 80km, with a speed of 5,? Km/h (roughly mach5). It restarted 3engines to return to the landing pad and reached a apogee of over 200km before it landed after two one engine burns. (Right?)
Lets change the question in: How does Falcon 9R compare to the Darpa XS-1 requirements?
With changes are required to reach the xs-1 requirements?

The requirements for Darpa XS-1 are:
- It should reach mach10,
- cost less than 5mln to launch.
- can launch 10 times in 10 days.
- with an expendable upper-stage a payload with a mass between 3000-5000 pounds can be launched

My impression is that F9R can launch more than 25 000 pounds for about 10mln. And can relaunch within 48 hours (so 5 launches in 10 days). But it stages at about half the speed so F9R relies much more on the upperstage. I think with 5 merlin 1d trust level lox-lch4 engines the darpa xs-1 requirement of 3000-5000 pounds and 10 launches within 10 days could be reached. I'm not sure if a higher speed att staging is a better approach than what spacex has chosen for F9R. please comment how you think about this and if you have beter data about F9R to compare it with the requirements.
« Last Edit: 01/02/2016 04:21 PM by Rik ISS-fan »

Offline deltaV

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Re: Could a Falcon 9R fly to 100km altitude and land back?
« Reply #91 on: 01/02/2016 11:25 PM »
The requirements for Darpa XS-1 are:
- It should reach mach10,
- cost less than 5mln to launch. [Emphasis added by deltaV]
- can launch 10 times in 10 days.
- with an expendable upper-stage a payload with a mass between 3000-5000 pounds can be launched
Those cost and launch tempo requirements are roughly 10 times better than what Falcon can do currently. Maybe they'll get there eventually, but not in time for the XS-1 program I'm guessing.

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