SpaceX Tuesday...
Discussion
Landing a rocket vertically without the use of wings to help is very difficult - especially doing it pinpoint.
It seems that SpaceX make extensive use of software to provide the minute, precise and fast calculations needed to keep the plummeting tube aligned with the landing point.
The only aerodynamic assistance available to the falling stage comes from the grid fins - and these need minute adjustments, provided by the software, to ensure they function properly.
That type of technology did not exist in the 1960s and 1970s.
It seems that SpaceX make extensive use of software to provide the minute, precise and fast calculations needed to keep the plummeting tube aligned with the landing point.
The only aerodynamic assistance available to the falling stage comes from the grid fins - and these need minute adjustments, provided by the software, to ensure they function properly.
That type of technology did not exist in the 1960s and 1970s.
Eric Mc said:
Landing a rocket vertically without the use of wings to help is very difficult - especially doing it pinpoint.
It seems that SpaceX make extensive use of software to provide the minute, precise and fast calculations needed to keep the plummeting tube aligned with the landing point.
The only aerodynamic assistance available to the falling stage comes from the grid fins - and these need minute adjustments, provided by the software, to ensure they function properly.
That type of technology did not exist in the 1960s and 1970s.
So the moon landings were faked then?It seems that SpaceX make extensive use of software to provide the minute, precise and fast calculations needed to keep the plummeting tube aligned with the landing point.
The only aerodynamic assistance available to the falling stage comes from the grid fins - and these need minute adjustments, provided by the software, to ensure they function properly.
That type of technology did not exist in the 1960s and 1970s.
frisbee said:
So the moon landings were faked then?
You miss the point, each moon landing had two very biological super sophisticated computers on board over and above the fairly basic electronic computers on the Lunar Module. And even with two skilled pilots guiding the Lunar Module in to land, they did not have to be anything like as precise as a SpaceX booster has to be in order to land exactly on the "X" designator. In fact, Apollo 11 missed its intended touch down point by around 6 miles. Later Apollo landing were much more accurate but they still only needed to be around 100 meters or so from the designated spot.A more realistic comparison is the various robot landers that have landed on the moon, Mars, Venus and Titan. None of those have been anywhere remotely as accurate as a SpaceX booster landing - but they didn't need to be.
According to NASA JPL, the estimated landing ellipse for the Mars 2020 rover, which launched recently, is about 25 km long by 20 km wide. They say they may be able to get the ellipse down to 18 km long by 14 km wide.
Now of course the biggest part of that inaccuracy is due to the parachute element of the descent and that's why they have to be extremely picky about the landing area. They've managed to get the landing ellipse down greatly from older missions, but guided propulsive landing, a la SpaceX, would be pretty much essential to construct & support settlements there.
Now of course the biggest part of that inaccuracy is due to the parachute element of the descent and that's why they have to be extremely picky about the landing area. They've managed to get the landing ellipse down greatly from older missions, but guided propulsive landing, a la SpaceX, would be pretty much essential to construct & support settlements there.
Beati Dogu said:
According to NASA JPL, the estimated landing ellipse for the Mars 2020 rover, which launched recently, is about 25 km long by 20 km wide. They say they may be able to get the ellipse down to 18 km long by 14 km wide.
Now of course the biggest part of that inaccuracy is due to the parachute element of the descent and that's why they have to be extremely picky about the landing area. They've managed to get the landing ellipse down greatly from older missions, but guided propulsive landing, a la SpaceX, would be pretty much essential to construct & support settlements there.
Presumably atmospheric drag adds an additional level of complication that increases the size of the ellipse when landing on Mars compared to landing in a vacuum on the Moon.Now of course the biggest part of that inaccuracy is due to the parachute element of the descent and that's why they have to be extremely picky about the landing area. They've managed to get the landing ellipse down greatly from older missions, but guided propulsive landing, a la SpaceX, would be pretty much essential to construct & support settlements there.
(it does in KSP so t must be true
)RobDickinson said:
Eric Mc said:
Robotic landers have been arriving on the moon since 1966.
So they tell us.The discussion is the accuracy required for propulsive landings, without parachutes, on a solid body, such as the earth or the moon.
The accuracy requirements to do this on earth, which has an atmosphere, has a strong gravity field and has populated areas, are much more difficult than on an airless, unpopulated body like the moon.
The point I was making is that propulsive landings (manned and unmanned) have been made on the moon for over 50 years. The accuracy required for these landings was/is not as stringent as doing the same thing on earth.
Eric Mc said:
annodomini2 said:
Could probably do it with radio beacons.
Not good enough in the 1960s and 70s.GPS was the answer to accuracy - and even better when SpaceX could make of a system that was already in place and free to access.
1970's ICBMs were also accurate to 150m, so getting the booster close enough to allow terminal guidance was definitely possible.
I would suggest that the earliest you could have done propulsive landing of a booster was probably in the 1970's when digital fly by wire and relaxed stability was coming in.
Why they didn't do it:
1: The SpaceX development method falls down the gaps between expendable rocket thinking (trash it) and aircraft development. Re-usability advocates were thinking like aircraft designers where every aircraft is precious, manned and we'd prefer not to crash it. The idea of viewing an expendable booster as an opportunity to test re usability just wasn't on anyone's radar.
2: Propulsive landing is pretty mass inefficient, now we know that if you don't throw away the vehicle it doesn't matter if it is much larger. I did some quick calculations as to what a 1970's tech Falcon 9 would put into orbit:
16.5t expendable
8.5t ADLS
5.3t RTLS
Those are all LEO it would be worse to GTO
3: Guidance and navigation control was expensive as a minimum you have just doubled the cost as first and second stage both have have their own GNC, obviously the first stage GNC is also going to be massively more expensive as it has so many more tasks. You are then going to have to design and test all this without recourse to modern simulation.
4: Finally and by far the most important, politics and funding. The decisions on spending in the 1970's were made during the late 1960's. The next system had to fit in the existing budgets but it also had to have definable and costable budgets. The way things were procured and project managed and bidded simply wouldn't allow the iterative development required. During the space shuttle selection process they were very wary of interim designs less they be stuck with interim design for decades, as actually happened.
Talksteer said:
Look up Lorentz beam, this was sufficiently accurate to get a plane onto a runway blind in 1932. So long as the beam is on the landing location it gets progressively more accurate the closer you get. Could also do the final 20km with IR beacons and a sidewinder missile seeker. Cruise missiles were a 1970's technology.
1970's ICBMs were also accurate to 150m, so getting the booster close enough to allow terminal guidance was definitely possible.
I would suggest that the earliest you could have done propulsive landing of a booster was probably in the 1970's when digital fly by wire and relaxed stability was coming in.
Why they didn't do it:
1: The SpaceX development method falls down the gaps between expendable rocket thinking (trash it) and aircraft development. Re-usability advocates were thinking like aircraft designers where every aircraft is precious, manned and we'd prefer not to crash it. The idea of viewing an expendable booster as an opportunity to test re usability just wasn't on anyone's radar.
2: Propulsive landing is pretty mass inefficient, now we know that if you don't throw away the vehicle it doesn't matter if it is much larger. I did some quick calculations as to what a 1970's tech Falcon 9 would put into orbit:
16.5t expendable
8.5t ADLS
5.3t RTLS
Those are all LEO it would be worse to GTO
3: Guidance and navigation control was expensive as a minimum you have just doubled the cost as first and second stage both have have their own GNC, obviously the first stage GNC is also going to be massively more expensive as it has so many more tasks. You are then going to have to design and test all this without recourse to modern simulation.
4: Finally and by far the most important, politics and funding. The decisions on spending in the 1970's were made during the late 1960's. The next system had to fit in the existing budgets but it also had to have definable and costable budgets. The way things were procured and project managed and bidded simply wouldn't allow the iterative development required. During the space shuttle selection process they were very wary of interim designs less they be stuck with interim design for decades, as actually happened.
They did opt for precision landing in the early 1970s. It was called the Space Shuttle. As I have said quite a few times on various space threads, the Space Shuttle actually stymied and held back progress in other areas of rocket and spacecraft development.1970's ICBMs were also accurate to 150m, so getting the booster close enough to allow terminal guidance was definitely possible.
I would suggest that the earliest you could have done propulsive landing of a booster was probably in the 1970's when digital fly by wire and relaxed stability was coming in.
Why they didn't do it:
1: The SpaceX development method falls down the gaps between expendable rocket thinking (trash it) and aircraft development. Re-usability advocates were thinking like aircraft designers where every aircraft is precious, manned and we'd prefer not to crash it. The idea of viewing an expendable booster as an opportunity to test re usability just wasn't on anyone's radar.
2: Propulsive landing is pretty mass inefficient, now we know that if you don't throw away the vehicle it doesn't matter if it is much larger. I did some quick calculations as to what a 1970's tech Falcon 9 would put into orbit:
16.5t expendable
8.5t ADLS
5.3t RTLS
Those are all LEO it would be worse to GTO
3: Guidance and navigation control was expensive as a minimum you have just doubled the cost as first and second stage both have have their own GNC, obviously the first stage GNC is also going to be massively more expensive as it has so many more tasks. You are then going to have to design and test all this without recourse to modern simulation.
4: Finally and by far the most important, politics and funding. The decisions on spending in the 1970's were made during the late 1960's. The next system had to fit in the existing budgets but it also had to have definable and costable budgets. The way things were procured and project managed and bidded simply wouldn't allow the iterative development required. During the space shuttle selection process they were very wary of interim designs less they be stuck with interim design for decades, as actually happened.
Between 1972 and 1986, the American rocket manufacturers had been told that by the mid 1980s ALL American launches would be on the Shuttle.
The go ahead to start putting conventional boosters back into production only came about because of the Challenger accident.
I suspect a big part of the reusability drive comes from Musk's obsession with Mars. Getting home from the moon is pretty simple - leave most of the mass behind and have a small rocket boost you off the surface. Getting home from "proper" planets is much harder. You have two choices - either build a launch and development infrastructure that looks a lot like that on Earth, or you make sure that the bus that brought you can get you home as well.
Building Cape Canaveral on Mars would be rather difficult, and then you've got to build a rocket factory. Or you learn how to land a rocket in the launch position. If you can do that, all you need is enough fuel to get home.
The tech to do this has come on in leaps and bounds in the last decade - it is almost commodity now. My cheap Chinse drone has almost all of the tech to do this in a few integrated circuits and sensors. In the 70s, this would be a material engineering innovation in its own right. Clearly you need to scale the drone tech and make it much more reliable, but it is at least a solved problem.
The relative inefficiency of reuse doesn't really matter if you get launch costs down by two orders of magnitude. So what if you can only lift 70% of the payload - you can launch 100 rockets for the same price.
Building Cape Canaveral on Mars would be rather difficult, and then you've got to build a rocket factory. Or you learn how to land a rocket in the launch position. If you can do that, all you need is enough fuel to get home.
The tech to do this has come on in leaps and bounds in the last decade - it is almost commodity now. My cheap Chinse drone has almost all of the tech to do this in a few integrated circuits and sensors. In the 70s, this would be a material engineering innovation in its own right. Clearly you need to scale the drone tech and make it much more reliable, but it is at least a solved problem.
The relative inefficiency of reuse doesn't really matter if you get launch costs down by two orders of magnitude. So what if you can only lift 70% of the payload - you can launch 100 rockets for the same price.
Beati Dogu said:
What looks like launch tower foundations are being constructed at Boca Chica on top of earlier pilings:
Elon has confirmed this structure will be the "Orbital launch mount", not a water tower as many have suggested. Makes sense, as it's on the seaward site of the site.SN6 did a static fire OK last night, so they'll be fitting a mass simulator to the top soon and go flying in a week or two.
Anyone notice the googly eyes on its Raptor engine:
Taken from a much larger image here:
https://forum.nasaspaceflight.com/index.php?action...
SpaceX are attempting to launch two Falcon 9s in the space of 9 hours at the weekend.
It's dependent on the ULA Delta IV Heavy mission getting away on Saturday morning (7:04 am UK time) without further delays.
With that gone, the authorities can reconfigure the range (radar, tracking etc) for SpaceX, which takes them about a day.
So on Sunday:
1) Starlink-11 from pad LC-39A at 10:12 am local (3.12 pm UK time). The landing ship it on it's way to station currently.
Followed by:
2) SAOCOM-1B from pad SLC-40 at 7:19 pm local (12:19 am UK time on Monday morning)
This one will be the first southbound rocket from Cape Canaveral since 1960 (because of Cuba). It'll launch eastwards as usual, but dog leg* south as it does so. It's not a heavy payload, so they'll try and land the booster back at the Cape shortly after. The faring recovery area is south of Miami.
They're sending one fairing capture boat to each recovery area. Each boat is capable of recovering both fairing halves (one from the air and one (or both) from the water).
There may also be a 150 meter hop from Starship SN6 at the weekend too.
.*SpaceX used the name Dogleg Park LLC as the shell company when they were initially buying land at Boca Chica.
It's dependent on the ULA Delta IV Heavy mission getting away on Saturday morning (7:04 am UK time) without further delays.
With that gone, the authorities can reconfigure the range (radar, tracking etc) for SpaceX, which takes them about a day.
So on Sunday:
1) Starlink-11 from pad LC-39A at 10:12 am local (3.12 pm UK time). The landing ship it on it's way to station currently.
Followed by:
2) SAOCOM-1B from pad SLC-40 at 7:19 pm local (12:19 am UK time on Monday morning)
This one will be the first southbound rocket from Cape Canaveral since 1960 (because of Cuba). It'll launch eastwards as usual, but dog leg* south as it does so. It's not a heavy payload, so they'll try and land the booster back at the Cape shortly after. The faring recovery area is south of Miami.
They're sending one fairing capture boat to each recovery area. Each boat is capable of recovering both fairing halves (one from the air and one (or both) from the water).
There may also be a 150 meter hop from Starship SN6 at the weekend too.
.*SpaceX used the name Dogleg Park LLC as the shell company when they were initially buying land at Boca Chica.
Old news but just to say how important this is
https://techcrunch.com/2020/08/18/spacex-raises-1-...
I guess that Japanese bloke who asked for a space bride ran out of money.
Starlink is the biggest money spinner here potentially, less so on transferring objects including people up into LEO and finally the dodo that is stainless steel ships that can land again after orbiting. He's never going to be able to do that, bitten off more than they can chew. They just don't know it yet.
https://techcrunch.com/2020/08/18/spacex-raises-1-...
I guess that Japanese bloke who asked for a space bride ran out of money.
Starlink is the biggest money spinner here potentially, less so on transferring objects including people up into LEO and finally the dodo that is stainless steel ships that can land again after orbiting. He's never going to be able to do that, bitten off more than they can chew. They just don't know it yet.
Edited by Gandahar on Friday 28th August 20:02
Well, we'll see about that.
If it has an achilles heel, I think it'll be the heat shield tiles.They were the bane of the Shuttle too. If they can solve that, I think they'll be OK.
They'll be starting the build booster prototypes soon and take some of those flying. With only 2 engines at first apparently.
If it has an achilles heel, I think it'll be the heat shield tiles.They were the bane of the Shuttle too. If they can solve that, I think they'll be OK.
They'll be starting the build booster prototypes soon and take some of those flying. With only 2 engines at first apparently.
Gandahar said:
Old news but just to say how important this is
https://techcrunch.com/2020/08/18/spacex-raises-1-...
I guess that Japanese bloke who asked for a space bride ran out of money.
Starlink is the biggest money spinner here potentially, less so on transferring objects including people up into LEO and finally the dodo that is stainless steel ships that can land again after orbiting. He's never going to be able to do that, bitten off more than they can chew. They just don't know it yet.
Well that is a cheerful thought. Um. Are Atlas rockets not made of stainless steel? And the Shuttle SRBs were steel ... they "landed" too. So it's the "after orbiting" bit that you're not happy with? https://techcrunch.com/2020/08/18/spacex-raises-1-...
I guess that Japanese bloke who asked for a space bride ran out of money.
Starlink is the biggest money spinner here potentially, less so on transferring objects including people up into LEO and finally the dodo that is stainless steel ships that can land again after orbiting. He's never going to be able to do that, bitten off more than they can chew. They just don't know it yet.
Edited by Gandahar on Friday 28th August 20:02
Gandahar said:
...
Starlink is the biggest money spinner here potentially, less so on transferring objects including people up into LEO and finally the dodo that is stainless steel ships that can land again after orbiting. He's never going to be able to do that, bitten off more than they can chew. They just don't know it yet.
The Space Shuttle was mostly made of Aluminium, SS has better high temp properties than aluminium.Starlink is the biggest money spinner here potentially, less so on transferring objects including people up into LEO and finally the dodo that is stainless steel ships that can land again after orbiting. He's never going to be able to do that, bitten off more than they can chew. They just don't know it yet.
So unless you are just spouting FUD and care to back up your claims?
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