totm nov 2023 SpaceX Discussion Thread

[grungar3x7]

@DAL59

Every time I see that video, I find myself screaming at the monitor, "EXECUTE ROLL PROGRAM, FOR GODDARD'S SAKE!!"

[tater]

 

[cubinator]

1 hour ago, DAL59 said:

 

I can already tell...during final descent I'll be making one of these faces:

(Hint: it's either the one on the left or the one on the right.)

I'm not comfortable with the idea of flipping around while plummeting towards the ground inside a rocket, but pfft. It's only seven minutes of my life and anything that ends in me being on Mars is a win in my book.

[sevenperforce]

1 hour ago, grungar3x7 said:

@DAL59

Every time I see that video, I find myself screaming at the monitor, "EXECUTE ROLL PROGRAM, FOR GODDARD'S SAKE!!"

Gravity drag on Mars is cheap. Delta-V is not.

[grungar3x7]

26 minutes ago, sevenperforce said:

Gravity drag on Mars is cheap. Delta-V is not.

I mean that the spacecraft should be entering atmosphere inverted, nose down, like in the Adelaide presentation.

 

[kerbiloid]

Landing for two minutes at ~1g acceleration and with heads down?
Sounds a little like "face is red, they are dead".

***

12 000 sats in LEO and Kessler syndrome?
No problem, it will be renamed.

***

This was first.

Spoiler

This was next.

Spoiler

This is what really happened at last.

Spoiler

 

[YNM]

10 hours ago, DAL59 said:

Wait, what?  How are they going to launch 12,000 satelites if they only do two at a time?  

12,000 satellites !!?!?! What, one for every 200 km sided patch of land ? How in the bloody hell are we going to launch anything else ?

Seriously, just put some good olde BTS towers if that's the order !!! Go get 5G or something !

Edited February 16, 2018 by YNM

[NSEP]

1 hour ago, YNM said:

12,000 satellites !!?!?! What, one for every 200 km sided patch of land ? How in the bloody hell are we going to launch anything else ?

Seriously, just put some good olde BTS towers if that's the order !!! Go get 5G or something !

Someone is going to get mad one day and will develop a space warship to deorbit all those satellites.

Okay but seriously, i bet the satellites have their own propulsion system (otherwise they can't stay on Low Orbit and will eventually come back down and burn up), so if people start worrying about the Starlink fleet, Elon can just push the ok i changed my mind button and have those sats come down and get destroyed.

Or they can cancel it...

Edited February 16, 2018 by NSEP

[CatastrophicFailure]

2 hours ago, YNM said:

12,000 satellites !!?!?! What, one for every 200 km sided patch of land ? How in the bloody hell are we going to launch anything else ?

Seriously, just put some good olde BTS towers if that's the order !!! Go get 5G or something !

Because they're not much more than cubesats and they can launch dozens at once. Also, the initial bunch is "only" around 4000. And with "24 hours" turn-around time on Block 5, all they have to do is crank out upper stages...

I may be an early adopter. I'm lucky to even get one bar of 1G where I am, and the only internet choices are the local phone company, which sucks, and the big nationwide cable company, which sucks but has decent speed. IF I can get equal/better speed, at a competitive price, AND give money to SpaceX (via its subsidiary), sign me up!

Oh, also, StarLink isn't the only player in the game. There's one or two others also looking to loft internet satellite constellations numbering in the thousands. 

[YNM]

15 minutes ago, CatastrophicFailure said:

Because they're not much more than cubesats

What bandwith are they looking ? 1 Tbit ? I bet not.

In which case, b0llocks. Undersea cables can easily go beyond that.

Edited February 16, 2018 by YNM

[CatastrophicFailure]

3 minutes ago, YNM said:

What bandwith are they looking ? 1 Tbit ? I bet not.

In which case, b0llocks. Undersea cables can easily go beyond that.

Musk has only said "ultra-high-speed," whatever that means remains to be seen. But I think you're missing the point, this isn't meant for everyone, it's meant for users in areas not well served by traditional services, and to give some competition where it is (and where there is often none). Might not be the best thing for gamers if the lag is what's been discussed, but for the average user who just facebooks and streams movies? Yeah, it's possibly an option. And any competition would be in improvement at this point.

[YNM]

3 minutes ago, CatastrophicFailure said:

it's meant for users in areas not well served by traditional services, and to give some competition where it is (and where there is often none).

Then you've just made 12,000 cubesats obsolete in short time because now they'll want cables.

Seriously Elon, if you want people to get internet, get a fixed link, not a bodge.

[Green Baron]

7 minutes ago, YNM said:

Then you've just made 12,000 cubesats obsolete in short time because now they'll want cables.

Seriously Elon, if you want people to get internet, get a fixed link, not a bodge.

Nope. This is a good idea from Musk. Nobody will lay cables to the place where i live for example. The towns have cables, but out in the fields you either have a radio connection to a central antenna (i tried out the provider, they are bad) or satellite. Satellite is ok, but if it had competition they'd do much better.

Problem: Satellite is in GSO. Which means 0.2 seconds for up and down communication. A dynamically built page that asks many ad servers, google, facebook, youtube and all those so-called social things takes time. I mean TIME, like 20-30 seconds or more. I can block outgoing calls to those annoying services from my network, but that only counts for a half. Downloads of continuous data like updates etc. otoh are relatively fast (the contracted speed actually).

So, if spacex would actually provide that service for reasonable conditions (like less than 30funds/month, >3Mbit/s, more than 30GB/month or better unlimited) i'd be a customer.

 

[Elthy]

Also dont forget ships and planes. Both will pay a lot for good internet...

 

If they realy want to build 12000 satellites they need a dedicated factory and lots of automatition. It will be exciting to see economics of scale at work.

Edited February 16, 2018 by Elthy

[CatastrophicFailure]

31 minutes ago, YNM said:

Then you've just made 12,000 cubesats obsolete in short time because now they'll want cables.

Seriously Elon, if you want people to get internet, get a fixed link, not a bodge.

Like the other guys said, laying a cable isn't always an option. Or maybe there's ONE option for a cable, and nobody wants it, cuz the provider sucks, and can continue to suck as long as they have their little monopoly. Not everyone lives in a city, bruh. 

 

7 minutes ago, Elthy said:

Also dont forget ships and planes. Both will pay a lot for good internet...

That too. Bet there's a lot of demand on those cruise ships with thousands of people on board...

8 minutes ago, Elthy said:

If they realy want to build 12000 satellites they need a dedicated factory and lots of automatition. It will be exciting to see economics of scale at work.

As I understand, they're looking to build it out here in Kent, WA near their lab facility. My wife keeps checking the job postings there, and I keep reminding her what the commute would be like. 

Landline-speed internet in the vanpool, now there's a good use of it...

[Green Baron]

The main thing will be to find enough customers that the whole thing actually pays. They should do a study to find out if there are enough people wanting and willing, if that has not been done already. Not that it goes like Tesla ...

Musk's example of Africa is beyond reality (as usual i am tempted to say), few people away from the population centers actually have money and even fewer for something like an internet connection and the necessary power supply.

Edited February 16, 2018 by Green Baron

[YNM]

@Green Baron@Elthy@CatastrophicFailure

Here's what I challenge it with : Standard radio telephone. LTE can reach Gbit/s (alright, probably not far away from the transmitter). The infra is there ; carriers just need to upgrade their equipment. There's no need to overcrowd anything.

Sure, people in remote islands would probably not get one, but you'd be amazed by how many islands already have their cables.

And for Africa, actually phones are pretty common, and their technology are very useful in many ends (ie. SMS-based financial service). If they need the .net, they probably don't need high-speed, low-latency one yet, all that could be covered under 2G even (I have accessed and loggrd in to this forum from a nokia XD). Again, increase in speed could be done simply by upgrades of the network.

I know they're trying to change stuff by getting in the competition, but thrashing unknown stuff into the "unknown" is probably not the smartest of ideas. TEL and CFC were revolutionary, sure, but it's ironical to see them as a good idea now. (extra irony from the fact they're introduced by the same person !)

[Nefrums]

2 hours ago, Green Baron said:

Musk's example of Africa is beyond reality (as usual i am tempted to say), few people away from the population centers actually have money and even fewer for something like an internet connection and the necessary power supply.

I think you need to update you information sources on that,  It looks like they are 20 years out off date..

 

I think Musk knows hat he is doing.  Wireless telecom is a trillion $ yearly market. He don't need to get that much of a market share to make up for a few hundreds billions in investment costs.   

 

 

[Gkirmathal]

On 2/13/2018 at 12:57 AM, DAL59 said:

Hmm... I know this isn't going to happen, but it would be very nice to to have a 50th anniversery moon landing.  

50 years after Apollo 11, and we still only have up to 6 people in space.  Sigh.  

I really watching enjoyed this and it made me wonder if it were remotely possible with some redesigning of F9 2nd stage and D2 trunk. Been building Munar mission in my 6.4x KSP install with SSTU and real fuels. On that scale it in KSP it seems doable.

So, funding issues for such endeavor aside.
Could it be technically feasible for SpaceX to:
a) rework their second stage into a multiple reusable and refuel-able TLI tug?; and
b) add fuel tanks + propulsion to the D2 trunk to make it capable to do trans Lunar injection burn with a lander and the TEI burn to get home?

[Green Baron]

2 hours ago, YNM said:

Here's what I challenge it with : Standard radio telephone. LTE can reach Gbit/s (alright, probably not far away from the transmitter). The infra is there ; carriers just need to upgrade their equipment. There's no need to overcrowd anything.

Nope, no infrastructure. Not even high speed GSM or terrestrial DSL. You need the masts, transmitters and the cable or satellite connection to get the data away. Enormous investments that the big companies like Vodaphone, Orange, Movistar etc. don't do. Not even in rural Germany, and guaranteed not on an Atlantic Island. Not for let's say 50 or 100 potential customers per mast.

Again: in the villages and towns, yes. Since last year the fibreoptic cable from the mainland via Tenerife goes until Los Llanos de Aridane. ADSL is available too there, but not out in the fields.

2 hours ago, YNM said:

Sure, people in remote islands would probably not get one, but you'd be amazed by how many islands already have their cables.

See above :-) Since last year, but only the town.

2 hours ago, YNM said:

And for Africa, actually phones are pretty common, and their technology are very useful in many ends (ie. SMS-based financial service). If they need the .net, they probably don't need high-speed, low-latency one yet, all that could be covered under 2G even (I have accessed and loggrd in to this forum from a nokia XD). Again, increase in speed could be done simply by upgrades of the network.

I have seen people in Africa (East Africa, Tansania, Kenya) run around with black painted cardboxes, playing mobile phone. And many without nothing. In relatively densely populated areas. Away from the centers things are different, people are poor and infrastructure is bad to non-existent. Those who have phones and live in an area with coverage don't care for a satellite network, those who have nothing must care for different and more basal things than celestial internet. That's the sad reality in many places. Direct investments are discouraged and the "official" ones frequently end up ... well i don't want to summon the moderators who are quite strict when it comes to politics :-)

 

Whatever. The company that offers such a service has to demonstrate first that they can deliver and that they don't walk a constant borderline to bankruptcy. Then we'll see. Well, first they actually have to build that Kessler-network :-)

49 minutes ago, Nefrums said:

I think you need to update you information sources on that,  It looks like they are 20 years out off date..

7 :-)

[Nefrums]

I still doubt your sources on this. @Green Baron

Where have you gotten this information from? 

According to https://data.worldbank.org/indicator/IT.CEL.SETS.P2 the number of cell phones per person is not that different between most countries any more.

[Green Baron]

I was there.

 

Edit: you live in Scandinavia, @Nefrums, one of the if not the most egalitarian society in the world. You never see much difference between rich and poor, i daresay you don't have poor people in a sense that they can't afford basic clothing and food. The poor people there drive fried out cars and use the penultimate generation of phones, but they have cars and phones

In many parts of the world the differences between rich and poor are much greater. Once away from the city centers you see the gradient. I bet it'll make you feel uncomfortable when you see it.

Back on topic: the people Musk wants to reach aren't necessarily wealthy clients with computers, electricity and a necessity of high speed internet access as a primary requirement. And if his company doesn't find enough customers to finance the upkeep of such a network it'll be gone soon(tm).

I mean, we already have celestial internet at reasonable speeds, this isn't new what he plans, but it is imo a good step towards competition. I have satellite internet. He must do better than that ! Let's see if his "yet another funny company" Starlink - thanks @sh1pman who mentioned that below - can ;-)

Edited February 16, 2018 by Green Baron

[sh1pman]

PAZ badge. No sign of Starlink sats though.

[sevenperforce]

1 hour ago, Gkirmathal said:

I really watching enjoyed this and it made me wonder if it were remotely possible with some redesigning of F9 2nd stage and D2 trunk. Been building Munar mission in my 6.4x KSP install with SSTU and real fuels. On that scale it in KSP it seems doable.

So, funding issues for such endeavor aside.
Could it be technically feasible for SpaceX to:
a) rework their second stage into a multiple reusable and refuel-able TLI tug?; and
b) add fuel tanks + propulsion to the D2 trunk to make it capable to do trans Lunar injection burn with a lander and the TEI burn to get home?

Propellant transfer on the Falcon upper stage is not really feasible, since the tanks use helium for ullage pressure. I mean, automated high-pressure helium transfer could be done, but it would be an immense, immense redesign.

Orbital docking and upper-stage extended restarts, on the other hand, are definitely feasible.

A Draco-based propulsion assist pallet, mated to the payload adapter inside the D2 trunk, could provide enough dV for the burn out of Lunar orbit and onto an Earth entry trajectory. The same propulsion pallet on a stripped-down D2 could provide enough dV for single-stage ascent off of the moon, though TWR would be insufficient. You'd want to use Joint Lunar Orbit Rendezvous rather than Earth Orbit Rendezvous, though.

I have started crunching the numbers on this, and so the profiles may need to be adjusted slightly depending on dV, but the overall plan is solid.

1. Launch crew on a standard Dragon 2 with a propulsion assist pallet in the trunk, using an ASDS-recovered Falcon 9, into LEO.
2. Launch an ASDS-recovery Falcon 9 carrying only an international docking adapter, with a slightly-modified upper stage to allow for boiloff protection and extended restarts, into LEO.
3. Use Dragon 2's OMS to rendezvous and dock, nose-to-nose, with the IDA on the business end of the Falcon 9 upper stage.
4. Use the Falcon 9 upper stage to perform the TLI burn, then use Dragon 2's thrusters to place the vehicle into a slow penguin tumble, with the docking still secure.
5. Use an expendable Falcon Heavy to launch a stripped-down Dragon 2 directly into TLI. The stripped-down Dragon 2 has no aeroshell, no heat shield, no parachutes, no ballast sled, and only one SuperDraco in each engine pod. It also has fixed landing legs on the trunk, a propulsion pallet mated to the trunk payload adapter, and either suitports or an expandable airlock in place of its egress hatch. Keep the Falcon upper stage mated to the trunk.
6. Once the crewed Dragon 2 arrives at the moon, the Falcon 9 upper stage mated to its nose performs one additional burn for direct LLO insertion, then it is discarded.
7. Once the second stack arrives at the moon, its Falcon 9 upper stage is also used for the same lunar orbit insertion burn, but it remains mated to the trunk of the modified Dragon 2.
8. The crewed Dragon 2 executes a rendezvous with the second stack, docks nose-to-nose, and executes crew transfer. The first Dragon 2 then performs a deorbit burn with its propulsion assist pallet, undocks, and then reverses and brings its orbit back up.
9. The lander, with Falcon 9 upper stage still attached, descends toward the landing point. Shortly before periapse, the Falcon 9 upper stage fires to kill horizontal velocity, then is jettisoned. The lander descends on SuperDracos and lands.
10. Following the lunar surface mission, the SuperDracos fire again to lift off and raise apoapse, after which the propulsion assist pallet in the trunk is fired to burn into orbit. Once orbit is reached, the propulsion assist pallet is discarded, and the two Dragons rendezvous. Crew transfers back, and the first spacecraft burns for home.

[sevenperforce]

11 hours ago, cubinator said:

I can already tell...during final descent I'll be making one of these faces:

(Hint: it's either the one on the left or the one on the right.)

I'm not comfortable with the idea of flipping around while plummeting towards the ground inside a rocket, but pfft. It's only seven minutes of my life and anything that ends in me being on Mars is a win in my book.

It's a yaw motion, which shouldn't be too high on the gees. The higher-gee maneuver will be the stall swoop at the end.

10 hours ago, grungar3x7 said:

I mean that the spacecraft should be entering atmosphere inverted, nose down, like in the Adelaide presentation.

Right, that's what I meant too.

Split body flaps can only do you so far; at some point you need to have an entry profile which utilizes your a single fixed lifting surface. 

A nose-up entry would cause a "skip" and fail to complete entry at all; you'd lose speed while gaining altitude, both of which decrease available lift, and you'd eventually stall out at the edge of the atmosphere and fall into a tumble. This was the reason the Shuttle needed a very complex entry profile with big S-curves. Coming in nose-down directs that same lift vector roughly down and opposite your direction of flight, so you are pushed deeper into the atmosphere and lift remains constant.

The one thing I'm worried about here is the drag effects on those winglets. During the initial nose-down entry, those winglets are going to get a TON of drag, and it is REALLY going to want to go shuttlecock and roll 180 degrees. I don't know how they will prevent that.

Once you're through that portion, it gets much easier. The heavy nose and heavy engine cluster put the CoM very close to the physical center of the vehicle, allowing that scary-looking yaw flip on RCS. After you're through the majority of the heating, you can yaw around to nose-up, then pitch down and use body flaps to further adjust pitch to control your trajectory. Can't do that sooner, or you'd burn your nose off.

At this point, you're still coming in toward your landing site at hypersonic speeds. Retropropulsive braking would take way too much propellant at this point, so you use control surfaces to pitch up and climb, trading velocity for altitude slowly until you stall just above your landing site. RCS is used to prevent uncontrollable tumble, and the engines are lit for the landing burn.

I'm worried about post-stall stability, though.