NASASpaceFlight.com Forum
General Discussion => Q&A Section => Topic started by: Zaum on 01/31/2016 05:49 pm
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Is any interplanetary probe (or other payload that needs an escape trajectory) set to be flown on a Falcon 9?
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Is any interplanetary probe (or other payload that needs an escape trajectory) set to be flown on a Falcon 9?
No but one flew already DSCOVR - it needed to get to the Earth Sun L1 and that is as close to escape velocity as makes no real difference the same sized probe could have been thrown into a heliocentric orbit.
Oh and Musk, answering question at the hyperloop event at TAMU yesterday said the current F9 could put between 3 and 4t on a trajectory to Mars.
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Indeed. The upper stage that launched DSCOVR is in heliocentric orbit, in fact.
I knew it has a pretty good capability (advertised in the User manual too), I was more wondering if there were plans on part of NASA or other space agencies to put it to use any time soon, with its low cost.
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Indeed. The upper stage that launched DSCOVR is in heliocentric orbit, in fact.
I knew it has a pretty good capability (advertised in the User manual too), I was more wondering if there were plans on part of NASA or other space agencies to put it to use any time soon, with its low cost.
Just look at the manifest or NASA's ELV manifest and you will see that there are none.
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Does SpaceX have anything to solve the problem when the Falcon 9 has to carry extra payloads in to orbit? I know they will soon be building the Falcon Heavy. I find it surprising that since the payload was heavy than usual payloads and SpaceX knew about it, that they did not add extra fuel (only if the Falcon engines has enough thruster) or may be a booster stage or use more than 3 engines? Still an impressive achievement.
Has SpaceX thought of using flaps on the Falcon 9 to slow the first stage down? Since it is mentioned that the Falcon 9 1.2v was moving faster than usual. Why has SpaceX not added nets to the barge to catch the first stage in case it lands or close to landing but tilts overs like it has done before? May save them money and reduce the clean up.
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Nets on the barge would only cause more problems.
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Has SpaceX thought of using flaps on the Falcon 9 to slow the first stage down?
Undoubtedly, yes. And what they decided to use is propulsive speed retardation, while using grid fins for aerodynamic control. See:
http://www.spacex.com/falcon9
Why has SpaceX not added nets to the barge to catch the first stage in case it lands or close to landing but tilts overs like it has done before? May save them money and reduce the clean up.
Expanding on what Jim said, among other things the Falcon 9 structure would have to be reinforced to survive being caught by nets. That would reduce overall payload.
Instead they have chosen to perfect landing upright - which they have already demonstrated successfully.
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What are the plans for transporting the landed first stage of the Falcon9 back from the sea platform? Aerial transport, or by ship? Do we know, how much it will cost about?
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Elon Musk answered this yesterday during the press conference, and it was in line with earlier announcements: the stage will remain upright on the drone ship, but will be welded to the deck. It will then go to Port Canaveral. At the port a large crane will lift the stage and put it on the shore. On the shore the same thing will happen as happened to the stage landed at LZ-1 in december: a stand will be attached to the octaweb (the base of the stage), then the legs will be folded up or taken off, and then the stage will be put horizontally on some kind of truck.
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Thanks for the quick answer! Transported on the platform itself was one of my tips, as I thought about.
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I'm trying to understand SpaceX's pricing page at http://www.spacex.com/about/capabilities
1) There seem to be two different amounts of payload listed to GTO for F9: 5.5 mT and 8,300 kg. What's the difference between the two?
2) Are the $62M hardware and logistics?
2a) If so, then by comparing F9 and FH prices, would it be correct to assume the cost for one F9 S1 to be about $14M including fuel?
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I'm trying to understand SpaceX's pricing page at http://www.spacex.com/about/capabilities
1) There seem to be two different amounts of payload listed to GTO for F9: 5.5 mT and 8,300 kg. What's the difference between the two?
2) Are the $62M hardware and logistics?
2a) If so, then by comparing F9 and FH prices, would it be correct to assume the cost for one F9 S1 to be about $14M including fuel?
1) $62M buys you 5500 kg to GTO. If you want more, you'll have to pay more, up to a maximum of 8300. Presumably 5500 kg is the limit where recovery is possible, expending the whole rocket will be more expensive in the future.
2) As I understand it this is the price for the launch service, with everything the standard option and no extra options such as spin-stabilisation.
2a) The stage may cost about that much, but maybe integration and launch costs are higher for Falcon Heavy because it consists of more stages.
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Not a complicated question.
During the launch preparation, what is LOX drainback?
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Not a complicated question.
During the launch preparation, what is LOX drainback?
Here's a description for STS. Once LOX loading is complete, the fill and drain valve or valves in the rocket close(s) (there is probably one for each stage). LOX in the lines then drains back to the ground support equipment. For STS, a second "outboard" fill and drain valve closed after the drain back was complete.
https://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/prop/flowsequence.html
- Ed Kyle
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More on grid fins. A little-appreciated fact is that the rocket must generate aerodynamic lift during at least part of its climb to orbit. Rather than do this by adding an angle of attack to the whole stack, would it make sense to launch with the grid fins deployed (presumably permanently) and use their lifting ability for that purpose? Using them might result in a lower lift/drag ratio than using the entire rocket body, and would eliminate some weight, complexity and a point of failure in the deployment mechanism. There might also be an opportunity to reduce or even eliminate the gimbal authority required on some of the main engines.
On the downside, it would certainly concentrate lifting stress at the fin location on the tube, rather than distributing it along the length of the tube. And it would do nothing for the second stage, since the fins would remain with the first stage when it separates, as they do now.
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And I should have added that the deployed grid fins could contribute to yaw and roll control, in addition to pitch (lift), further reducing engine gimbal authority required.
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A little-appreciated fact is that the rocket must generate aerodynamic lift during at least part of its climb to orbit.
Say what?
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...would it make sense to launch with the grid fins deployed (presumably permanently) and use their lifting ability for that purpose?
No. Grid fins don't produce lift, they produce drag.
Using them might result in a lower lift/drag ratio than using the entire rocket body...
They are too small to affect the full mass of a launching rocket (i.e. most of the fuel & still carrying the 2nd stage), and the current design wouldn't be able to push the grid fins out into the air stream in any case.
SpaceX has shown to be full of a lot of smart engineers, and if this was something that was useful they would have tried it.
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https://www.youtube.com/watch?v=o0Yc81t732k
Note where he discusses that the grid fins at the rear of the MOAB move the center of pressure back and that enables controllability. Now move those grid fins forward, moving the CP ahead of the CG and see what happens to your rocket.
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A. Grid fins produce both lift and drag just like any wing. They are merely a novel configuration of a wing that packages a lot of lift area in a dimensionally small structure that is more suited to use at very high speeds than a single high-aspect wing of equal area.
B. There is nothing inherently improper with wings or fins located forward on the body of a missile, as they are on virtually every air-to-air missile in existence. The fact that they are located on the aft end of the MOAB is a design choice appropriate to their application in a minimalistic guidance system of a gravity bomb.
C. The concept was not that the grid fins would be extended against the slipstream, but that they would be fixed in the extended position and their angle of attack varied... sort of like a wing.
D. I am not convinced that Spacex engineers should be assumed to have considered all conceivable solutions. While I am sure they are exceptionally clever, so too were their Apollo predecessors, for example, who would have howled at the thought of boosters returning to the launch site and landing tail-first... an idea nearly as preposterous as putting control surfaces toward the front of a rocket.
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I believe that Elon Musk mentioned the angle of attack required of the rocket body cylinder during the press conference after the most recent launch.
Rockets that are going to orbit cannot follow a purely ballistic trajectory like an artillery rocket intended to come back down to impact the ground. Prior to obtaining orbital velocity, an orbit-bound rocket must maintain a slight "nose high" attitude to develop a thrust vector upward, preventing it from descending below the desired trajectory, unless it has wings!
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A little-appreciated fact is that the rocket must generate aerodynamic lift
Not true at all.
https://www.youtube.com/watch?v=n4yYZh1U908
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I believe that Elon Musk mentioned the angle of attack required of the rocket body cylinder during the press conference after the most recent launch.
It is not "required" but minimized
B. There is nothing inherently improper with wings or fins located forward on the body of a missile, as they are on virtually every air-to-air missile in existence. The fact that they are located on the aft end of the MOAB is a design choice appropriate to their application in a minimalistic guidance system of a gravity bomb.
Look at your words: missile, air to air, etc. Launch vehicles are not missiles, especially ones that operate at less than 50kft.
Launch vehicles spend most of the time out of the atmosphere.
Prior to obtaining orbital velocity, an orbit-bound rocket must maintain a slight "nose high" attitude to develop a thrust vector upward, preventing it from descending below the desired trajectory, unless it has wings!
Wrong. Launch vehicles don't flight with "canted" thrust vector to counter gravity. The rocket is in free flight, there is no side gravity force. An astronaut only feels the thrust of the engine and not a pull to the center of the earth and not to a floor like an airplane. If an airplane had strong enough engines, it wouldn't need wings.
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I believe that Elon Musk mentioned the angle of attack required of the rocket body cylinder during the press conference after the most recent launch.
That angle of attack and aerodinamic lift from the rocket body cylinder were for minimizing the boostback fuel in RTLS manouvers, not to help in the ascending phase.
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Launch vehicles spend most of the time out of the atmosphere.
Prior to obtaining orbital velocity, an orbit-bound rocket must maintain a slight "nose high" attitude to develop a thrust vector upward, preventing it from descending below the desired trajectory, unless it has wings!
Wrong. Launch vehicles don't flight with "canted" thrust vector to counter gravity. The rocket is in free flight, there is no side gravity force. An astronaut only feels the thrust of the engine and not a pull to the center of the earth and not to a floor like an airplane. If an airplane had strong enough engines, it wouldn't need wings.
Launch vehicles are absolutely under the pull of gravity - they must either fly with some component of the thrust vector countering gravity, or they must accelerate under gravity. What they don't do is counter gravity with aerodynamic lift, because (as Jim noted) there is no atmosphere for most of the vehicle's flight.
The idea that rockets need aerodynamic lift for anything is totally misguided. It's trivial to have a thrust component that is countering gravity but is not "canted" relative to the vehicle or its direction of travel - you simply point the rocket varying amounts of "up" while always thrusting and traveling in the direction the rocket is pointed (i.e. angle of attack is always zero).
Any thrust component that is opposing gravity is not accelerating the vehicle downrange, and so is contributing to gravity losses. At liftoff the rocket is entirely vertical, so a large fraction of the booster's thrust is countering gravity, with the rest accelerating the vehicle upward. So most gravity losses are incurred near liftoff.
To reduce gravity losses (or more precisely, to absorb them primarily with the heavy booster(s) and not a light upper stage) many vehicles loft the upper stage far outside the atmosphere, where it slows vertically and eventually starts falling back without attempting to thrust to counter gravity. But as it slows vertically, it is accelerating downrange so to reach orbital velocity before falling back into the atmosphere. Orbit, of course, is a free-fall that never reaches the ground.
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Forgive me if this is covered elsewhere, couldn't find anything.
I've just noticed that the SpaceX coverage of NROL-76 uses m/s (metres per second), but CRS-13 uses km/h (unit of the antichrist).
The former is a proper SI unit of speed (yes I know some of you want feet per second or furlongs per fortnight, but SpaceX went metric, don't blame me).
My problem is km/h. Really? The only time I have ever seen that is the speedometer in a car.
Ok, so I'm British and less than 60 so I use m/s for engineering. When I'm driving, it's miles/hr.
I would be willing to bet SpaceX use SI units (kg/seconds/metres) internally. So why on earth would they switch the coverage to use km/h?
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Forgive me if this is covered elsewhere, couldn't find anything.
I've just noticed that the SpaceX coverage of NROL-76 uses m/s (metres per second), but CRS-13 uses km/h (unit of the antichrist).
The former is a proper SI unit of speed (yes I know some of you want feet per second or furlongs per fortnight, but SpaceX went metric, don't blame me).
My problem is km/h. Really? The only time I have ever seen that is the speedometer in a car.
Ok, so I'm British and less than 60 so I use m/s for engineering. When I'm driving, it's miles/hr.
I would be willing to bet SpaceX use SI units (kg/seconds/metres) internally. So why on earth would they switch the coverage to use km/h?
Km/h are what 90% of the world uses (http://chartsbin.com/view/5261) for measuring speed, and is only used on the hosted webcast targeted at a general audience.
The technical webcast (when it's broadcast, which is not every flight) only shows m/s.
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They're either Canadian (or Mexican) or trolling all the KSP players out there.
PS I'd vote for m/s if I had a vote
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So all I'm seeing is a difference between the technical and hosted (non-technical) webcasts? I've watched many (all?) of both, never realized.
I do not get on with km/h (as you may have guessed). For some reason I have trouble converting that in my head to m/s, whereas feet per second, miles per hour are no problem.
Sigh. Another conversion constant to try to remember...
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The technical webcast (when it's broadcast, which is not every flight) only shows m/s.
Well, not really. Not consistently, anyway. The CRS-13 technical webcast showed km/h.
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For some reason I have trouble converting that [km/h] in my head to m/s,
Divide by 4, then add 10% of your new total. quick conversion. It's obviously not perfectly accurate. But the actual conversion is to multiply by (1000/3600)=0.277| (sorry that's supposed to be 7s repeating, not sure how to type a bar) and my way is the same as multiplying by 0.275. If you need additional accuracy, you can keep taking and adding 10% of your previous 10%. So, say the speed is 8000 km/h. That gives 2000 +200 +20 +2 +..... and just keep adding 10% of the previous adjustment until you reach enough accuracy.
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One question can't seem to find the answer for. Does F9 use Draco engines as RCS or just nitrogen thrusters? Thanks.
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Nitrogen.
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My problem is km/h. Really? The only time I have ever seen that is the speedometer in a car.
I would be willing to bet SpaceX use SI units (kg/seconds/metres) internally. So why on earth would they switch the coverage to use km/h?
I would like they use km/s (or m/s, conversion is trivial). Something like 18000 km/h is absurd number. I never encountered such long distances in my life and have no slightest idea how fast 18000 km/h is.
In contrast, 5000 m/s (or 5 km/s) is the distance from my home to Auchan, covered in just one second. Wow, it's pretty fast!
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My problem is km/h. Really? The only time I have ever seen that is the speedometer in a car.
I would be willing to bet SpaceX use SI units (kg/seconds/metres) internally. So why on earth would they switch the coverage to use km/h?
I would like they use km/s (or m/s, conversion is trivial). Something like 18000 km/h is absurd number. I never encountered such long distances in my life and have no slightest idea how fast 18000 km/h is.
In contrast, 5000 m/s (or 5 km/s) is the distance from my home to Auchan, covered in just one second. Wow, it's pretty fast!
I provided a quick method of estimating a conversion from km/h to m/s in response to @nicp's original complaint. It's very easy.
http://forum.nasaspaceflight.com/index.php?topic=39481.msg1762532#msg1762532
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My problem is km/h. Really? The only time I have ever seen that is the speedometer in a car.
I would be willing to bet SpaceX use SI units (kg/seconds/metres) internally. So why on earth would they switch the coverage to use km/h?
I would like they use km/s (or m/s, conversion is trivial). Something like 18000 km/h is absurd number. I never encountered such long distances in my life and have no slightest idea how fast 18000 km/h is.
In contrast, 5000 m/s (or 5 km/s) is the distance from my home to Auchan, covered in just one second. Wow, it's pretty fast!
km/h is the perfect unit of measurement for communicating with the general public. Suggestions of using any other unit of measurement is demanding the company adopt the policy of communicating with the general public in gibberish.
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For some reason I have trouble converting that [km/h] in my head to m/s,
Divide by 4, then add 10% of your new total. quick conversion. It's obviously not perfectly accurate. But the actual conversion is to multiply by (1000/3600)=0.277| (sorry that's supposed to be 7s repeating, not sure how to type a bar) and my way is the same as multiplying by 0.275. If you need additional accuracy, you can keep taking and adding 10% of your previous 10%. So, say the speed is 8000 km/h. That gives 2000 +200 +20 +2 +..... and just keep adding 10% of the previous adjustment until you reach enough accuracy.
Actually, there's an easier way - the conversion factor is 3.6. There are 3600 seconds in an hour; a kilometer is 1000 meters. Therefore, an object travelling 1m/s travels 3.6km in an hour. So, 18000km/h = 5000m/s, because 18000 / 3.6 is 5000, while 7000m/s = (7000 * 3.6)km/h = 25,200km/h.
Easy conversions like that are one of the advantages of the metric system. :P
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For some reason I have trouble converting that [km/h] in my head to m/s,
Divide by 4, then add 10% of your new total. quick conversion. It's obviously not perfectly accurate. But the actual conversion is to multiply by (1000/3600)=0.277| (sorry that's supposed to be 7s repeating, not sure how to type a bar) and my way is the same as multiplying by 0.275. If you need additional accuracy, you can keep taking and adding 10% of your previous 10%. So, say the speed is 8000 km/h. That gives 2000 +200 +20 +2 +..... and just keep adding 10% of the previous adjustment until you reach enough accuracy.
Actually, there's an easier way - the conversion factor is 3.6. There are 3600 seconds in an hour; a kilometer is 1000 meters. Therefore, an object travelling 1m/s travels 3.6km in an hour. So, 18000km/h = 5000m/s, because 18000 / 3.6 is 5000, while 7000m/s = (7000 * 3.6)km/h = 25,200km/h.
Easy conversions like that are one of the advantages of the metric system. :P
Maybe you missed the part where nicp said, "in my head"? Sure, multiplying and dividing by 3.6 is going to get you an accurate result and is simple enough with a calculator. But the method I mentioned is much better for "in your head" math.
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What material is used for the Octaweb? It looks like a heavy piece of kit, just wondered if it was Aluminium, Aluminium alloy, Steel or even Titanium? I guess that even with 10 flights expected for the block 5's that that amount of Titanium would be too expensive?
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This is a good question. I always assumed it was titanium, but SpaceX published pictures of a worker welding (TIG?) on it in the open air, which doesn't really work with titanium. So I'd guess either Li-Al alloy or stainless steel.
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From the reddit comment (https://www.reddit.com/r/spacex/comments/60d41s/official_spacex_glassdoor_image_falcon_9_octaweb/df6aibs/) of an ex-employee who welded the octaweb:
2219 aluminum/lithium alloy
This is from a year ago, but I doubt they'll change it for Block 5.
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Somewhere along the way(Block 4ish?) they changed to an octaweb that's bolted instead of welded.
So the material might have changed.
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From Elon's Block 5 phone presser transcript:
But this is a much stronger octaweb structure. It's made of a much higher strength of bolted aluminum. A 7000 series instead of a 2000 series.
So they did change it for block 5.
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Used to be welded together, now it's bolted which (according to Space X) makes building and refurb easier.
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Is it known which core F9R Dev2 is/was? I thought I read somewhere that it was core 1007, but I couldn't find any of this info again.
Thanks for the help!
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What are those short towers around the launch pad of Falcon 9 used for?
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Lightning protection.
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Leftovers from Titan IV
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Plus, they're not exactly short. They're what, 250 feet tall just to the bottom of that white cylinder, which is another 150 ft high?
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https://www.google.com/search?q=cape+canaveral+lightning+protection&tbm=isch
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Why not just a metal spike at the top? What's with the white cylinder bits?
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Because the towers themselves are not meant to be isolated ligthning rods. If you look carefully at SLC-40 imagery, you'll see catenary wires going between all four towers and a middle grid inside that one. The purpose of the towers is to create a "net" by shielding the launch vehicle from high electric field tension when a lightning strike hits, sort of like a Faraday cage does. It's not supposed to *attract* lightning.
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What's with the white cylinder bits?
"The big top rods are insulators ... spun fiber in polymer matrix structure ... at the time the biggest such cylinder in the world."
"The fiberglass (FRP) tubes on the top of the launch platforms are a part of a lightning protection system and are insulators with cables that form a cone of protection for the launch tower. They were designed by my former company CH2M HILL, (Gainesville,FL)an engineering firm, and were manufactured by Starline Fabricators, Astatula, FL"
https://space.stackexchange.com/questions/2958/what-are-the-towers-around-the-spacex-launch-pad-used-for
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thx - does that mean that Starship will need an even bigger set up? Or will that be different because its made of Stainless?
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Do we know how much thrust the RCS of the first stage of the falcon 9 produce?
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Ariane 5 just launched 3 satellites to GTO. How many launches would it take the falcon 9 to launch them?
two
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Amazing photos. Seems so surreal it can light engines on the way back when the forces must be pushing some plume back on to the engines themselves. Sorry for the newbie question, but how do they protect the bottom of the Falcon 9 from that?
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Amazing photos. Seems so surreal it can light engines on the way back when the forces must be pushing some plume back on to the engines themselves. Sorry for the newbie question, but how do they protect the bottom of the Falcon 9 from that?
The bottom of Falcon9 has a heat-shield for that reason. I's design changed a couple of times over F9's design iterations. The rigid parts are easy, they are simply coated in a sufficiently heat resistant material. But the engines gimbal and that makes it necessary that parts of this shield are flexible. In the past SpaceX used something that looked like asbestos cloth you find in furnace-mits and similar, but these have shown holes and other signs of burn through after booster-recovery. The block5 iteration has something better, but the exact design is probably a trade secret ;)
Nevertheless SpaceX has encountered heatshield failures on some extreme reentry recovery attempts. (B1057 - Falcon Heavy Center Core suffered from TVC failure on center engine after a heat shield burn-through -> aborted landing)
The nozzles themselfes don't need protection, they are designed to cope with rocket exhaust and have active cooling channels in their walls.
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I think Shotwell was quoting Musk though when she said [Re: Elon Musk criticized Grasshopper's test campaign as having been "not aggressive enough" as the test article ended up surviving all tests.]. I don't have the exact source/video, though.
Link/Reference anyone? It should be public, but I don't know where to look.
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I'm puzzled why Falcon 9 throttles down through Max Q. I can understand why Falcon 9 Heavy (as well as Shuttle, Delta IV Heavy, etc.) does this to reduce aerodynamic loads on the booster attach points. But F9 is single stick. My best guess is that the vehicle velocity approaching Max Q dictates the need for throttle down. Or this is required by Dragon, not the booster? Or if Space X built Dragon and Falcon 'beefy' enough to endure full Max Q, there would be a weight penalties.
Sidebar coments:
- I just watched the last Delta IV Medium (two SRBs) launch. Didn't hear an RS-68A throttle down comment.
- I think the Shuttle was first vehicle to utilize throtte down simply because it had the first throttleable engines.
- The original Atlas rocket is an interesting case. It was famous (or infamous!) for it's thin-skin construction. As far as I know it survived Max Q every time with its fixed-thrust engines.
Thanks
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I'm puzzled why Falcon 9 throttles down through Max Q. I can understand why Falcon 9 Heavy (as well as Shuttle, Delta IV Heavy, etc.) does this to reduce aerodynamic loads on the booster attach points. But F9 is single stick. My best guess is that the vehicle velocity approaching Max Q dictates the need for throttle down. Or this is required by Dragon, not the booster? Or if Space X built Dragon and Falcon 'beefy' enough to endure full Max Q, there would be a weight penalties.
Sidebar coments:
- I just watched the last Delta IV Medium (two SRBs) launch. Didn't hear an RS-68A throttle down comment.
- I think the Shuttle was first vehicle to utilize throtte down simply because it had the first throttleable engines.
- The original Atlas rocket is an interesting case. It was famous (or infamous!) for it's thin-skin construction. As far as I know it survived Max Q every time with its fixed-thrust engines.
Thanks
Delta IV and Atlas V (and so will Vulcan) also throttle down. It has nothing to do with "booster attach points", but rather loads on the vehicle and payload. The shuttle had an additional reason because of the aerosurfaces. Throttling down prevents the vehicle from accelerating too fast through the lower atmosphere and keeps max q to less than 1000 psf (I think around 700, the same as the Saturn V). Throttling also reduces the max g which is usually just before core burnout.
Classic Atlas and Saturn V had lower T/W and accelerated slower through the lower atmosphere.
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Thanks Jim. Your breath and depth of knowledge is worth umteen times my NSF subscription price.
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keeps max q to less than 1000 psf (I think around 700, the same as the Saturn V).
The 700 lbs/ft2 Max Q came later for shuttle. It was a Performance Enhancement. Earlier was around 670/ft2.
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Why does the SpaceX Launch Director give his GO for every Falcon launch at T-45 seconds? Shouldn’t it be earlier in the count?
Also, I noticed before the Falcon Heavy Test Flight, the Launch Director gave his GO at T-25 seconds. That’s cutting it close, right?
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Why does the SpaceX Launch Director give his GO for every Falcon launch at T-45 seconds? Shouldn’t it be earlier in the count?
Also, I noticed before the Falcon Heavy Test Flight, the Launch Director gave his GO at T-25 seconds. That’s cutting it close, right?
The range gives him a go late in the count. As long as there is a place to safely stop the count, it isn't too late.
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Hi,
is there any paper/video on YouTube/anywhere else describing what happens if you rotate one/two/all grid fins on Falcon 9 booster? Any video/paper about control authority? I'm just wondering what would have happened if you rotated for example two opposite fins, etc.
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With the recent weather scrubs of Falcon it got me wondering, is there a limit on how many tankings it can do?
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With the recent weather scrubs of Falcon it got me wondering, is there a limit on how many tankings it can do?
Since Elon has said there are no obvious limits to Falcon 9 reuse, then tankings should be included.
The number is high, but not infinite. My guesstimate is about 100?
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With the recent weather scrubs of Falcon it got me wondering, is there a limit on how many tankings it can do?
Since Elon has said there are no obvious limits to Falcon 9 reuse, then tankings should be included.
The number is high, but not infinite. My guesstimate is about 100?
I can see the design limits to be above 100 tankings. On the other hand, I can see a much lower number (10?) for the number of times SpaceX would fill the Falcon 9 with propellants and detank before pulling the rocket down to conduct some inspections.
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It appears the external cameras on the first stage have some method of clearing the view after entry burn fouling. I can think of a few ways this might be accomplished, but not sure what is used. Rotating shield that moves to a clean spot? That would require a servo or similar which seems odd to me. Is there a reference for how this is done?
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It appears the external cameras on the first stage have some method of clearing the view after entry burn fouling. I can think of a few ways this might be accomplished, but not sure what is used. Rotating shield that moves to a clean spot? That would require a servo or similar which seems odd to me. Is there a reference for how this is done?
No cleaning methods other than the supersonic airflow blasting the camera fairing window that can impinge once the burn ends.
The 'wipe' is shadowing and internal glare from the vehicle moving relative to the sun. The effect of the airflow is most visible for RTLS landings (as the trajectory is more vertical the the time between end of the entry burn and hitting the denser lower atmosphere at speed is much shorter than for the shallower downrange landings) and more dramatic for Falcon Heavy due to the heavy fouling from the separation and boostback (the deposits are visible long before the entry burn starts).
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Does SpaceX ever put previously flown engines on unflown expendable cores?
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Does SpaceX ever put previously flown engines on unflown expendable cores?
I presume you are really asking if SpaceX puts older engines they are willing to lose onto new, expended Falcon Heavy cores. There is no way to know this outside of someone at SpaceX explicitly saying they installed older, previously flown engines on an expended core.
However, SpaceX does engine swaps all the time, and there is no particular reason why a previously flown engine could not be installed on a new booster. The Merlin engines are effectively interchangeable and can be installed on any first stage.
Unless the customer specifies that they want completely new engines to fly on their booster, SpaceX can assign engines to that launch as they please.
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Why does NASA Launch Services Program's Launch Vehicle Performance Website (https://elvperf.ksc.nasa.gov/) not show Falcon performance for many orbits? For example the orbits (i) 200 km 28.5 degree LEO and (ii) C3 = -2 km^2 / s^2 high energy show performance numbers for other launchers but not for Falcon 9 or Falcon Heavy.
Edit: Falcon 9 and Falcon Heavy do show up for some orbits, e.g. C3 = -1.5 km^2 / s^2.
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What is the use of a entry burn for RTLS, especially FH boosters?
The RTLS entry burn start speed (4000km/hr) is less than the ASDS (barge) landing entry burn end speed (~6000km/hr).
Info I've gathered from webcast telemetry.
RTLS One Web 16 Jan 9 2023
Payload mass kg 5900 40x 147.5 = 5900 plus dispenser (1000kg??)
Entry Burn start speed 4473
Entry Burn end speed 2926
FH side booster RTLS USSF-67 Jan 2023
Payload mass kg ??? to GEO
Entry Burn start speed 4472
Entry Burn end speed 3690
F9 RTLS ISI EROS C-3 Dec 29 2022 Vandenburg
Payload mass kg 470
Entry Burn start speed 4651
Entry Burn end speed 2616
F9 ASDS Starlink Dec 17th 2022 Cape
Payload mass kg
Entry Burn start speed 8152
Entry Burn end speed 6074
Distance to ASDS km est 656
F9 ASDS Starlink 5-1 Dec 28th 2022 Cape
Payload mass kg 16200 54x300kg Starlink 1.5
Entry Burn start speed 8026
Entry Burn end speed 5627
Distance to ASDS km 660
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What is the use of a entry burn for RTLS, especially FH boosters?
The RTLS entry burn start speed (4000km/hr) is less than the ASDS (barge) landing entry burn end speed (~6000km/hr).
Info I've gathered from webcast telemetry.
RTLS One Web 16 Jan 9 2023
Payload mass kg 5900 40x 147.5 = 5900 plus dispenser (1000kg??)
Entry Burn start speed 4473
Entry Burn end speed 2926
FH side booster RTLS USSF-67 Jan 2023
Payload mass kg ??? to GEO
Entry Burn start speed 4472
Entry Burn end speed 3690
F9 RTLS ISI EROS C-3 Dec 29 2022 Vandenburg
Payload mass kg 470
Entry Burn start speed 4651
Entry Burn end speed 2616
F9 ASDS Starlink Dec 17th 2022 Cape
Payload mass kg
Entry Burn start speed 8152
Entry Burn end speed 6074
Distance to ASDS km est 656
F9 ASDS Starlink 5-1 Dec 28th 2022 Cape
Payload mass kg 16200 54x300kg Starlink 1.5
Entry Burn start speed 8026
Entry Burn end speed 5627
Distance to ASDS km 660
Entry burns are to reduce velocity and therefore aerodynamic heating of the booster during re-entry. This is needed whether the booster is heading for a drone ship landing or an RTLS landing. The altitude and duration of the entry burn is carefully calculated to use the least possible amount of fuel while keeping the heating of the rocket below the safe limit.
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The previous answer deftly avoided the question.
WHY does Spaces even bother with a RTLS entry burn since the ENDING velocity of an ASDS is greater than the START velocity of an RTLS entry burn.
The altitude and duration of the entry burn is carefully calculated to use the least possible amount of fuel while keeping the heating of the rocket below the safe limit.
This doesn't hold water since the entry burn time is identical and altitude is very close between RTLS and ASDS.
Entry Burn start Entry burn end Entry burn time Altitude at End of Entry burn
km/hr km/hr seconds km
F9 RTLS One Web 16 Jan 9 2023 4473 2926 19 32.4
FH side booster RTLS USSF-67 Jan 2023 4472 3690 21 34.5
F9 RTLS ISI EROS C-3 Dec 29 2022 Vandy 4551 2616 21 31
Average RTLS 4499 3077 20 33
F9 ASDS Starlink Dec 17th 2022 Cape 8155 6074 18 36.1
F9 ASDS Starlink 5-1 Dec 28th 2022 Cape 8026 5627 23 41.6
F9 ASDS Starlink January 19 Vandy 8110 5843 19 35.8
Average ASDS 8097 5848 20 38
Difference 3598 2771 0 5
Entry burn starts range from 6:07 to 6:51 with RTLS starts tending to be a little earlier.
Speculation on reasons for this, in the hopes of invoking Cunningham's Law https://en.wiktionary.org/wiki/Cunningham%27s_Law
Commonality of Operations?
Doesn't make sense, SpaceX seems to have a pretty darn good grasp on writing real-time adaptive control software.
Vehicle control ?
But the same question applies to the relative ENDING velocity.
RTLS is probably more nearly vertical than ASDS?
Perhaps just making the later entry less stressfull for RTLS, as in you might be able to have lesser structural and heating loads.
Reducing cold-gas RCS thruster requirements?
An on a non-sequitor note: Does anybody have suggestions for a good way to insert spreasheet tables that you don't have to hand-tweek? A PM and or a pointer to an answering thread would be appreciated.