Author Topic: P2P Without Super Heavy  (Read 4071 times)

Offline raketa

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P2P Without Super Heavy
« on: 03/21/2019 12:19 am »
Could P2P be achieve without Starship only.
SH + SS:
1/ has capacity to deliver 1000 people, it is too much
2/It is to noisy, Starship could launch closer to shore
3/If 100 people could travel, it is 10-15 ton "cargo" weight
4/Fuel price $250,000 -> 2,500/person

Re: P2P Without Super Heavy
« Reply #1 on: 03/21/2019 09:57 pm »
How is 1000 people too much?

If it could actually fit that man I'd say fantastic. Really lowers the cost per person and gets a lot of people somewhere very quickly. When you think that each origin point will probably only have one flight in per day from it to somewhere... I don't see the problem if the ship is big enough.

Couldn't they scale down the booster for P2P?

Their biggest problem will be regulatory. You know the airlines are going to freak when the system comes on line.

Offline Stan-1967

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Re: P2P Without Super Heavy
« Reply #2 on: 03/21/2019 10:08 pm »
I think insurance my be a bigger problem vs. regulatory or max payload.  Who will insure this venture  before a reliable history is known?  Will SpaceX self insure?   Think of what it costs to kill a passenger manifest of 100 multimillionaires vs. 1000.  Millionaires are the target market here, and for the time saving, tickets will be comparable to first class fares, so probably in the range of $5000-$10000 plus each way.

Offline Tulse

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Re: P2P Without Super Heavy
« Reply #3 on: 03/22/2019 02:19 pm »
How is 1000 people too much?
The demand likely isn't there.  The largest plane currently in production, the A380 with a capacity of of 500 to 850 passengers, was just cancelled because no airliner could find a profitable market for it.

Also, because SS travels so quickly, even if there is a large demand, it could be met by multiple flights per day, something that much slower planes couldn't match.  If anything, SS could be scaled for much smaller passenger capacity than long-haul airliners and still meet demand, because it can make many more flights for a given amount of time.

Offline RonM

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Re: P2P Without Super Heavy
« Reply #4 on: 03/22/2019 03:48 pm »
How is 1000 people too much?
The demand likely isn't there.  The largest plane currently in production, the A380 with a capacity of of 500 to 850 passengers, was just cancelled because no airliner could find a profitable market for it.

Also, because SS travels so quickly, even if there is a large demand, it could be met by multiple flights per day, something that much slower planes couldn't match.  If anything, SS could be scaled for much smaller passenger capacity than long-haul airliners and still meet demand, because it can make many more flights for a given amount of time.

With a suborbital flight path and only 100 or so passengers, a version of Starship could be designed to do P2P without Super Heavy.

Offline Tulse

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Re: P2P Without Super Heavy
« Reply #5 on: 03/22/2019 06:33 pm »
With a suborbital flight path and only 100 or so passengers, a version of Starship could be designed to do P2P without Super Heavy.
I agree, although I have never been clear on how much P2P is supposed to be a separate endeavour, versus just using the ships SpaceX is making for other purposes and refitting the interior for short passenger travel.  That is, I don't know if SpaceX would design a ship just for P2P.

Offline Jim

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Re: P2P Without Super Heavy
« Reply #6 on: 03/22/2019 06:47 pm »
because it can make many more flights for a given amount of time.

based on what data?

Offline Tulse

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Re: P2P Without Super Heavy
« Reply #7 on: 03/22/2019 07:15 pm »
because it can make many more flights for a given amount of time.

based on what data?
Granted that's presuming that a ship works like an airliner and doesn't require lengthy refurbishment between flights.  But given that it can do routes that take planes 12 hours in about 30 minutes, there is lots of time there to do multiple trips, again presuming that the ship itself is gas 'n' go.

Online guckyfan

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Re: P2P Without Super Heavy
« Reply #8 on: 03/22/2019 07:17 pm »
With a suborbital flight path and only 100 or so passengers, a version of Starship could be designed to do P2P without Super Heavy.
I agree, although I have never been clear on how much P2P is supposed to be a separate endeavour, versus just using the ships SpaceX is making for other purposes and refitting the interior for short passenger travel.  That is, I don't know if SpaceX would design a ship just for P2P.

It would not be a too big redesign. I had thought about this possibility. Move the bulkheads to accomodate more propellant. The engines have enough thrust to lift a few hundred more tons of propellant. For 100 passengers there is enough space in the conical part of Starship. 100 passengers is what Gwynne Shotwell mentioned.


Offline speedevil

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Re: P2P Without Super Heavy
« Reply #9 on: 03/22/2019 07:26 pm »
It would not be a too big redesign. I had thought about this possibility. Move the bulkheads to accomodate more propellant. The engines have enough thrust to lift a few hundred more tons of propellant. For 100 passengers there is enough space in the conical part of Starship. 100 passengers is what Gwynne Shotwell mentioned.

Was there a more recent statement than the 'cheaper than an economy ticket at IAC2017?' - because that pretty much implies 1000ish passengers long-haul(with $300K ship amortisation, 300K launch costs 300K sundry and profit).

Going to 100 passengers means that you either jack the price up a _lot_ or your vehicle is an order of magnitude cheaper to launch (100K per launch total), which seems challenging.

Online guckyfan

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Re: P2P Without Super Heavy
« Reply #10 on: 03/22/2019 07:52 pm »
Was there a more recent statement than the 'cheaper than an economy ticket at IAC2017?' - because that pretty much implies 1000ish passengers long-haul(with $300K ship amortisation, 300K launch costs 300K sundry and profit).

Going to 100 passengers means that you either jack the price up a _lot_ or your vehicle is an order of magnitude cheaper to launch (100K per launch total), which seems challenging.

It was cheaper than business class, undiscounted. Flying Starship only without the booster should drastically reduce cost. Only ~20% of the propellant, no stacking, only 7 engines instead of 39.

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Re: P2P Without Super Heavy
« Reply #11 on: 03/22/2019 08:17 pm »
Could P2P be achieve without Starship only.
SH + SS:
1/ has capacity to deliver 1000 people, it is too much
2/It is to noisy, Starship could launch closer to shore
3/If 100 people could travel, it is 10-15 ton "cargo" weight
4/Fuel price $250,000 -> 2,500/person

1. The A380 proves that there's no competitive market for an airplane with >500 passengers. A rocket has a different cost model though, so analogies are necessarily imperfect. The economically optimal size for a rocket is not necessarily the same as an airplane. A single Super Heavy Starship can serve a half dozen antipodal city pairs at one flight per day, whereas an A380 would require one vehicle per city pair. And unlike airplanes, the per-km fuel cost decreases with distance, so we might see the market carved up that way. Fundamentally the two cost landscapes are very different.

2. Is the noise limit defined by the roar from launch, or the boom from reentry? At the Falcon Heavy launch the sonic boom was much louder and more disruptive than the rumble of launch. If it's really a problem than super-sized rainbirds (stormbirds?) placed in a semi-circle around the pad can shoot seawater in the air to absorb/deflect sound away from the city. Super Heavy should have a similar loudness boom as Starship.

Also, what's so costly about being farther from shore? The fast ferry and/or helicopter ride may be slightly longer, but that's cheap (and the travel time still beats the pants off an airplane). Any person/cargo that needs "as fast as possible" service has no faster alternative, so the only demand reduction would come from losing time-critical payload that's right on the line re:urgency, such that the small increase in trip time crosses the threshold and makes airplanes more economical. This is likely imo to be a small segment of the P2P payload market, which will be well saturated by some combination of "poor man's space tourism" back in Econony and wealthy-or-not conspicuous consumers Instagramming from the First Class seats. Neither market is time-critical to that degree.

3. The payload to fuel ratio is vastly better for Super Heavy Starship vs Starship. Elon Musk described SSTO as "pointless:"
https://twitter.com/elonmusk/status/1076613555091234816

Notice he didn't say "impossible;" his point is that it's economically undesirable, not that it's technically infeasible. Nothing has changed that conclusion imo.

4. Do we know that SSTO Starship can carry 100 people? I know there have been improvements recently, but last I knew we weren't even sure if it SSTO Starship could carry landing fuel. That's a long way from carrying any payload at all, and even further from being economically competitive with Super Heavy Starship.

Some might suggest that the recent technical advances make SSTO more feasible/affordable. Maybe so, but I've never yet seen SpaceX use good engineering/cost decisions to "buy" bad decisions elsewhere. SSTO needs to stand on its own technical/economic merits, and I don't see that.

Online Slarty1080

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Re: P2P Without Super Heavy
« Reply #12 on: 03/22/2019 08:58 pm »
Could P2P be achieve without Starship only.
SH + SS:
1/ has capacity to deliver 1000 people, it is too much
2/It is to noisy, Starship could launch closer to shore
3/If 100 people could travel, it is 10-15 ton "cargo" weight
4/Fuel price $250,000 -> 2,500/person

1. The A380 proves that there's no competitive market for an airplane with >500 passengers. A rocket has a different cost model though, so analogies are necessarily imperfect. The economically optimal size for a rocket is not necessarily the same as an airplane. A single Super Heavy Starship can serve a half dozen antipodal city pairs at one flight per day, whereas an A380 would require one vehicle per city pair. And unlike airplanes, the per-km fuel cost decreases with distance, so we might see the market carved up that way. Fundamentally the two cost landscapes are very different.

2. Is the noise limit defined by the roar from launch, or the boom from reentry? At the Falcon Heavy launch the sonic boom was much louder and more disruptive than the rumble of launch. If it's really a problem than super-sized rainbirds (stormbirds?) placed in a semi-circle around the pad can shoot seawater in the air to absorb/deflect sound away from the city. Super Heavy should have a similar loudness boom as Starship.

Also, what's so costly about being farther from shore? The fast ferry and/or helicopter ride may be slightly longer, but that's cheap (and the travel time still beats the pants off an airplane). Any person/cargo that needs "as fast as possible" service has no faster alternative, so the only demand reduction would come from losing time-critical payload that's right on the line re:urgency, such that the small increase in trip time crosses the threshold and makes airplanes more economical. This is likely imo to be a small segment of the P2P payload market, which will be well saturated by some combination of "poor man's space tourism" back in Econony and wealthy-or-not conspicuous consumers Instagramming from the First Class seats. Neither market is time-critical to that degree.

3. The payload to fuel ratio is vastly better for Super Heavy Starship vs Starship. Elon Musk described SSTO as "pointless:"
https://twitter.com/elonmusk/status/1076613555091234816

Notice he didn't say "impossible;" his point is that it's economically undesirable, not that it's technically infeasible. Nothing has changed that conclusion imo.

4. Do we know that SSTO Starship can carry 100 people? I know there have been improvements recently, but last I knew we weren't even sure if it SSTO Starship could carry landing fuel. That's a long way from carrying any payload at all, and even further from being economically competitive with Super Heavy Starship.

Some might suggest that the recent technical advances make SSTO more feasible/affordable. Maybe so, but I've never yet seen SpaceX use good engineering/cost decisions to "buy" bad decisions elsewhere. SSTO needs to stand on its own technical/economic merits, and I don't see that.

That is a good point. Although there should be room for 100 people, there might not be enough mass lift capacity from SS alone. On the positive side the flight would at maximum “only” traverse halfway around the planet and possibly much less, so there should be saving in propellant compared to an orbital flight. Hard to say how this calculation would balance out, but a great distance could certainly be covered. The exact extent of that distance is hard to say.
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Offline RonM

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Re: P2P Without Super Heavy
« Reply #13 on: 03/22/2019 10:03 pm »
Who says it needs to be SSTO? We're talking about P2P trajectories. No need for a P2P craft to reach LEO.

Offline speedevil

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Re: P2P Without Super Heavy
« Reply #14 on: 03/22/2019 11:08 pm »
Who says it needs to be SSTO? We're talking about P2P trajectories. No need for a P2P craft to reach LEO.

It damn near does.
If you're doing more than very short suborbital hops, you can't loft the trajectory much or you end up entering at too steep an angle, an at least having unpassenger G levels.
Correcting the entry angle propulsively leads you closer to SSTO requirements with the added delta-v.

Offline livingjw

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Re: P2P Without Super Heavy
« Reply #15 on: 03/23/2019 12:08 am »
Ballistically going halfway around the earth takes nearly the same delta V as going to orbit. For example, the shuttle external tank is a few hundred feet per second below orbital speed but reenters in the Indian Ocean.

Offline RonM

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Re: P2P Without Super Heavy
« Reply #16 on: 03/23/2019 12:57 am »
Okay, tougher than I thought.

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Re: P2P Without Super Heavy
« Reply #17 on: 03/23/2019 01:19 am »
because it can make many more flights for a given amount of time.

based on what data?

Based on Gwynne Shotwell's statements at TED. She specifically noted multiple long-haul flights/day vs the 1-2 an airliner could do as a financial driver.
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Offline cuddihy

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Re: P2P Without Super Heavy
« Reply #18 on: 03/23/2019 04:13 am »
because it can make many more flights for a given amount of time.

based on what data?

Based on Gwynne Shotwell's statements at TED. She specifically noted multiple long-haul flights/day vs the 1-2 an airliner could do as a financial driver.

And how many design iterations are needed before you can land a superheavy back on its launch mount + connect up GSE; land starship, empty it, move it back to the pad, crane the multi hundred ton starship smoothly (eg stage integrate) back on top of it, + reload passengers, all in a few hours?

Let’s be real, we’re actually talking a very different system at that point, not even sure you can call that Starship / Superheavy.

* edit: when did ampersand in the body of the text start putting out “amp”, &
« Last Edit: 03/23/2019 04:33 am by cuddihy »

Online docmordrid

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Re: P2P Without Super Heavy
« Reply #19 on: 03/23/2019 04:23 am »
because it can make many more flights for a given amount of time.

based on what data?

Based on Gwynne Shotwell's statements at TED. She specifically noted multiple long-haul flights/day vs the 1-2 an airliner could do as a financial driver.

And how many design iterations are needed before you can land a superheavy back on its launch mount & connect up GSE; land starship, empty it, move it back to the pad, crane the multi hundred ton starship smoothly (eg stage integrate) back on top of it, & reload passengers, all in a few hours?

Let’s be real, we’re actually talking a very different system at that point, not even sure you can call that Starship / Superheavy.
Musk has said SH will use ?landing legs & fins like Starship, at least early on.

If you have an SH variant akin to a stretched StarHopper mini-booster which can be craned into position & stacked  after a flat-pad landing, P2P should be able hto fly earlier.



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