For Questions That Don't Merit Their Own Thread

[Terwin]

1 minute ago, Spacescifi said:

A plasma dense enough to be as visible as an ion rocket plume. Only along the length of the entiire several thousand k beam

That does not clarify much, as a low-density but electron-rich 'plume' could easily be visible if against a dark background.

Also, the temperature of the plasma maters a great deal.  Even though your fire-place poker has little to fear from a wood fire, it was originally created by being melted in a different(much hotter) fire, and it could be vaporized by an even hotter fire.  And all of those fires have plasma much cooler than the plasma in the heart of the sun.

[kerbiloid]

A question to those who has been vaccinated.

So, can now anybody connect to 5G, or still needs a smartphone?

[DDE]

Those doors, which you can actually see from here, sir, are the problem.

[StrandedonEarth]

8 hours ago, kerbiloid said:

A question to those who has been vaccinated.

So, can now anybody connect to 5G, or still needs a smartphone?

I just got the second jab yesterday, but I’m not getting YouTube piped straight into my brain yet. So the 5G must be still syncing up. Cheap antennas. 

[sevenperforce]

10 hours ago, kerbiloid said:

Idk the gimbal angle limits of the Falcon engines, but SSME is limited with 10.5°, and others are also <= 10°.

cos(10°) ~= 0.985

So, it could decrease the throttle  down to (1 + 2 * 0.985) / (1 + 2) = 0.99 of max, which is just 1 percent of difference.

Oh, you misunderstand. The goal would not be to change throttle, but to alter the expansion pattern without an altitude-compensating nozzle.

Let’s take the Falcon 9 as an example. The SL Merlin 1D is slightly overexpanded at sea level but it rapidly becomes underexpanded as it climbs, eventually creating that very large plume shortly before MECO. That plume from underexpansion represents an efficiency loss.

The nine engines on the Falcon 9 don’t have enough clearance to all angle in together, but if they did, would that direct the plume more in the correct direction and thus increase efficiency?

[Spaceman.Spiff]

9 hours ago, kerbiloid said:

A question to those who has been vaccinated.

So, can now anybody connect to 5G, or still needs a smartphone?

I just have a weird urge to buy Microsoft products. 
 

Renew your Office365 subscription today!

[kerbiloid]

Now I understand why they presented new Windows 11 right now...

[JoeSchmuckatelli]

13 hours ago, kerbiloid said:

5G?

I'm getting it - but my 30 day free trial ended months ago and they've been charging me $80/month ever since.  Apparently you can't opt out or change plans and I've heard the rates are going up soon

Stupid anti-matter question: is it atom per atom of destruction or is it based on mass? 

(can an atom of normal matter H destroy an antimatter O - or will there be leftover antimatter... And if so what?) 

Edited June 27, 2021 by JoeSchmuckatelli

[kerbiloid]

Electron-positron pairs annihilate, too, and they are not atoms.

It's a quark&lepton level of interaction, and the mass is involved only indirectly.

[SOXBLOX]

The hydrogen would cancel with only one antiproton and one antielectron. [Citation needed] Not sure what would happen to the former antioxygen atom, but its remaining parts should survive.

Edited June 27, 2021 by SOXBLOX

[SunlitZelkova]

Apart from simply learning more about it, does Ceres have any value as a target for human exploration?

In the event humans land on Mars sometime between now and 2040, would Ceres make a good "next target"?

Or would human exploration further out just stop? Historically, all space agencies and people have ever really been interested in sending people to are the Moon, Mars, and prior to the realization/discovery about its atmosphere, Venus.

There is a single concept paper about a human mission to Callisto out there, but after a human Mars landing, having actual scientists and engineers seriously discuss sending a human mission to a Jovian moon is a bit hard to imagine.

[MKI]

22 minutes ago, SunlitZelkova said:

Apart from simply learning more about it, does Ceres have any value as a target for human exploration?

In the event humans land on Mars sometime between now and 2040, would Ceres make a good "next target"?

Or would human exploration further out just stop? Historically, all space agencies and people have ever really been interested in sending people to are the Moon, Mars, and prior to the realization/discovery about its atmosphere, Venus.

There is a single concept paper about a human mission to Callisto out there, but after a human Mars landing, having actual scientists and engineers seriously discuss sending a human mission to a Jovian moon is a bit hard to imagine.

I'm on the side of "why send fragile humans anywhere anytime soon?" Sure Mars has the "cool factor", but it's still incredible challenging to get anything to Mars, let alone getting that thing to be a fragile meat bag and find a way to get them back.

 

Humans are useful and all, but robotic missions give way more bang for your buck in all use-cases. Beyond the novelty of actually putting people on the ground, there isn't really any reason to send humans where we can send probes/rovers/landers. Yea its not as cool and all, but humans are just so fragile that the costs to support any individual skyrockets way past any sort of probe(s) you could send to perform the same job(s).

 

There are plenty of targets in our backyard that are more cheaper to get humans too and can provide just as much value, such as NEO's and the Moon itself. Both of which I'd assume have similar science values as Ceres, without the risk of traveling that far out.

 

Until space infrastructure gets to a point where building and maintaining long duration humans in zero-g becomes much cheaper and reliable, sending fragile meat-bags there will continue to be too expensive and risky compared to just sending probes. 

 

[SOXBLOX]

1 hour ago, SunlitZelkova said:

Apart from simply learning more about it, does Ceres have any value as a target for human exploration?

Ceres is basically made of water, and water is like gold in space. So if you want to colonize the Solar System, it's great. IDK on scientific exploration...

[kerbiloid]

They will make artificial people and send them to Ceres.
Because it's too far for both human flight or remote control.

It will become their vault and capital.
With no extradition.

Later they will rebel against the Earth tyranny and start bombing it with steam-propelled frozen balls of clay.

But the humans will aim their near-solar lasers at it and melt the ice.
So, the whole Ceres surface will turn into ocean with floating colonies, and they will lack clay for making the balls.

Then they will start bombing the earth with huge self-propelled water blobs.

While flying, the blobs will  freeze and turn into icebergs.
But on re-entry, they will melt and produce waterfalls from the skies. Mostly into the ocean.

As presumably Ceres has more water than Earth has, the Earth ocean level will start raising.

But humans  will be sending the excessive water to the Moon (steam propelled) and water its surface.

This way the Ceres ocean will migrate to the Moon and make it wet and comfy.

Edited June 29, 2021 by kerbiloid

[SunlitZelkova]

23 hours ago, MKI said:

I'm on the side of "why send fragile humans anywhere anytime soon?" Sure Mars has the "cool factor", but it's still incredible challenging to get anything to Mars, let alone getting that thing to be a fragile meat bag and find a way to get them back.

 

Humans are useful and all, but robotic missions give way more bang for your buck in all use-cases. Beyond the novelty of actually putting people on the ground, there isn't really any reason to send humans where we can send probes/rovers/landers. Yea its not as cool and all, but humans are just so fragile that the costs to support any individual skyrockets way past any sort of probe(s) you could send to perform the same job(s).

 

There are plenty of targets in our backyard that are more cheaper to get humans too and can provide just as much value, such as NEO's and the Moon itself. Both of which I'd assume have similar science values as Ceres, without the risk of traveling that far out.

 

Until space infrastructure gets to a point where building and maintaining long duration humans in zero-g becomes much cheaper and reliable, sending fragile meat-bags there will continue to be too expensive and risky compared to just sending probes. 

 

Oh yes, I recognize that if the goal is pure science, human are useless. I'm sure virtually all of the potential science tasks for the human Mars missions currently under study/early planning can be accomplished by robots.

In the 60s there was a good argument for humans. Probes failed quite frequently and were unreliable. But nowadays, there should be no major obstacles.

My question is within the context of "humans should do the science" because "reasons" (which one could argue is kind of all there is going for human space exploration beyond LEO at this time. In the 60s as I mentioned and prior, there were no robots so the dream of "sending men to the Moon/planets" had to exist- there was no other option for exploration. Such is not the case now, so the whole "let's send humans there" is purely because people who support such an idea want to, not because of any logical reason/requirement. But I digress).

So for those people who think humans should go to Mars, "where do you think they should go after that?" is what I was asking.

This is not to say I do not value your answer or anything. A clarification of my question just happens to partially make up my response to your response, which I found myself wanting to respond to.

[MKI]

4 hours ago, SunlitZelkova said:

So for those people who think humans should go to Mars, "where do you think they should go after that?" is what I was asking.

I think taking the idea of "if we are to send humans somewhere, besides Mars, where should be go" is a good starting point.

In that case Ceres makes the most sense almost by default, as the other options are difficult to send people, or really anything to for that matter. Mercury gets too hot/cold with the increased risk of substantial radiation from being right next to the sun. Venus is an oven hot, and hard to get back from.

This leaves Ceres as the next stop on the list, and due to the vast distance increasing to the outer planets, its substantially an easier target just in regards to flight time.

Now if say we started using Orion drives to fly around the solar system and range and flight time get lessen dramatically to where getting to Jupiter is more reasonable, then I'd personally would like to see people go to Titan and the Ice worlds of Enceladus and Europa to directly search for life. 

 

 

Edited June 30, 2021 by MKI

[kerbiloid]

The humans with aflag should be sent to other planets because otherwise other humans with a flag will be sent there.

The flag can't plant itself.

If it's delivered by a probe, it works less  effectively.

Edited June 30, 2021 by kerbiloid

[magnemoe]

7 hours ago, SunlitZelkova said:

Oh yes, I recognize that if the goal is pure science, human are useless. I'm sure virtually all of the potential science tasks for the human Mars missions currently under study/early planning can be accomplished by robots.

In the 60s there was a good argument for humans. Probes failed quite frequently and were unreliable. But nowadays, there should be no major obstacles.

My question is within the context of "humans should do the science" because "reasons" (which one could argue is kind of all there is going for human space exploration beyond LEO at this time. In the 60s as I mentioned and prior, there were no robots so the dream of "sending men to the Moon/planets" had to exist- there was no other option for exploration. Such is not the case now, so the whole "let's send humans there" is purely because people who support such an idea want to, not because of any logical reason/requirement. But I digress).

So for those people who think humans should go to Mars, "where do you think they should go after that?" is what I was asking.

This is not to say I do not value your answer or anything. A clarification of my question just happens to partially make up my response to your response, which I found myself wanting to respond to.

I do not totally agree here, rovers are slow and has limited capabilities. They are also not cheap, had they been so cheep you could spam them this would change. 
In short an manned mission to moon or mars would be much more capable than probes.  
Problem with an manned mission is cost, however starship could change this  to the point that an manned moon mission becomes cheaper than an advanced rover and would be much more capable.  
Mars is harder to pull off but still relevant. 
Humans would be less useful on an asteroid mission but still an bonus. 

Outer solar system I say we need something better than starship for human missions.
 

[SOXBLOX]

10 minutes ago, magnemoe said:

better than starship

NeRVa StARsHip? 

(We need a trefoil emoji. Pleeeaaase, mods?)

[SunlitZelkova]

1 hour ago, magnemoe said:

I do not totally agree here, rovers are slow and has limited capabilities. They are also not cheap, had they been so cheep you could spam them this would change. 
In short an manned mission to moon or mars would be much more capable than probes.  
Problem with an manned mission is cost, however starship could change this  to the point that an manned moon mission becomes cheaper than an advanced rover and would be much more capable.  
Mars is harder to pull off but still relevant. 
Humans would be less useful on an asteroid mission but still an bonus. 

Outer solar system I say we need something better than starship for human missions.
 

In regards to rover vs. human, I think humans could only perform slightly better. Due to safety reasons, crewed rovers likely will never travel that fast at all. So the distance covered is not much of an improvement. There is a limit to how far you can go away from the lander anyways.

All of my answers/opinions/statements were within the context of government run space exploration, which the citizens of each government obviously have at least some say in. If the government (NASA)'s goal is to explore space and make new discoveries about space (vs. making discoveries about humans in space) then I don't think there is any good argument for humans in space exploration run by the government.

SpaceX is a private company, so even if my and others statements about the uselessness of humans in space exploration were true, I don't think it matters, as SpaceX can go to Mars to do the science "with their own hands", or to build the first Mars colony with the first Mars McDonald's, or just to take selfies and draw pictures in the dirt, if they want to. No logic required as it is their rocket, not mine.

So although I made some statements about humans being unneeded for space exploration, I am not opposed to Starship or anything, because it is not my place to criticize a private company (of which I am not affiliated with)'s plans.

1 hour ago, SOXBLOX said:

NeRVa StARsHip? 

(We need a trefoil emoji. Pleeeaaase, mods?)

Not to turn this into a Starship thread, but there was a discussion about this in the Artemis program thread.

From @cubinator

Quote

Starship tank volume is approximately  a cylinder 9 m diameter and 30 m tall. That volume is 1908 m^3. LH2 density is 71 kg/m^3, so 135 tons of hydrogen would fit in the tanks. Let's now use the trusty rocket equation:

m₀ is 85 tons + fuel mass, m_f is just 85 tons. If you could just fill a Starship's fuel tanks with hydrogen and slap a NTR with I_sp of 1000 on the bottom, you'd get...

9348 m/s

Improved NTR designs might reach I_sp of 1500 (14022 m/s) or 2000 (18696 m/s).  Burning all that would get you to Mars in 2.5 months or less, though stopping once you get there would be a bigger challenge. 

And by @tater

Quote

Which is lower than what it has with CH₄ and LOX (10,120 m/s with 1200t props, 85t dry, and I_sp of 380)

Low density kills H2 as a good prop to drag up from Earth.

CH4 has an Isp of ~640 with NTP, and the density is 423.8kg/m3. Using your same volume and 85t dry mass, I get a NTR SS using CH₄ having 14,830 m/s.

Surprisingly good. Dump the nose off the front, use as a tug stage, and you could give a full SS with 150t cargo ~2400 m/s of dv, and retain >3500m/s of dv to get back to LEO, etc. SS then only has to use ~1500-2000 m/s for a typical Mars transfer (or 800 m/s for TLI). Such a fully loaded SS only has 6,550 m/s of dv to start. If the cargo mass was reduced to closer to 100t, that SS could land on Mars with enough propellant to come back to Earth with no ISRU required. A huge risk mitigation—perhaps this is an early mission where the cargo IS the ISRU gear, or setting it up having landed a cargo ship that will never return anyway.

But rather than using Starship itself to get to the outer planets, I think using rapid-reuse Starship to build a JTV/STV/UTV/NTV (Jupiter/Saturn/Uranus/Neptune Transfer Vehicle) in orbit makes more sense.

[kerbiloid]

2 hours ago, magnemoe said:

starship could change this

Yes. Starship with humans can change everything.

Spoiler

 

[tater]

5 hours ago, SunlitZelkova said:

But rather than using Starship itself to get to the outer planets, I think using rapid-reuse Starship to build a JTV/STV/UTV/NTV (Jupiter/Saturn/Uranus/Neptune Transfer Vehicle) in orbit makes more sense.

I think heavy lift that is cost effective makes lots of things possible. Send NTR transfer vehicle up (with payload on front), then bring more props for it on another trip if required (drop tanks?).

[Terwin]

Looking at Cost-per-science accounting by itself, probes currently make a lot more sense than humans.

Even if a human can get and order of magnitude more science done than a probe in a given time-frame, a probe is probably two orders of magnitude cheaper per time-frame(in part because they can last an order of magnitude longer(or more, looking at you voyager and opportunity) using rtg/solar and in part because it is probably an order of magnitude cheaper without life-support or the ability to come home).

The primary value delivered by human space flight over probes is more related to inspiration(and leveraging national pride to get funding in the first place), not maximizing science per dollar spent.

After all, how many people remember the Luna probes, Ranger probes, or Pioneer 4 compared to Neil Armstrong?

[kerbiloid]

55 minutes ago, Terwin said:

After all, how many people remember the Luna probes, Ranger probes, or Pioneer 4 compared to Neil Armstrong?

Among the 8 billion?

I guess, same number, within the margin of error.

Probably, 200 in USA, maybe 200 in EU, about 100 mln erudites in the other world.

So, 5..6% or so.

Now ask the question in another way: "How many people are sure they never flied to the Moon?"

Edited June 30, 2021 by kerbiloid

[magnemoe]

2 hours ago, Terwin said:

Looking at Cost-per-science accounting by itself, probes currently make a lot more sense than humans.

Even if a human can get and order of magnitude more science done than a probe in a given time-frame, a probe is probably two orders of magnitude cheaper per time-frame(in part because they can last an order of magnitude longer(or more, looking at you voyager and opportunity) using rtg/solar and in part because it is probably an order of magnitude cheaper without life-support or the ability to come home).

The primary value delivered by human space flight over probes is more related to inspiration(and leveraging national pride to get funding in the first place), not maximizing science per dollar spent.

After all, how many people remember the Luna probes, Ranger probes, or Pioneer 4 compared to Neil Armstrong?

For long term observation, probes obviously wins and they are disposable. 
However for an focused study of one site humans has benefits. Like how we tried to drill an hole on Mars to study environment some meter down and seismic. 
It failed, an manned mission would done better here, bring an drill rig and do core samples. 
Yes you could do that with an robotic mission too but the mass, cost and complexity would start getting into manned mission ranges, gold plating will hurt here rater than treat it like belt feed ammo. As in how to get an closer look at the moon poles? drop impactors and have an satellite measure the impact. Or land cheap probes.
Or just put up an base at Shackleton crater as its probably the most valuable prime estate off earth.