Falcon Heavy Assembly Underway

louis · 2017-12-29 21:32:43

I have total confidence in Musk on this one.

RobertDyck · 2017-12-29 21:35:08

Oldfart1939 wrote:

Getting back on track with the Falcon Heavy; here's the link to spacefilghtinsider story on Falcon Heavy raised to vertical on LC-39a.

SpaceNut · 2017-12-29 22:51:18

Sounds like a constellation of cube sat's would be the ticket for just GPS....

louis · 2017-12-30 08:21:20

Thanks for the tutorial Robert - very helpful.

RobertDyck wrote:

There is a Mars relay antenna on Odyssey, MRO, Mars Express, and MAVEN. It can relay data from a lander or rover, and can be used to measure range (distance) from orbiter to lander/rover. With 3 satellites, or 3 measurements from the same satellite over enough time that rotation of the planet moves the lander/rover to a new location, you can calculate exact position by intersecting spheres. It's not nearly as precise as GPS, but is something.
I believe it computes range by calculating time for a signal from rover to orbiter. Multiply by speed of light gives you distance. Using the precise topography map of Mars produced by the laser altimeter, intersection will give you a ring. Then calculate angle to the orbiter based on signal Doppler shift, together with known speed and position of the orbiter. That will give you two possible positions for the lander/rover, one to the left of the orbiter, the other to the right. A second measurement with the orbiter has moved could tell you which one, or just assume the lander/rover is in the same hemisphere of Mars where it landed.
I've been told some of the extreme technology in GPS satellites that give them extreme precision. Mars orbiters don't have that.
Mars Reconnaissance Orbiter: Electra
Electra is a telecommunications package that acts as a communications relay and navigation aid for Mars spacecraft.
Toward the end of the primary science phase, other Mars missions launched in 2007 and beyond will begin to arrive. Mars Reconnaissance Orbiter will use its Electra UHF radio to support any navigation, command, and data-return needs these missions may have. If the arriving spacecraft has an Electra communications payload, it can receive these signals and use them to determine its distance and speed in relation to Mars. This communication allows much more precise navigation.
After incoming landers or rovers have arrived safely on Mars, Electra can provide precise Doppler data which, when combined with Mars Reconnaissance Orbiter's position information, can accurately determine the location of the lander or rover on the surface of Mars.
Electra can also provide UHF coverage to Mars landers and rovers on the surface that may not have sufficient radio power to communicate directly with Earth by themselves, using its nadir-pointed (pointed straight down at the surface) antenna.

Oldfart1939 · 2017-12-30 10:20:34

A complete constellation of small GPS satellites is absolutely essential for landing accuracy and precision. To accomplish what Musk hopes to do will also require ground-based transponders. In effect, a Martian WAAS system. I fly privately, and my personal airplane is equipped with a Garmin GNS530W, which is capable of flying approaches in IFR conditions. The big airliners are all equipped with auto-land avionics, and the WAAS system controls the landings. Some US airports REQUIRE that pilots use the auto-land feature regardless of visibility conditions after the debacle in San Francisco with the KAL airliner that came up short on the approach.

RobertDyck · 2017-12-30 11:58:06

I read about Gravity Probe B. It measured frame dragging caused by Earth's rotation. The effect is so slight that it required extreme precision to detect it. They had to invent several new technologies for it to work. One was a quartz ball that floated free in a sealed vacuum chamber on the satellite. Laser range finders would measure position of the quartz ball within the chamber. The satellite was in low Earth orbit, 640 km altitude, so there was still a little drag from atmosphere. The ball had to be non-metallic so the Earth's magnetic field wouldn't affect it. The quartz ball was in a vacuum chamber so in perfect orbit about the Earth, the satellite used thrusters to adjust it's position around the quartz ball. Variations in Earth's density (mountains, etc) caused variations in gravity that affected the satellite's orbit, but nothing else. Before Gravity Probe B was launched, GPS satellites used this technology to keep their orbit exact. Mars orbiters don't have this.

A modern smart phone has a GPS receiver that can give your position ±4 metres. Using a differential, professional and military GPS can get it down to less than one metre. I could explain how a differential works, but the point is Mars orbiters don't have any of this. Expect margin of error to be much greater.

Ps. A couple years ago someone wrote an Android app that turns your smart phone into a tricorder. It reports actual real data from sensors on your smart phone, presenting them using the LCARS interface from Star Trek TNG/DS9/Voyager. It actually doesn't provide any practical information, but it's cool! One thing is your exact location in latitude and longitude down to the milli-minute of degree. That's thousandth of a minute, not seconds. It also shows altitude to 1/10th of a metre, and magnetic compass gives heading. It shows GPS satellites in view, my phone sees 12 or 13 from my location. It shows satellite positions in the sky, updated in real time. My point is there are 31 GPS satellites in Earth orbit, Mars has only 4. So how many Mars orbiters are in view at any given time?

Here's a screen shot of the tricorder app. The programmer made it available free, but Paramount lawyers demanded she take it down. I grabbed a copy of the installation file before it was deleted. I got a smart phone last November; the tricorder install file is from 2011, but it still worked. The screen shot is from 2010, my copy is a year newer.

Oldfart1939 · 2017-12-30 13:20:33

Rob-

The military grade GPS systems are down to less than a meter in accuracy; it's more like a few centimeters. The stated accuracy of a Garmin GNS530W is one meter.

Last edited by Oldfart1939 (2017-12-30 13:21:20)

RobertDyck · 2017-12-30 14:36:01

This is why several of us argue for a homing beacon. Place a transmitter on the ground at the base location, future landers will use that rather than satellites.

Oldfart1939 · 2017-12-30 15:59:03

You're talking about an ADF system, which is far less sophisticated than transponders embedded in the GPS-WAAS systems. Elon wants to land within a meter of the predetermined touchdown point. For private aircraft, many no longer incorporate an ADF in their avionics stack. Mine doesn't have one anymore, since I upgraded to the Garmin system.

RobertDyck · 2017-12-30 17:43:12

That's fine on a planet that has GPS and WAAS. I had to look up what WAAS is. In 2001 I worked for a company that produced software for a manufacturer of a real-time GPS mapping system for a crop dusting aircraft. It used a differential. That's a device on a building or other known static ground location, with a GPS receiver. It compares GPS coordinates with it's known location, and transmits to local devices the adjustment. This is how you get sub-metre accuracy, within just a few centimetres. WAAS is a system that takes data from differential receivers all over the continent, relays their data through a geostationary satellite. So you don't have to be within short-range radio range of the differential. Ok, brilliant, but that requires many differential receivers all over the continent, internet to collect their data to a central server, a satellite uplink, and a geostationary satellite to broadcast that data. We don't have all that infrastructure on Mars. We have 4 orbiters. An "Automatic Direction Finder" or ADF would be a great improvement over what we have now. Yes, ADF on an aircraft uses the signal from a Non-Directional Beacon (NDB) on the ground. We are talking about placing an NDB on Mars for ADF equipment. Aircraft also have Instrument Landing System (ILS), and the upgrade from that is Microwave Landing System (MLS). The last one allows curved approaches to the airport. We can look at all these to come up with an advanced system for Mars. But we don't have a constellation of GPS satellites orbiting Mars, and we certainly won't have the massive ground infrastructure required for WAAS. So if we can miniaturize a beacon system, that would work. MLS was developed in the 1970s, could a phased-array transmitter provide precise guidance to a lander while still being small enough to be practical?

Oldfart1939 · 2017-12-30 18:39:44

Probably one of the things we could get OldSpace to do with their throwaway rocket is installation of a GPS constellation around Mars. A NDB would work OK in conjunction with the GPS satellite system. The GPS constellation would do the guidance to a distance from which a NDB would give a location that would be well-defined w/r GPS coordinates. Even the first landing would benefit from this system.

louis · 2017-12-30 18:59:35

Yes...or maybe a really efficient data transmission chain from Mars to Earth? So we can do some serious data transfer.

Oldfart1939 wrote:

Probably one of the things we could get OldSpace to do with their throwaway rocket is installation of a GPS constellation around Mars. A NDB would work OK in conjunction with the GPS satellite system. The GPS constellation would do the guidance to a distance from which a NDB would give a location that would be well-defined w/r GPS coordinates. Even the first landing would benefit from this system.

SpaceNut · 2017-12-30 20:36:48

2018 launch http://www.spaceflightinsider.com/launch-schedule/

Jan 15 Falcon Heavy Test Flight

TBD Space Test Program-2 (STP-2) mission

So provided that all goes well just the 2 shake down in 2018 launches of the heavy

Oldfart1939 · 2017-12-30 22:23:09

This is also listed as 15 January 2018 on spaceflight101.com launch manifest.

I suspect there could be more flights if all proceeds without any significant issues. The 2 guys around the Moon?

SpaceNut · 2017-12-31 22:25:42

From the BFR link http://www.spacex.com/sites/spacex/file … y-2017.pdf slide 7 shows that Falcon 9 launches as being less than what was expected in 2017 so the even higher level in 2018 I think is going to be way off as well...

Oldfart1939 · 2017-12-31 22:48:33

SpaceNut-
I believe that the lowered number of launches than anticipated was due to turnaround time of the launch pad facility. SpaceX now has 2 pads at Cape Canaveral instead of one. LC-39a, and LC-40. That alone will increase the launch rate, should they be able to continue re-use of the first stages recovered. Earlier, the production of Falcon 9 rockets was the rate limiting factor.

SpaceNut · 2018-01-01 21:55:01

I hope thats true and I also hope that something is in between the heavy and bfr are on the table as well as the amount of fuel to create is outside of the solar deployable limits I fear.

Oldfart1939 · 2018-01-01 22:32:33

SpaceNut-

Last year I proposed an intermediate architecture based on an enlarged Dragon 2 spacecraft and requiring the Falcon X Heavy. That approach still sounds reasonable as a bridging step between Falcon Heavy and the BFR. We need successful manned and unmanned landings and establishment of a base as an enabler of the fuel production for BFR.

SpaceNut · 2018-01-01 23:06:50

How would I scale the ship size if we are looking to only return to orbit with a few tons at most of payload? Fuel used to land the ship needs to only land a full payload for the return to orbit condition.

Zubrin's original sums gave an energy input of 17 MwHs per tonne of propellant. If BFR requires 1500 tonnes of the propellant, that would imply an energy input of 25500 MwHs or, over 660 sols, an input of 38.64 MwHs or about 1.6 Mw constant.

say a more modest payload landed is support for crew of 10 ton possibly does the fuel required scale to 100 ton to launch the ship back to orbit

RobS · 2018-01-03 22:42:14

I was just looking at the Falcon Heavy wiki https://en.wikipedia.org/wiki/Falcon_Heavy and was surprised to see that the payload to LEO is now listed as 63.8 tonnes and to Mars, 16.8 tonnes! The LEO figure is now 10% less than the SLS, which renders it even less useful and significant. If Space X wanted to, I am sure they could push it over 70 tonnes; just add a larger second stage. But of course they're turning to the BFR instead.

RobertDyck · 2018-01-03 23:55:09

It was originally 53 tonnes to LEO. Then 54 tonnes. Now 63.8 tonnes to LEO. That is an increase. It never was designed to lift more than SLS block 1. The fact it's getting close is significant.

louis · 2018-01-04 09:03:54

Is it true there's a Florida Freeze? Will this affect launch?

SpaceNut · 2018-01-04 11:36:31

I would think not as they are not using any SRB orings..yes parts of florida did see snow and I am being hit with a blizard and at a minimum 12 inches...will fire up the wood stove later as I only have so much wood due to not expecting furnace to fail....available wood is green and does not burn....

Nice that the payload is ramping up but they really need to get a larger core as 3.7 meters is not going to cut it....

elderflower · 2018-01-05 04:36:54

I don't think I would test the engines in very low temperatures, let alone launch the Falcon Heavy. There is no time pressure. The aliens are probably not waiting to snap up a little red automobile.
Stay warm, Spacenut.

louis · 2018-01-05 07:19:02

Trying to put the jigsaw pieces together, if the propellant production doesn't begin until humans arrive in 2024, then I can only assume the pioneers will assemble the propellant tanks...they might well do this robotically working from inside pressurised rovers.

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