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There are many small orbital launch vehicles proposed or under development

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Re: There are many small orbital launch vehicles proposed or under development

#21

Post by marcosdumay »

prestonh wrote: post #18
jdsully wrote: post #9

Earlier quoted context omitted.

Low earth orbit satellites decay very quickly. Without extra boost most satellites launched by these rockets will reenter within a year or two. On a wider note, I find the dramatic pessimism of our times rather unfortunate. It seems every technical advance is now met with some prediction of doom. I miss when technical forums were optimistic.

I havent researched the orbital dynamics much here, but wouldnt it be possible for the satellite fragments resulting from a collision at orbital speeds to have much greater speeds, possibly ending up in elliptical orbits with lower total drag? Seems like just waiting for orbits to decay after a Kessler syndrome like event wouldnt be feasible.

Yes, it is possible. If you get an explosion, many fragments will be in an elliptical orbit where they can stay longer than on LEO. But there is a trade-off here, the time during what a fragment is dangerous is exactly the same time it is in a high drag region, so if it's not feasible to wait for it to fall down, it is also not really dangerous either.

Re: There are many small orbital launch vehicles proposed or under development

#23

Post by elil17 »

DuskStar wrote: post #16
Narkov wrote: post #15

Earlier quoted context omitted.

> They can't all win - and that's assuming any of them win. While I agree with your general point, do we completely understand the opportunity that space launch/travel/exploration provides yet? The opportunity may be exponentially bigger than we currently understand.

But smallsat launchers only make sense if they have a lower cost/kg (unlikely vs the F9) or if they're being used for an orbit/launch time that doesn't have enough demand for a rideshare. And if the space launch market gets big enough to support 100 smallsat launchers, a F9 rideshare into that special orbit will probably have enough takers to make it cheaper than the smallsat launcher would have.

Smaller diameter rockets have a much worse fuel ratio (because of fuel tank geometry issues), so there’s no way they’ll ever be cheaper than larger rockets. They fundamentally must use more fuel per kg of payload than large rockets because fuel tank wet mass to dry mass ratio increases linearly with diameter.

Re: There are many small orbital launch vehicles proposed or under development

#24

Post by DuskStar »

elil17 wrote: post #23
DuskStar wrote: post #16

Earlier quoted context omitted.

But smallsat launchers only make sense if they have a lower cost/kg (unlikely vs the F9) or if they're being used for an orbit/launch time that doesn't have enough demand for a rideshare. And if the space launch market gets big enough to support 100 smallsat launchers, a F9 rideshare into that special orbit will probably have enough takers to make it cheaper than the smallsat launcher would have.

Smaller diameter rockets have a much worse fuel ratio (because of fuel tank geometry issues), so there’s no way they’ll ever be cheaper than larger rockets. They fundamentally must use more fuel per kg of payload than large rockets because fuel tank wet mass to dry mass ratio increases linearly with diameter.

Right, and that's why smallsat launchers are only really viable for orbits/launches that can't be served by rideshares. Better to pay $5mil for an Electron to launch your smallsat than to book an entire Falcon 9, even if the $/kg is far higher.

Re: There are many small orbital launch vehicles proposed or under development

#25

Post by greglindahl »

DuskStar wrote: post #24
elil17 wrote: post #23

Earlier quoted context omitted.

Smaller diameter rockets have a much worse fuel ratio (because of fuel tank geometry issues), so there’s no way they’ll ever be cheaper than larger rockets. They fundamentally must use more fuel per kg of payload than large rockets because fuel tank wet mass to dry mass ratio increases linearly with diameter.

Right, and that's why smallsat launchers are only really viable for orbits/launches that can't be served by rideshares. Better to pay $5mil for an Electron to launch your smallsat than to book an entire Falcon 9, even if the $/kg is far higher.

Companies like Momentus [1] are happy to sell you a tug that will turn a rideshare to a common orbit into your unusual orbit.

SpaceX's rate for an Electron-sized payload is 1/6 the price of an Electron.

1: https://momentus.space/

Re: There are many small orbital launch vehicles proposed or under development

#26

Post by Robotbeat »

trianglem wrote: post #22

This sounds like it may or may not be true. Is this all because of Elon Musk?

Not an insignificant part of it IS because of Elon Musk. SpaceX has been crazily successful, AND it has a high churn rate, so the know-how gets spread throughout the industry in startups like these. The latter may be bad for SpaceX (arguable?), but I think it's good for the industry.

Re: There are many small orbital launch vehicles proposed or under development

#28

Post by adventured »

DuskStar wrote: post #8
mrfusion wrote: post #3

Could we be at the very beginning of a Cambrian explosion for space exploration? Exciting times.

Either that or the beginning of a new dot-com bubble. Most of those smallsat companies are financially viable on the expectation that they capture a meaningful fraction of the smallsat market - like 1/5th or more. They can't all win - and that's assuming any of them win. SpaceX seems to be planning to own the rideshare market [0], and so unless a customer really cares about having a particular orbit that's going to b…

> Either that or the beginning of a new dot-com bubble.

The dotcom bubble was the start of a cambrian explosion.

Those two events are part of the same process, not wholly separate entities in which case one is bad and the other is good. They require eachother and cannot be unlinked. The dotcom bubble was not a bad thing, it was a necessary process of chaotic, sometimes idiotic, experimentation. It was an extraordinary good. The total sum of all capital destroyed during the dotcom bubble (which lasted less than four years) would fit into a corner of Amazon's present market value.

Unless you want to pretend that humans are all-knowing gods. In which case we require no experimentation, there are no foolish mistakes possible, no errors of judgment possible, no irrationalism or over-excitement is possible, no emotion is possible, no idiots and malevolent actors (eg con-artists) are possible. And so on.

We should all be hopeful - giddy in fact - if we're about to see a space-focused dotcom style bubble. Bring on the space bubble, do it right now, let's get moving with that. That will be truly extraordinary, it will signal what comes after: a real, massive, sustainable expansion.

The global Internet is beyond a magnitude more valuable - in every way you can measure it, whether in business transacted, value of tech companies, or how valuable it is to end users - today than it was at the peak of the dotcom bubble in 2000.

Re: There are many small orbital launch vehicles proposed or under development

#29

Post by DuskStar »

greglindahl wrote: post #25
DuskStar wrote: post #24

Earlier quoted context omitted.

Right, and that's why smallsat launchers are only really viable for orbits/launches that can't be served by rideshares. Better to pay $5mil for an Electron to launch your smallsat than to book an entire Falcon 9, even if the $/kg is far higher.

Companies like Momentus [1] are happy to sell you a tug that will turn a rideshare to a common orbit into your unusual orbit. SpaceX's rate for an Electron-sized payload is 1/6 the price of an Electron. 1: https://momentus.space/

I have to say, 5 km/s delta v is more than I was expecting from a tug like that. Still, I really wouldn't be surprised if adding one of those to your smallsat would cost more than $5m.

Re: There are many small orbital launch vehicles proposed or under development

#30

Post by Rebelgecko »

remarkEon wrote: post #17
saagarjha wrote: post #13

Earlier quoted context omitted.

While this is technically true for all satellites, what's important is the timescale on which their orbits will decay.

What is the distribution of the time scale of these orbits though? If 90% of these things take a couple months (or weeks or days or whatever) to decay and burn up it seems like a non-issue - or one that can be planned around. If the fat tail sits further out in time that seems like it could actually become an issue.

One of the junkiest places in orbit right now is around 800-1000km (mostly thanks to the Chinese ASAT weapon test 12 years ago and an unrelated collision between two satellites in 2009. There's also tens thousands of droplets of irradiated coolant that was ejected from Soviet nuclear reactors in 70s-80s). At 1000km it can take around 100 years for something to deorbit from drag (can vary a bit depending on unpredictable space weather events).

1000km is still in Low Earth Orbit, but lower parts of LEO decay more quickly, e.g. months years or decades depending on the orbit's height.

When you get into orbits higher than LEO (MEO: medium Earth orbit, GEO), the timescales before something reenters can get more geological. A GPS satellite (~20,000km up, near the middle of MEO) left to its own devices will stay up for hundreds of thousands, if not millions of years.

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