Bill Phil
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Posts posted by Bill Phil
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21 minutes ago, tater said:
Very specifically, most electric cars are recharged... at night.
Solar is not so great at night. My buddy has whatever the medium Tesla solar is on his roof, but I don't think he ponied up the 8 grand for the battery pack, so it will offset his AC in summer, and go back to the grid at like $0.005/kWhr (not a typo, think it's a half a cent).
That's another good point. The only solution to address this drawback of solar is grid storage - but that also makes fossil fuel plants more efficient, and more so at that.
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5 hours ago, Kerbart said:
The discussion “driving electric simply moves the exhaust pipe elsewhere” only holds true when that electricity is generated by burning fossil fuel.
The difference with a high efficiency ICE car is that five years from now, that car is still burning fossil fuel. The electric car might at that point be driving on a 50/30/20 mix of solar, nuclear and fossil.
Coal is rapidly dropping as a means to produce electricity. The problem is always the chicken and the egg; you can’t switch to 100% renewable energy sources overnight and neither does an infrastructure that relies on electric (battery) power sprout up overnight.
What the best way to meet demand for electricity will be in the future, time will tell, but it’s becoming increasingly likely that it’s not going to be coal, and unlikely that it’s going to be relying on other fossil fuels for the majority as well.
Assuming “the best” technology will be used is risky. The market preferred VHS over Betamax.
Driving electric doesn't simply move the exhaust pipe everywhere - it's complicated and highly dependent on location.
Coal is losing share as an electricity supply, but it is still in use in many areas.
Fossil fuels are usually how electric demand is met - almost all renewable systems are too intermittent to provide baseload power. Only hydro and geothermal are capable of that.
1 hour ago, wumpus said:Electric cars certainly do more than just move the tailpipe to another neighborhood. High power electric motors are far more efficient than any ICE (typically at least a factor of 2), let alone their high-powered competition. Hybrids are another story, and allow high efficient/low power ICE engines to combine with electric motors (which could be high power).
Efficiency?
Uh oh.
You see, higher efficiency has an interesting consequence - higher consumption. This is almost always the case, even has a name. Jevons paradox.
So more efficient cars in the form of electrics will create an increase in demand for electric power - new capacity will need to be installed. There's about 270 million motor vehicles in the US. Electrifying a decent chunk of the market will lead to more demand for electricity. This is far more likely to be met by natural gas than any renewable system. Once range issues are dealt with this increase in efficiency might also lead to an increase in driving miles, or perhaps an increase in average speed. This will likely lead to an increase in carbon emissions due to an increase in the total power consumed by the grid through EVs.
Electrifying other industries will likely have the same affect.
Even energy storage systems benefit fossil fuel plants far more than renewable plants - coal and natural gas will be able to operate at or near their maximum capacity factor for the duration of their lifespan minus downtime. This will also lead to an increase in carbon emissions.
Unless we do what France did and migrate to a majority nuclear power infrastructure. Efficiency will not save the world. This has to be addressed at every point in the process or it will literally be worse than it is now.
1 hour ago, wumpus said:The problem is "a few generations of nukes" could be an entire century. "A few generations of solar" could be a decade (probably less generations, but still a far, far, faster turnover). One nuke plant is a huge commitment, and it isn't clear who is going to front the money. That said, I've heard there is work being done in India and I can hope for the best.
We don't need to wait a few generations. The technology we have now is well suited to baseload power requirements. We let our nuclear industry die off in the past - it's no wonder new plants are so difficult to start up.
1 hour ago, wumpus said:EU data says that "transportation" creates 25% of the CO2 in Europe (power generation 33%). But "transportation" also produces 60+% of the smog. Granted, as long as China (and Germany*?) burns coal for power that will likely be the main cause of all air pollution (although cars won't help).
https://www.eea.europa.eu/publications/2599XXX/page010.html
* Because nuke plants chill your kidneys** or something, so Germany had to close them down and switch to fossil fuel. And apparently the softest/worst coal they could find.
** Something about German motorcycle riders being afraid of chilling their kidneys. Different places have different superstitions, and the one weird thing I could think of that I've heard Germans believed was "chilled kidneys".
Keep in mind that that "transportation" data likely includes many other sources beyond passenger vehicles. Indeed, semi trucks were responsible for 12.5% of US GHG emissions in 2013. Airplanes and shipping vessels are also large problems globally.
Again, Jevons paradox applies. Electrifying semi trucks will likely lead to an increase in the use of semi trucks, and if the ultimate source of that energy is still fossil fuels (as it is likely to be) then total emissions are likely to still increase, potentially even faster.
Interestingly Germany has been trying to develop their renewable industry - and the amount they've spent likely could have been used to build a large nuclear industry for most of the country. It's actually quite disheartening. Renewables are not the solution to our problems.
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7 minutes ago, wumpus said:
The perfect is the enemy of the good. You're ignoring just how bad an ICE really is, and that a Tesla is more efficient even if the power plant is burning oil. Typically, they burn natural gas which has less emission issues and may have less geopolitical issues as well.
You'll also have to wait a few decades before anybody will consider financing a nuclear power plant. It doesn't make sense to tie up the money for as long as it takes to build a plant and potentially be obsoleted by solar improved by multiple generations (that evolved during constructing that nuke plant).
Perfect may be the enemy of good.
But while an ICE is bad, electrics aren’t inherently better. There are numerous reasons for this. I won’t go into them because there’s already quite a lot of literature on the subject.
Nuclear is better in almost every category than solar except for setup costs. Higher capacity factor, higher EROEI, less deaths per kwh, even less waste not to mention less required ground area. Meanwhile solar gets much more in subsidies per kwh despite not really being an effective power source.
For many places (like where I live) nuclear is really the only option for low emission power. Solar power just doesn’t work out well here. Neither does wind or geothermal. Hydro is already used quite a bit here but it’s not enough.
Thankfully we already have a nuclear plant - the first to generate a gigawatt of electricity and the second most powerful one in the US.
Even the high setup costs may not be inherent with nuclear - a good chunk of the cost is the legal fees and so on associated with starting one.
The issue isn’t oil - it’s coal. Oil isn’t actually all that common for electricity generation - about 1%. Coal is about 27%.
And coal is much less efficient. If your EV is powered by coal then it’s worse than an ICE.
If it’s powered by nuclear it’s far better.
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1 hour ago, Fraston said:
“ROADA ROLLA! MUDAMUDAMUDAMUDAMUDAMUDA WRYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY!!!!“
-Dio Brando, JoJo’s Bizarre Adventure
"ZA WARUDO!"
"KONO DIO DA!"
-DIO
"You're next line is :"
-Joseph Joestar
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9 minutes ago, jinnantonix said:
Boeing doesn't get paid until they deliver against the milestone. Yet they will have fixed outgoings for their permanent staff, and requirements for fixed outcomes against their contractors. So there is actually an incentive to deliver against a timeline, they need to reach the milestone or they run out of cash.
Idk. I’ve heard so many stories from engineers at NASA about Boeing mucking up the works and almost deliberately increasing the required time and actively trying to delay the project.
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14 hours ago, tater said:
Mass drivers work for sturdy cargo, but not humans, as they need to get the things to a decent % of orbital velocity at very low alt (which means huge accelerations).
I'm certainly intrigued by other concepts to space, but if Starship works (huge if), we're talking 10s of dollars per kg to LEO. That's 3 orders of magnitude of improvement in cost.
Starship (and larger cousins, should it work) means that testing things like tethers becomes more possible, too.
The issue isn't acceleration (just build bigger, though of course that isn't easy at all). Acceleration requirements are decreased with distance. It's not the real issue.
The real issue is getting out of the atmosphere.
Dynamic pressure and hypersonic affects at sea level would be monstrous, so you have to build it high up. But that presents an even larger challenge.
That said solutions do exist - though getting them to work would require a lot of engineering and R&D. Launch Loop is one example, and at least has the benefit of being able to use known materials (unlike a space elevator).
I hope Starship works, but there's a good chance it won't. And even if it does rockets are a fairly inefficient use of energy. From an energy economics perspective they'll never be quite as good as non-rocket systems can be. Not to mention the pollution aspects, which are minor for now. But if the launch industry expands massively that'd be a lot of pollution we'd have to deal with, unless we stop using chemical rockets altogether.
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Quote
I design magic rocks that sing.
-Keith Lofstrom, describing his work on electronics as silly as possible
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24 minutes ago, tater said:
Orion (or any nuclear spacecraft with decent dv) would be a helluva thing to see.
I still think seeing SS/SH succeed would be my ultimate realistic hope for my lifetime—precisely because if they get it to actually work, it resets what is possible. Artemis? LOL. 150 tonnes cheaply to LEO is a game changer---and there is no reason that 9m is any sort of limit, bump it to 12m (after 9m works), and we're back to a 400t+ cargo ITS.
Certainly. It would really change the game if it works out.
Though I'm a bit skeptical that rockets will be how civilization breaks the chains of gravity - barring some major advances in the technology rocketry hit diminishing returns some time ago in terms of performance. Non-rocket systems seem to be much more capable, though they require more investment and technological development. At least rockets are a demonstrated technology - the question is lowering the costs. But I wonder if that's truly possible.
That said there was some interesting mass driver research in the 30s that seems to have been buried.
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52 minutes ago, magnemoe said:
0.1 c required using 10 km pusher plates and gigaton 3 or 4 stage fusion bombs.
An medusa setup would be much more practical here I think and this is much more an back of the envelope project than something like the battleship orion.
If you can push stuff up to 0.1c you don't need orion who is an brute force solution.
Your launcher is more dangerous than high yield nuclear bombs.
Well the idea would be to propel a huge ship.
One could adapt mini-mag Orion to the concept - that way at least the propulsion units aren’t full blown nuclear weapons.
Though eventually you get more propulsion from the direct momentum exchange between the propulsion unit and the vehicle.
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1 hour ago, StrandedonEarth said:
Could Orion’s pusher plate also be used for laser-riding? Granted, the huge mass of Orion (the bigger the better) works against using light (the lighter the better), but ablatives would increase the thrust.
Are there any current technological limits on just how big a laser (gigs/tera/petawatt-class?) can get, given a sufficient power supply?
That’s kinda sorta what Lightcraft is.
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1 hour ago, wumpus said:
* I've seen the .1c number since Carl Sagan made Cosmos, but have never really seen the exhaust velocity of the nukes nor just how much fuel you need to deal with the rocket equation for such a number. I suspect this is a "using unobtanium or all the He3 on the moon" value.
0.1c assumes fusion bombs.
That said it is possible using catapulted bombs that the vehicle doesn't carry within itself...
Of course that would imply being able to sling atom bombs at near 0.1c. Yikes.
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3 minutes ago, Barzon said:
a. SLS has higher thrust than the Saturn V
b. It has only a few tons less than the Saturn V with BOLE and EUS.
Higher thrust - and lower total impulse.
It has 26 tonnes for TLI Block 1 - almost half of the Saturn V’s. Block 1b is 40 tonnes or less. Only Block 2 - which may never be developed, approaches the Saturn V’s performance, at 45 tonnes.
Meanwhile the Saturn V could deliver over 48 tonnes to TLI.
Block 2 requires advanced boosters - there’s a real chance it will never happen.
The use of liquid hydrogen in this way is immensely inefficient - gravity losses are larger and the stage delta-v split is inefficient. The higher thrust is all from the SRBs - which have a shorter burn time than the S-IC and provide less total impulse even with the core added.
SLS is less powerful.
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I’ve talked with some of the engineers - it’s a real mess.
Boeing has been very problematic for the engineers so far. I’ve forgotten the specific issues but it’s been a huge problem plaguing SLS since the beginning.
It’s actually going to be one of the cheapest super heavy launchers in terms of development costs. Of course SpaceX may change that but we’ll have to wait.
SLS is less powerful than the Saturn V - the claim that it’s more powerful is just false.
It also has issues with poorly done hardware installation and even hydrostatic pressure. The core is too tall. It doesn’t have enough engines either. Even the software is having issues.
The idea of using “off the shelf” technology didn’t pan out - they had to redesign almost everything and each RS-25 performs slightly differently.
But the real killer is launch cadence. The expected launch rate is so small and the payload capacity so limited as to make the thing almost useless for beyond LEO.
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NASA regularly assists SpaceX and SpaceX is a major NASA contractor.
3 hours ago, Dirkidirk said:in general they are both great and cannot be compared, however when it comes to their rockets spaceX wins.
NASA doesn’t build rockets. At most it designs them and then contracts out the actual construction - but even the engineering has contractors involved.
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14 hours ago, Starman4308 said:
Moon: Close enough for reasonable tourism, may be a source of He3
No, the Moon is a bad source for Helium-3. Uranium and Thorium are more abundant by orders of magnitude and in similar abundances as Earth's surface.
The concentration of Helium-3 on the Moon is so miniscule that it may not even be an energy positive process, and no matter what the energy return on investment will be tiny.
No, there's really nothing in space worth bringing back.
That said a mature industry in space would be awesome and could enable some very interesting missions.
14 hours ago, Starman4308 said:Overall, I don't really see reasons to visit anything other than the Moon, near-Earth asteroids, and possibly Mars until the relevant technology is basically sci-fi level. I dislike speculating beyond there, because by that point, we don't know what the limiting factors and tradeoffs will be.
Well Mini-Mag Orion could open up Jupiter exploration, and if not it would certainly open up Asteroid Belt exploration.
Not sci-fi at all. Though a mature industry in space would certainly help.
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35 minutes ago, Dale Christopher said:
dudes... im not trying to discourage whatever you think is cool. if you like the idea of orbital cities great. I like the idea of bringing life and civilization to mars, but I'm not going to have a discussion about which is better on the eve of the SpaceX abort test... it's too much like an us vs them debate about the aspirations of SpaceX vs BlueO. We can do both \o/, it's weird that it's a one or the other issue...
It's not about how cool it is (it is cool in my mind though). It's about how important Mars will be in the solar system.
Settling Mars is certainly cool and has a romantic allure (especially since a number of old sci-fi books are set on Mars).
This isn't the place to have that discussion anyways. It just seems to me that Starship is more likely to lead to orbital habitats than Mars settlement - and even then both are not likely to happen.
Space settlement is very hard to do. So difficult that we literally do not have the technology. We likely have the science and most of the understanding to do it, but not the technology. And developing that technology may take the better part of this century. Or longer.
Maybe we'll get lucky and the technology will be developed relatively soon, but I doubt it.
In the interim we should be developing an industrial capacity in space - allowing construction of large objects and efficient transportation around the Earth-Moon system. Hopefully both Starship and whatever BO does will help with this.
15 minutes ago, mikegarrison said:If we could build a planet's worth of orbital habitats, we could probably also terraform whole planets pretty easily. Both ideas are so far away from our current capabilities that they make no sense right now.
Not quite.
Terraforming Mars for example requires massive amounts of oxygen and nitrogen (more per square meter than Earth due to the lower gravity) and likely massive reprocessing of the soil. Imagine doing that for 150 million square kilometers!
For a comparable area of space habitats you can have less oxygen and nitrogen per square meter and it is much easier to landscape.
Essentially you're comparing making one giant thing with millions of smaller things - eventually you may see amortization with the difficulties and costs for making the smaller things. Indeed in the best case scenario you can also build the equivalent area faster - if a habitat has 100 square kilometers and is capable of building another in ten years (and we also expand the resource acquisition to support this manufacturing) then one habitat will result in the equivalent area of Mars in a few centuries whereas terraforming Mars may require over a thousand years and even then people may require breathing masks to go outside. But then here's the thing - the space settlements don't have to stop there. Another few doubling periods and you've already built more area than Mars can provide.
Of course a 10 year doubling period is quite optimistic, but the point stands - building a planet's worth of orbital habitats is likely easier to do than terraforming planets. Plus you can build even more area.
Terraforming Mars piecemeal may be possible and may be done but there's a gravity issue and you only get 1 Mars worth of area out of it in the end.
Yes both concepts are beyond current needs to an extreme. But the orbital habitat concept has more room to expand and can be built anywhere in the solar system, if the materials are provided. Plus it can be used to settle any star system so long as it has asteroids or other easily accessible matter sources.
Also the required mass for building an equivalent area to Mars with orbital habitats would represent about 4.1E-5 times the Moon's mass. Dismantling the Moon could enable us to build 20 thousand times Mars's current land area (which is roughly equal to Earth's land area). Of course that's a bad idea (for Earth's ecosystems) and would require a massive infrastructure, but we could build an equivalent area to Mars without having to do much beyond Earth's gravity well (you'd need to probably grab asteroids to get enough nitrogen and water among other volatiles - but there's plenty of oxygen on the Moon at least).
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Awesome.
Getting a lot of cool stuff lately. Keep it up.
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Just now, Dale Christopher said:
O_o.... does not compute
What does Mars really offer us?
Some more land area?
No, it's completely uninhabitable - without our intervention. If we're going to do that though then we'll get so much more bang for our buck by building artificial habitats that rotate to provide artificial gravity (plus you get access to a full 1g of gravity).
A simple calculation using the mass of the Asteroid belt shows that we can build over 700 times the land area of Earth from just that mass. Mars is a drop in the bucket in comparison.
Obviously such a large endeavor will take an immense amount of time and effort but Mars just doesn't offer that much and suffers the same issues as Earth in addition to low gravity and less area - not much habitable area (all of which will be artificial). And since all artificial habitats (no matter the location) will be artificial, orbit is just easier.
Another thing to consider is relative difficulty - the largest object in Earth orbit is the ISS at over 400 tonnes. Meanwhile the largest object on Mars is around 1 tonne. Now this may change with Starship but no matter what happens Starship will also vastly reduce the costs for Earth orbit as well as Mars and the Moon - assuming everything goes perfectly. This means that larger objects in Earth orbit will be possible. It also means a lunar infrastructure could be done somewhat easier. This ends up making orbital habitats around Earth an even more likely prospect, especially since the technology can be somewhat related to orbital hotels - if such an industry ever comes to fruition.
Recently Al Globus found that the radiation environment in equatorial LEO is fairly mild due to avoiding the South Atlantic Anomaly (where radiation spikes).
If we wanted to compare the costs and difficulty of putting a settlement of equal size into either location then it will be much easier to put it into ELEO than on Mars, and this only becomes more true with the introduction of Starship. Not to mention the advantages of being close to Earth - emergencies are easier to deal with, people can return to Earth, maybe visit relatives, and so on (provided Starship can actually make space access cheap enough).
2 minutes ago, Dale Christopher said:ok, i'll go to mars you start building a space city. best of luck
I've said before that the ISS is the second most habitable place in the solar system - and even then it's a very far second to Earth. I'd take a space city over Mars any day.
At least then I have a better chance of coming back to Earth if things go awry.
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8 hours ago, cubinator said:
For me, Mars is important not just on its own as a destination but as a gateway to the rest of the solar system. If we can develop two-way transport between Earth and Mars, we'll be able to go anyplace in the solar system and stay there. And once we do that we'll be well on our way to building interstellar ships. That's why colonization of Mars is a big deal.
Mars isn't that much of a gateway - it's one of many possible destinations.
Earth orbit is more of a gateway than any other location. From there both Venus and Mars aren't far in terms of delta-v. And there's actually quite a lot we can do as a civilization in just the Earth-Moon system. Indeed the thermodynamics of civilization may necessitate activities that are quite interesting in this "region" of the solar system. And if beamed propulsion or even just advanced nuclear propulsion is developed and the required energy infrastructure with it then transportation in the solar system becomes easier (in a relative sense since we will be a more energy rich society - hopefully).
Interstellar vehicles are... difficult. We're talking immense energies (for both low mass high velocity vehicles and high mass low velocity vehicles, the scaling relationship isn't very nice).
I really feel that colonization of Mars will ultimately be a footnote. Orbital habitats just have so much more to offer an energy rich society than any planet. It'll happen eventually, but I doubt it'll be a major event. Rather it'll be a long process that coincides with other efforts but brings less benefits.
8 hours ago, tater said:The ability to use the solar system is another matter. I get that, and support it, but I would need to see a case for the economics of it that isn't fantasy.
Economics may never work out for space settlement. However thermodynamics will eventually rear its ugly head if our energy use grows (and since standard of living correlates quite well to energy use per capita I would argue it should grow, but with less damaging sources). Eventually our civilization may overload Earth's heat rejection capacity. Before that ever happens I would argue that we should be a space-based civilization - with major industries no longer on the planet and perhaps even major populations as well. This is because if we want to stay on the planet and remain a high energy society we will need to invent some way to increase Earth's heat rejection capacity - it's not impossible but it seems even less economically sound than expansion into space. That is to say that methods for launching large volumes of mass into space (and at survivable accelerations) are much easier to develop than a massive thermal control system for the entire planet.
Of course civilization may collapse long before it ever threatens to overload Earth's heat rejection capacity.
Essentially it may be more costly to remain on Earth than to expand into space - a few centuries or maybe even millennia from now.
On a more SpaceX related note:
Hope Crew Dragon turns out well. Would be awesome to have more manned vehicles up.
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9 hours ago, Ultimate Steve said:
The real fun starts after we build a working nuclear fusion thermal rocket engine. Specific impulses measured in tens of thousands unlock a lot of options.
Just workable power producing fusion reactors are still a ways off, but those will probably happen in my lifetime. From there it is a lot more work to get it workable in a rocket engine, but one can hope.
Don't need fusion for that.
Z-Pinch fission can get up to 20 thousand seconds, and fusion boosted fission (using fusion reactions to increase the neutron flux to increase fission burnup rate) could get above 100 thousand seconds.
Could even make it like VASIMR/LANTR - adding in an "afterburner" to get more thrust when it's useful. Of course most of that usefulness is either escaping a gravity well or launching from a planet - which is probably never going to happen with nuclear propulsion.
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Then wait for a sale.
You can hide the struts pretty well if you’re careful.
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55 minutes ago, tater said:
Came here to post this:
$#@! cancer.
Neil Peart stands alone.
Rest in Peace
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Just now, Spacescifi said:
Clever. There is nothing stopping you from accelerating along the way while you spool up the jump drive... although that requires information about the planet you're traveling to and not just jumping in blind like in Star Trek.
Question... would the crew feel ANY g-force while doing orbital gravity slingshots with engines off?
I tend to think no, but would they?
I mean the ISS experiences just enough g-force to keep them in a low orbit, but the crew does not feel any weight at all.
In free fall no force is felt except tidal forces, which can be minimized.
As an answer to the OP:
100 km/s at 1g is about 10 thousand seconds. Or about 2.8 hours.
The one space mission you'd most like to see in your lifetime
in Science & Spaceflight
Posted
12 people, only 1 of which was an actual scientist.
We’ve barely been to the Moon at all.