Interstellar Travel in Gwynne Shotwell's Lifetime

[Oberonian]

https://twitter.com/thesheetztweetz/status/1187745445361180672

Shotwell: "I think we will have a propulsion breakthrough in my lifetime that we can then say we will build a ship and start the journey" to the next potentially habitable solar system.

What kind of technologies could Ms Shotwell be referring to? People who have done the hard math on the rocket equation, energy densities, and efficiencies have shown that a fission based nuclear engine can achieve up to 0.05c, fusion engines can achieve up to 0.1c, and antimatter engines could hit up to 0.9c. Unprecedented developments in reliability engineering are required for any of these propulsion schemes, and fission based rocketry doesn't strike me as providing interstellar voyages on a useful time scale. What could Gwynne have in mind?

How do we know Shotwell has said anything on those lines..as it is not her account ?

Because if she didnt, she could sue Michael Sheetz for false reporting.

Okay and Musk mentions the sun....as limited source of energy for it.

Do we have to guess further ?

[rakaydos]

https://twitter.com/thesheetztweetz/status/1187745445361180672

Shotwell: "I think we will have a propulsion breakthrough in my lifetime that we can then say we will build a ship and start the journey" to the next potentially habitable solar system.

What kind of technologies could Ms Shotwell be referring to? People who have done the hard math on the rocket equation, energy densities, and efficiencies have shown that a fission based nuclear engine can achieve up to 0.05c, fusion engines can achieve up to 0.1c, and antimatter engines could hit up to 0.9c. Unprecedented developments in reliability engineering are required for any of these propulsion schemes, and fission based rocketry doesn't strike me as providing interstellar voyages on a useful time scale. What could Gwynne have in mind?

How do we know Shotwell has said anything on those lines..as it is not her account ?

Because if she didnt, she could sue Michael Sheetz for false reporting.

Okay and Musk mentions the sun....as limited source of energy for it.

Do we have to guess further ?

You're welcome to not participate, if you dont think this topic is interesting.

[Robotbeat]

I have in mind extremely low TRL propulsion tech that would allow us to do human-lifetime interstellar missions. Not even a new idea and it satisfies the laws of physics just fine. But to actually demonstrate it would be a breakthrough.

I don’t know why people are so aghast that Shotwell said something like that.

[Frogstar_Robot]

I have in mind extremely low TRL propulsion tech that would allow us to do human-lifetime interstellar missions. Not even a new idea and it satisfies the laws of physics just fine. But to actually demonstrate it would be a breakthrough.

I don’t know why people are so aghast that Shotwell said something like that.

Because it is obviously an absurd suggestion. There is very little chance of a breakthrough that would theoretically enable interstellar travel, the magnitude of the problems are so big, let alone start building anything.

The only semi-realistic proposal now is Breakthrough Starshot, and that involves "spacecraft" of a few grams, and a humongous laser way bigger than anything evcer build and unlikely to get funding.

[rakaydos]

I have in mind extremely low TRL propulsion tech that would allow us to do human-lifetime interstellar missions. Not even a new idea and it satisfies the laws of physics just fine. But to actually demonstrate it would be a breakthrough.

I don’t know why people are so aghast that Shotwell said something like that.

Because it is obviously an absurd suggestion. There is very little chance of a breakthrough that would theoretically enable interstellar travel, the magnitude of the problems are so big, let alone start building anything.

The only semi-realistic proposal now is Breakthrough Starshot, and that involves "spacecraft" of a few grams, and a humongous laser way bigger than anything evcer build and unlikely to get funding.

But one breakthrough in laser focusing, and a SpaceX with a million person mars base and a full starlink network might think about privately funding that "humongous laser."

Or if the breakthrough is in another area, like van allen belt positron capture, they might go for a different design.

[Robotbeat]

I have in mind extremely low TRL propulsion tech that would allow us to do human-lifetime interstellar missions. Not even a new idea and it satisfies the laws of physics just fine. But to actually demonstrate it would be a breakthrough.

I don’t know why people are so aghast that Shotwell said something like that.

Because it is obviously an absurd suggestion. There is very little chance of a breakthrough that would theoretically enable interstellar travel, the magnitude of the problems are so big, let alone start building anything....

LOL, no, sorry. The fact that your imagination is too small for it doesn't make it absurd. And you're not qualified to guess the chance of a breakthrough in the next century, anyway. Shotwell is far better qualified.

The method I have in mind that would enable interstellar travel (potentially for humans in a human lifespan) would require a beaming structure at least 1000km in length and at least 1 million tons in mass. This sounds absurd WITHOUT Starship.

We're talking about a company that is building the launch infrastructure to support a million person city on Mars. This would mean tens of millions of tons IMLEO, most likely.

With 2 Starships built a week, 100 a year, and each used 100 times on average (or, say, 150 times plus every 10 Starships is a booster which is reused 1000 times), with at least 100 tons capacity apiece, that's a steady state of about 1 million tons to orbit per year. (And that's just to start. If you increase to 18m Starships, increase capacity to about 500 tons, do about 2000 reuses, that increases to 10 million tons per year IMLEO... Musk has talked about 100 million tons per year in the very, very long-term.)

A million ton structure seems relatively mundate with the capability I describe above.

1 million tons devoted to solar power at 10,000W/kg would enable 10 Trillion watts.

Or maybe more realistically 10 million tons with 1000W/kg solar (something with this specific power already flew as part of the IKAROS solar sail, which included very high specific power thin film solar cells) to get 10TW, if you prefer. Starship makes either one feasible.

10TW of solar powering a linear accelerator assembled in space can beam macrons to a magsail-equipped craft (which would need to have a device that vaporizes the incoming macrons to a plasma), which would sail on a sort of artificial near-relativistic artificial stellar wind. A larger magsail would slow down (against the interstellar plasma). Likely some sort of extended sleep, hibernation, torpor (NASA had a NIAC study on this), etc, to enable the crew to handle such long periods in a small spacecraft. None violates the laws of physics. All requires significant technological advancement.

SpaceX, including Shotwell, are operating at a scale beyond the comprehension of many folk. And she has the accomplishments to be able to do so.

Sorry you're not able to think from first principles. That's a tough life for a space enthusiast.

[Robotbeat]

The audacity of someone like Frog who has almost no knowledge of actual interstellar propulsion concepts (besides a brief mention of Project Starshot) scolding Gwynne Shotwell, the frakking President of SpaceX, for being “absurd” for suggesting interstellar propulsion could be feasible... is pretty impressive. Gotta have pretty big cajones to walk into a conversation you know nothing about and scold the most successful woman in the aerospace world for being “absurd” LOL

Doesn’t your signature say something about being civil and respectful?

[Oberonian]

https://twitter.com/thesheetztweetz/status/1187745445361180672

Shotwell: "I think we will have a propulsion breakthrough in my lifetime that we can then say we will build a ship and start the journey" to the next potentially habitable solar system.

What kind of technologies could Ms Shotwell be referring to? People who have done the hard math on the rocket equation, energy densities, and efficiencies have shown that a fission based nuclear engine can achieve up to 0.05c, fusion engines can achieve up to 0.1c, and antimatter engines could hit up to 0.9c. Unprecedented developments in reliability engineering are required for any of these propulsion schemes, and fission based rocketry doesn't strike me as providing interstellar voyages on a useful time scale. What could Gwynne have in mind?

How do we know Shotwell has said anything on those lines..as it is not her account ?

Because if she didnt, she could sue Michael Sheetz for false reporting.

Okay and Musk mentions the sun....as limited source of energy for it.

Do we have to guess further ?

You're welcome to not participate, if you dont think this topic is interesting.

Aaah sorry I mean unlimited source...my bad.

[joek]

Because it is obviously an absurd suggestion. There is very little chance of a breakthrough that would theoretically enable interstellar travel, the magnitude of the problems are so big, let alone start building anything.

The only semi-realistic proposal now is Breakthrough Starshot, and that involves "spacecraft" of a few grams, and a humongous laser way bigger than anything evcer build and unlikely to get funding.

Shotwell stated (emphasis added): "I think we will have a propulsion breakthrough in my lifetime that we can then say we will build a ship and start the journey"  Think you may be reading more into that statement than warranted.  Nothing she said is at odds with Starshot, or other potential-emerging technologies and capabilities.

[Oberonian]

Could SpaceX go nuclear ? 

[Robotbeat]

Could SpaceX go nuclear ? 

Sure, but it's best to think in the context of what a megaton to orbit per year enables, as well as regular mass travel between Earth and Mars.

Fusion, fission, some sort of beamed propulsion, etc. This stuff requires humanity to be operating at a scale in orbit unlike anything we've done so far. But if we ARE interplanetary, with a megaton of trade going on, perhaps we'll have the ingredients from which interstellar travel will grow.

[Vultur]

Could SpaceX go nuclear ? 

Even besides political/regulatory issues, existing or near-term nuclear technology (e.g. NERVA) isn't really useful for interstellar.

There are fusion concepts that might work (e.g. Project Daedalus and its successors) but that's way beyond near-term.

Beamed power to sails might be more likely. I do have to wonder about something like Breakthrough Starshot hitting interstellar dust though... 20% of lightspeed is a lot of kinetic energy.

But there's not much point in interstellar until the Solar System is pretty thoroughly industrialized. If there are terawatts or petawatts or more of solar power production capacity in space, lots of things become possible...

 

Shotwell stated (emphasis added): "I think we will have a propulsion breakthrough in my lifetime that we can then say we will build a ship and start the journey"  Think you may be reading more into that statement than warranted.

I agree. That might just mean "we will be in a position to make real plans for interstellar travel" - 'we can then say we will build a ship' not 'it will already be built and launched'.

With sufficiently optimistic assumptions about the pace of industrialization of the solar system once Starship is flying, that might be the case in 50 years.

[Alberto-Girardi]

Could SpaceX go nuclear ? 

Even besides political/regulatory issues, existing or near-term nuclear technology (e.g. NERVA) isn't really useful for interstellar.


But there's not much point in interstellar until the Solar System is pretty thoroughly industrialized. If there are terawatts or petawatts or more of solar power production capacity in space, lots of things become possible...

I agree, but I think we need to try to send a probe to other solar systems as soon as  possible, to inspire people (is exactly the idea behind starshot). IIUC the most near term technology light/solar sails, but allows only small probes and can't support crewed mission (excluding enourmous infrastructures).
 
I hope that what Shotwell says happen, but in 40 years (she is 57, I hope she lives long) I'm not super sure if it will happen. In the '60 there were great plans, and never realized. Now, with advanced technology we (as humanity) have to exploit the "momentum" that there is now due to SpaceX, Artemis program, new companies etc. to make what Shotwell said possible.

[rakaydos]

Could SpaceX go nuclear ? 

Fission is probably too regulated (and for good reason) on earth, but if fusion starts to take off in the next few years, or there's an antiproton capture breakthrough, or if the mars base finds a good stockpile of thorium...

[Robotbeat]

Could SpaceX go nuclear ? 

Fission is probably too regulated (and for good reason) on earth, but if fusion starts to take off in the next few years, or there's an antiproton capture breakthrough, or if the mars base finds a good stockpile of thorium...

Fission is feasible to do even with all the regulations if SpaceX had a really, really good reason for it. But nuclear doesn't trade as well as you might think vs chemical & solar (for ISRU).

For interstellar? sure.

[Oberonian]

How many means of propulsion do we have that takes us to Proxima Centauri and back in a decent time frame ?


Will the astronauts become younger ( according to Einstein ) and if so how much ?


I think my idea of fast moving space station ( between the Sun and Jupiter ) as a launch pad might work with ION drive.

Any others ?

[Frogstar_Robot]

How many means of propulsion do we have that takes us to Proxima Centauri and back in a decent time frame ?

None. I am assuming "decent" means within a human lifetime.

Bear in mind we aren't even an interplanetary species yet. We might achieve that in the next 30 years. Going interstellar is orders of magnitude different. We don't need just one breakthrough, we need dozens. Don't expect the colony ship leaving for Homeland in the next 100 years, at least.

Will the astronauts become younger ( according to Einstein ) and if so how much ?

I wondered about that, turns out there are plenty of online calculators https://calculators.io/time-dilation/. Unless you are going a lot more than 1% c, it doesn't make much difference.

I think my idea of fast moving space station ( between the Sun and Jupiter ) as a launch pad might work with ION drive.

I don't see how that helps.

Any others ?

[Oberonian]

How many means of propulsion do we have that takes us to Proxima Centauri and back in a decent time frame ?

None. I am assuming "decent" means within a human lifetime.

Bear in mind we aren't even an interplanetary species yet. We might achieve that in the next 30 years. Going interstellar is orders of magnitude different. We don't need just one breakthrough, we need dozens. Don't expect the colony ship leaving for Homeland in the next 100 years, at least.

Will the astronauts become younger ( according to Einstein ) and if so how much ?

I wondered about that, turns out there are plenty of online calculators https://calculators.io/time-dilation/. Unless you are going a lot more than 1% c, it doesn't make much difference.

I think my idea of fast moving space station ( between the Sun and Jupiter ) as a launch pad might work with ION drive.

I don't see how that helps.

Any others ?

Cool...fast trip to Proxima @ 0.4 C...12 years and you yourself seem only 11 years older.

[Alberto-Girardi]

Will the astronauts become younger ( according to Einstein ) and if so how much ?

No, time can't be reverted. Astronauts travelling at high speed will be younger than people that had thei same age at the start, becuse the times passes slowerly  fo higher speeds

[RotoSequence]

Will the astronauts become younger ( according to Einstein ) and if so how much ?

No, time can't be reverted. Astronauts travelling at high speed will be younger than people that had thei same age at the start, becuse the times passes slowerly  fo higher speeds

Negative mass and negative energy density would permit this, but those are particularly un-physical states of matter.