Size and albedo of the largest detected Oort-cloud object
arxiv.org
arxiv.org
A long-period comet, like an Oort cloud object, might impact at 50 km/s, instead of the 10-20 km/s of a near-Earth asteroid.
The physics might say that the energy might not be enough to literally vaporize the oceans or "sterilize" the biosphere, but the global ecosystem is fragile. This thing dropping on the planet would absolutely cause a mass extinction.
https://iopscience.iop.org/article/10.3847/psj/ac66e8
(extrapolated > 700 km impactor needed for sterilization)
However, (and here I speak from reading many other sources on this subject), even something the size of that latter object (basically something the size of a planet like Pluto) might not be enough.
Other studies have indicated that it might be exceptionally hard for heat to transfer enough through the vast mass of the earth's upper mantle and crust to actually melt it uniformly even if hit by something like the object that may have formed the moon.
This impactor was also supposed to be roughly 2,500km across and some of the theoretical concepts around it argue that even in that absolutely cataclysmic scenario, at least a part of the crust remains intact and relatively cool below a depth of several hundred meters.
If such a thing were to be true in the context of modern earth, which teems with life in every single possible remotely habitable nook and cranny and crevasse, then even a colossal impact by a 2,700km planet-type object wouldn't sterilize the Earth of life.
If only part of the crust remained intact as described above, then after hundreds of thousands or a few million years, as the earth's partially molten surface cools, and an atmosphere reforms, water that also reforms from vapor would rain down to the surface again in a vast global storm like something out of the bible. As this happens and the oceans refill, the tiny organisms concealed during all that time inside the deep cracks hundreds of meters below the surface of that surviving part of our world's crust would then recolonize the surface eventually and cause life to flourish again.
The key things in this scenario are that for one, at least one small part of the crust remains intact and cool, at least below a certain depth, and secondly, that water vapor eventually re-condenses into rain.
One might think that water would be vaporized right into separation of its hydrogen and oxygen atoms by the heat of such impacts, but mostly no. For that to happen the water on Earth would need to be subjected to at least something like 3,000 degrees Celsius of sustained heat, and even a planet-sized impact wouldn't generate such temperatures over most of the world.
Anyhow, sparked me into really thinking about all this again and the link you added was wonderful for that.
https://impacts.to/downloads/lowres/impacts.pdf#page=21
Sources: https://impacts.to/bibliography.pdf (search for K-Pg)
Imply that the kinetic energy released upon the impact of such an object, show a group sheltering at the ISS (orbit at an altitude of between 370–460 km (200–250 nmi)) or the Tiangong (orbit between 340 and 450 km (210 and 280 mi) ) would not be likely to survive the impact from ejecta thrown into their orbital altitude...
https://www.calculatorsoup.com/calculators/physics/kinetic.p...
Let's go with 1.0E+16 Kg for mass and 25000 m/s for impact speed what gives about KE = 3.125E+24 J
Assume 10% of that goes into ejecta.Then use the formula for Velocity from Kinetic Energy.
https://calculator.academy/kinetic-energy-to-velocity-calcul...
What gives about 8000 m/s of initial speed.
Follow that using Maximum Height Formula from kinematics based on a Gravitational acceleration at g: 9.8 m/s²
https://www.omnicalculator.com/physics/maximum-height-projec...
We are looking at eject reaching orbits of 2500 Km to 3000 Km above Earth. Heat and corresponding vaporization effects excluded for simplification purposes.
Now we wait for an event to validate my calculations....
I don't know the exact numbers, but for water ice the "frost line" is at about 3 au (between Mars and Jupiter)[0]—the line inside which icy comets and ice moons, like Europa, can't form. Presumably there's analogous zones for the increasingly volatile cryogenic ices, going out into the most distant regions—a solid carbon dioxide line, a carbon monoxide line, a cyanide line... The surface of Pluto, for example, is mostly solid nitrogen, with parts of solid methane and solid carbon monoxide [1].
The government would save billions (tens of billions over the long haul), increase cadence, increase mission scope, and cut flight times, by cutting NASA’s build-&-burn rocket manned program in favor of SpaceX’s reusable manned craft and space refueling services.
SpaceX Starship could also reduce the cost and increase cadence of scientific missions, in two ways:
1) By reducing launch costs via greater system reuse.
2) And by increasing available launch volume, eliminate a lot of the design & manufacturing time, cost, complexity and risk created by today’s need to fit craft into toad’s more limited volumes.
Less need for craft miniaturization means (a) fewer risky/complex unfolding maneuvers in flight, (b) much easier radiation mitigation via more shielding, larger more resilient circuits, redundancy, etc. And (c) fewer craft, with more capabilities and higher longevity.
And as with the manned program, increase mission scope, while reducing transfer to target times, via in orbit refueling.
If only we could find someone with the incentives, plan, means and mandate, to cut government space spending while somehow also expanding its manned & scientific space exploration capabilities and scope.
The hardest part is to find such a uniquely capable person, who also has enough slack time to take this on. A rare trait combination, indeed. What are the chances of finding a genius reefer doom scrolling bloviating slacker? Who could put all that disposable time to better use?
1) I think NASA does best when it focuses on the frontier of space, where private industry does not yet have the incentives or capabilities to increase our knowledge and access to space and solar system resources.
2) I think NASA does best, when it takes the greatest advantage of private industry, where ever industry is able to provide lower costs or higher performance.
I think this is more in line with how public money should be spent.
I think it reduces a lot of wasted money spent on unnecessary redundant and obsolete efforts.
I think it results in the greatest bang for the buck, for the government, and the greatest incentive to improve for industry.
At this time, I think the frontier NASA should be focused on (where industry is not yet incentivized enough), is manned space habitats, and unmanned and manned exploration of the solar system's potential manned sites and resources.
Where I think it should have already passed on the torch, is manned and unmanned orbital, lunar and solar system launch capabilities. Industry is already performing and incentivized to provide these capabilities better than NASA. NASA can best contribute to improving those capabilities, with the least investment, by being a demanding customer.
SpaceX happens to have put itself in the center of those principles, due to a lot of fine work. But the principles make just as good sense, regardless of who the industrial innovators are.
Couldn't that money be put to better use expanding the boundaries of human and machine exploration, instead of being a less efficient redundant effort?
Curious what you think of the SLS.
It's the manned space exploration programs and all the space-as-in-vapid programs that could and should be cut with extreme prejudice.
And in case I need to make myself clear: There is no value in manned space exploration at this point, at least no value that can't be obtained with unmanned programs. I say that as someone who was and will always be fascinated by Apollo, Space Shuttle, et al.
The main thing on the chopping block is all rocket R&D and forcing NASA to contract out that work. It's unlikely Musk would suggest chopping the programs themselves as those are very lucrative contracts SpaceX would be bidding for.
> no value in manned space exploration at this point
Only if you ignore the value of inspiring the next generation of scientists and explorers.
Nearly everything NASA does outside of operating the missions themselves is contracted out, especially the SLS which is all of it:
* The main stage (aka core stage), essentially a repurposed Space Shuttle external fuel tank with engines bolted on, is contracted out to Boeing, with so far one launch and two completed production units in at least ten years of production.
* The main engines, which are refurbished SSMEs used as throwaways, are contracted out to Aerojet Rocketdyne.
* The SRBs are contracted out to Northrop Grumman, and the first eight launches will all be reusing the old Space Shuttle SRBs.
* The second stage, a repurposed Delta IV second stage, is contracted out to United Launch Alliance which is basically Boeing and Lockheed Martin.
* Finally, the Orion is contracted out to Lockheed Martin and Airbus. Incidentally, this is the only "new" component of the program.
https://en.wikipedia.org/wiki/Space_Launch_System
https://en.wikipedia.org/wiki/Orion_(spacecraft)
>Only if you ignore the value of inspiring the next generation of scientists and explorers.
Unmanned programs like Hubble and the other Great Observatories, New Horizons, Spirit/Opportunity/Curiosity, and the two Voyagers inspire the people far more than manned programs.
There was value in manned programs before, we needed to figure out WTF human bodies will do in space. We figured that out at least 20 years ago. Now we need to keep contriving excuses to keep ISS flying and there's barely enough commercial interest in manned space utilization.
No, cut it all. Until we reach the next paradigm shift where we have to send men out into the black again to gain answers, robots can do everything a man could for cheaper, safer, longer, and faster.
Kind of but not quite AFAIK. The design, specification building, and various prototyping happens within NASA. They contract out once they know what they want to build. Musk doesn't have the ability to cancel the SLS. That would require an act of Congress and face all the same obstacles as why the SLS got created in the first place (to save jobs that would have been cut after the cancellation of the shuttle). However, he would be able to cut the design and specification building & prototyping that NASA does and instead force them to contract out for that (preferably to SpaceX).
The entire focus of DOGE seems to be to reduce the number of employees, not to cut programs. The reason for that is also tactical sabotage. It's hard to cut programs because politics gets involved. But if you could mass fire employees so that government can't succeed at those programs, then you can follow up later and point to how government is incompetent and the programs need to be cut since they're not meeting their goals.
> Unmanned programs like Hubble and the other Great Observatories, New Horizons, Spirit/Opportunity/Curiosity, and the two Voyagers inspire the people far more than manned programs.
Unmanned programs inspire people already inclined to science & exploration of the unknown. They do not inspire people who aren't so inclined and who instead look towards heros to show them what's possible or ask "why are we spending any money on space exploration". Said another way, unmanned programs don't inspire people to become astronauts or value spending on research into exploration. Neil Armstrong landing on the moon inspired a lot of people to dream of becoming astronauts and perhaps spark their interest in science in the first place.
That's why the Mars program is important even if scientifically it's of limited value.
One thing I'll highlight. While Musk is a darling for SpaceX today because SpaceX is competing aggressively, over time SpaceX will inevitably morph into the next Boeing and put us back into the same problems if they're allowed to monopolize the government funds.
11AU is outside Saturn's orbit. With the high inclination of the orbit (95 degrees) it's coming in on a more-or-less polar orbit of the sun. You might need a Jupiter flyby along the lines of what Ulysses did to fling it out of the ecliptic plane, but Jupiter might not be in the right place in its orbit to make that work..
And you'd need a very light spacecraft (not much mass budget for instruments) launched very fast, and it's far enough away from the sun that you'd want RTG power rather than solar panels.
13kW solar system installed today.
Finacial incentives eh
How can such a high inclination be explained?
Short period comets are relatively close to the ecliptic, while very-long-period comets have evenly distributed inclinations suggesting that the objects in the Oort are more or less spherically distributed.
Discussed here: https://en.wikipedia.org/wiki/Oort_cloud#Development_of_theo...
[1]. https://i4is.org/project-lyra-a-solar-oberth-at-10-solar-rad...
If you can maintain a constant 1g of acceleration, you'd get to ~0.99c in approximately 1 year -- but you need to carry/provide the energy to fuel whatever propulsion system you're using and the amount of fuel needed to maintain that 1g of acceleration increases as you get closer to c.
[0] https://en.wikipedia.org/wiki/Ion_thruster
[1] https://en.wikipedia.org/wiki/Solar_sail
The Comet Interceptor is a robotic spacecraft mission led by the European Space Agency (ESA) planned for launch in 2029. The spacecraft will be "parked" at the Sun-Earth L2 point and wait for up to three years for a long-period comet to fly by at a reachable trajectory and speed.
https://astrobiology.nasa.gov/news/caltech-researchers-find-...