Author Topic: SpaceX FH : Falcon Heavy Demo : Feb 6, 2018 : Discussion Thread 2  (Read 598050 times)

Offline MaxTeranous

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A question that just occurred to me: I think that we're all in agreement that the initial orbit of the Tesla Roadster will take it nowhere near Mars due to a difference in alignment. Is there any likelihood of precession or orbital mechanics bringing the Roadster to Mars in less than 100 years?

I think the expectation is that it'll also be targeted so that apogee is well above the orbital plane, so that even if Mars would be impacted in a 2D plane, it's not in the 3D.

Given enough time ofc nothing is certain about any orbit.

Offline Ronpur50

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I hoped I am mistaken but it seems the line of sight to 2 incoming boosters may ended a a mile above LZ-1 from Apollo/Saturn Center area since the VAB (500' high) is blocking and is ten times closer than LZ-1?

I was at the Dragon 13 launch in December, and from the point of view of the Banana River Stands, the booster landed just in front of the VAB.  You can see it.  I was in the side closest to the VAB as well.
« Last Edit: 01/30/2018 02:31 pm by Ronpur50 »

Offline .Scott

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To reduce the perigee from Earth to Venus, the minimum delta-V solution would require a retrograde burn at apogee, ie more energy.
Not true.  If your delta V was either directly towards the sun or away from it, the resulting heliocentric orbits would be very similar.  In both cases a single burn would result in an orbit with higher than Earth apogee and a lower than Earth perigee.

Offline Pete

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A question that just occurred to me: I think that we're all in agreement that the initial orbit of the Tesla Roadster will take it nowhere near Mars due to a difference in alignment. Is there any likelihood of precession or orbital mechanics bringing the Roadster to Mars in less than 100 years?

Nope, as the Tesla's orbital plane will not match Mars' orbital plane.
(it *cannot* do so for a launch now, without also needing a mid-course plane changing maneuver)
.
.
So to meet Mars it would not only need to happen to be at the right distance from the sun, it would *also* need to do so at one of the two times per Mars orbit when the planet is also at the intersection of the planes. Except that these two events cannot possibly happen at the same time, as the Tesla will be on an orbit between Earth and Mars orbits that crosses Mars' orbital plane while the Tesla is less than halfway out on its orbit.
.
The only way to get Tesla and Mars to ever meet, would be for the Tesla's orbit to first meet Earth, and get *just exactly* the gravity sling to change its orbital plane to match Mars.
Not impossible, but winning 3 consecutive Powerball Lotteries is just as likely.
.
Another way to think of the scenario..
After launch, the Tesla will be just as likely to impact Mars as any given Aten-class asteroid is.
(or whatever one calls an Aten-class asteroid, when speaking relative to Mars)
Expected impact rates of 1 in several hundred billion years, per asteroid.
refer http://www.bhporter.com/Porter%20PDF%20Files/Earth%20Crossing%20Asteroids.pdf for the math....

Offline cscott

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Nope, as the Tesla's orbital plane will not match Mars' orbital plane.
(it *cannot* do so for a launch now, without also needing a mid-course plane changing maneuver)

Technically, you could launch the payload on a great circle route up out of the ecliptic plane that would intersect Mars.  You can do that at any time, but the delta V costs can get extremely high.

See: http://hopsblog-hop.blogspot.com/2013/01/deboning-porkchop-plot.html

This is just a nit to pick. Your post is otherwise spot on. :)

Online FutureSpaceTourist

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Quote
Scooplet: Harrison Ford is heading down to Kennedy Space Center to view the #SpaceX Falcon Heavy launch next week. After all, it was named after his old ride.

https://twitter.com/nova_road/status/958369019115032578

Offline JonathanD

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Hopefully he's not flying himself this time #waywardplane

Offline Basto

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https://www.washingtonpost.com/news/the-switch/wp/2018/01/30/elon-musk-is-set-to-launch-his-falcon-heavy-rocket-a-flamethrower-of-another-sort/?utm_term=.636058d6f791

Some factual inaccuracies in there and no mention of the difference in performance of SLS vs FH.

But surprisingly fair for the source.

Offline envy887

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https://www.washingtonpost.com/news/the-switch/wp/2018/01/30/elon-musk-is-set-to-launch-his-falcon-heavy-rocket-a-flamethrower-of-another-sort/?utm_term=.636058d6f791

Some factual inaccuracies in there and no mention of the difference in performance of SLS vs FH.

But surprisingly fair for the source.

Looks like they hit on the difference:

Quote
SpaceX has said that the Falcon Heavy would cost $90 million a launch, a fraction of what NASA’s more powerful Space Launch System would cost.
Bold mine.

But yes, it's a very good summary of the situation at hand. Especially for WaPo.

Online gongora

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Since when has the Washington Post's coverage of SpaceX been bad?  They usually do a pretty good job in my view.

Offline macpacheco

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One argument against the direct insertion.
What capability SpaceX would like to demonstrate to customers ?
Long coast.
This is an upper stage feature (common to F9 and FH). So if SpaceX knows it can coast for 3 hours (just a guess), then why not demonstrate it ?
I think people are too obsessed with the Roadster and Mars and missing the big picture.
SpaceX is showing NASA, USAF, NRO, ... what the Falcon family of rockets can do. Its the first opportunity in a long time to show them off.
I'm suggesting this from a strictly business/marking view, technically I have no idea how it would impact the launch window and resulting orbit.
Looking for companies doing great things for much more than money

Offline Basto

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Since when has the Washington Post's coverage of SpaceX been bad?  They usually do a pretty good job in my view.

You are right. For some reason I was conflating WaPo with WSJ in my head.

Offline AncientU

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One argument against the direct insertion.
What capability SpaceX would like to demonstrate to customers ?
Long coast.
This is an upper stage feature (common to F9 and FH). So if SpaceX knows it can coast for 3 hours (just a guess), then why not demonstrate it ?
I think people are too obsessed with the Roadster and Mars and missing the big picture.
SpaceX is showing NASA, USAF, NRO, ... what the Falcon family of rockets can do. Its the first opportunity in a long time to show them off.
I'm suggesting this from a strictly business/marking view, technically I have no idea how it would impact the launch window and resulting orbit.

They've already demonstrated the long coast. 
This launch is to demonstrate the tri-core design performs as modeled and makes it to orbit... anything else is gravy.
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline Grandpa to Two

Since when has the Washington Post's coverage of SpaceX been bad?  They usually do a pretty good job in my view.

You are right. For some reason I was conflating WaPo with WSJ in my head.
I still have no idea of what WSJ IS.
"All truths are easy to understand once they are discovered; the point is to discover them" Galileo Galilei

Online tater

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Since when has the Washington Post's coverage of SpaceX been bad?  They usually do a pretty good job in my view.

You are right. For some reason I was conflating WaPo with WSJ in my head.
I still have no idea of what WSJ IS.

Wall Street Journal.

Offline OneSpeed

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To reduce the perigee from Earth to Venus, the minimum delta-V solution would require a retrograde burn at apogee, ie more energy.
Not true.  If your delta V was either directly towards the sun or away from it, the resulting heliocentric orbits would be very similar.  In both cases a single burn would result in an orbit with higher than Earth apogee and a lower than Earth perigee.

Kabloona and LouScheffer are correct, and that is not how a Hohmann transfer orbit works ( https://en.wikipedia.org/wiki/Hohmann_transfer_orbit ). A LEO burn away from the sun (at 6pm local time, over the terminator) raises the aphelion and leaves the perihelion unchanged. Burning towards the sun (at 6am local, also over the terminator) lowers the perihelion and leaves the aphelion unchanged.

So, by simply changing the timing of the FH Demo mission injection burn to 6am local, the roadster could just as easily be sent to a Venus heliocentric orbit.

Offline matthewkantar

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They've already demonstrated the long coast. 
This launch is to demonstrate the tri-core design performs as modeled and makes it to orbit... anything else is gravy.

Everyone loves gravy!

Offline mike robel

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edit:[The photos of the Falcons on the pads in the other thread] reminds me of these photos.  Looks like a Spaceport.  But the Falcons will both fly.
« Last Edit: 01/31/2018 03:14 am by mike robel »

Offline deruch

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Oh.  It looks like a Spaceport.  Reminds me of these pictures.


The difference is, of course, both these will fly.

If we get lucky with scheduling, in the future could it be possible to get a picture with 4 vehicles all on their pads at once?  SLS on LC-39B, F9/FH on LC-39A, Atlas 5/Vulcan on SLC-41, and F9 on SLC-40.  Given SpaceX's planned high cadence and the lengthy amount of time SLS is likely to be on the pad prior to launch, the deciding factor may be ULA's schedule on SLC-41. 
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline envy887

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Oh.  It looks like a Spaceport.  Reminds me of these pictures.


The difference is, of course, both these will fly.

If we get lucky with scheduling, in the future could it be possible to get a picture with 4 vehicles all on their pads at once?  SLS on LC-39B, F9/FH on LC-39A, Atlas 5/Vulcan on SLC-41, and F9 on SLC-40.  Given SpaceX's planned high cadence and the lengthy amount of time SLS is likely to be on the pad prior to launch, the deciding factor may be ULA's schedule on SLC-41.
DIVH should still be launching from 37 as well in 2019-2022.

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