Will it be possible to see BFR approaching the moon from earth, with naked eye?











up vote
14
down vote

favorite












The title pretty much sums it up. I'm not old enough to have experienced any of the previous manned moon landings. Given that Big Falcon Rocket will go around the moon in 2023, I'm wondering if one will be able to see the whole rocket or at least its second stage from earth when it's approaching the moon - but with my plain eyes (I know camera technology's good).



I'm not expecting to see it like a plane or something, but maybe reflections, thrusters, ...? A tiny dot getting closer and closer to the moon, knowing there are humans in there - that'd be cool...



Thanks in advance!










share|improve this question







New contributor




linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
















  • 2




    Thank you for the accept, but don't feel you have to accept right away. It's possible other good answers will be posted as well.
    – uhoh
    Nov 17 at 12:43






  • 1




    Sure - I got used to accepting quite fast from SO, but you're right, on many other SE sites there's often way more room for multiple correct and good answers, let's see :)
    – linusg
    Nov 17 at 12:49








  • 1




    Yep, this is a different galaxy than SO! ;-)
    – uhoh
    Nov 17 at 12:52










  • Hi new user! The simple answer is no, not a chance. Not even close. It would be like trying to see a cellphone from about 100 miles away.
    – Fattie
    Nov 17 at 16:47










  • You may enjoy this, OP .. what-if.xkcd.com/13
    – Fattie
    Nov 17 at 16:51















up vote
14
down vote

favorite












The title pretty much sums it up. I'm not old enough to have experienced any of the previous manned moon landings. Given that Big Falcon Rocket will go around the moon in 2023, I'm wondering if one will be able to see the whole rocket or at least its second stage from earth when it's approaching the moon - but with my plain eyes (I know camera technology's good).



I'm not expecting to see it like a plane or something, but maybe reflections, thrusters, ...? A tiny dot getting closer and closer to the moon, knowing there are humans in there - that'd be cool...



Thanks in advance!










share|improve this question







New contributor




linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
















  • 2




    Thank you for the accept, but don't feel you have to accept right away. It's possible other good answers will be posted as well.
    – uhoh
    Nov 17 at 12:43






  • 1




    Sure - I got used to accepting quite fast from SO, but you're right, on many other SE sites there's often way more room for multiple correct and good answers, let's see :)
    – linusg
    Nov 17 at 12:49








  • 1




    Yep, this is a different galaxy than SO! ;-)
    – uhoh
    Nov 17 at 12:52










  • Hi new user! The simple answer is no, not a chance. Not even close. It would be like trying to see a cellphone from about 100 miles away.
    – Fattie
    Nov 17 at 16:47










  • You may enjoy this, OP .. what-if.xkcd.com/13
    – Fattie
    Nov 17 at 16:51













up vote
14
down vote

favorite









up vote
14
down vote

favorite











The title pretty much sums it up. I'm not old enough to have experienced any of the previous manned moon landings. Given that Big Falcon Rocket will go around the moon in 2023, I'm wondering if one will be able to see the whole rocket or at least its second stage from earth when it's approaching the moon - but with my plain eyes (I know camera technology's good).



I'm not expecting to see it like a plane or something, but maybe reflections, thrusters, ...? A tiny dot getting closer and closer to the moon, knowing there are humans in there - that'd be cool...



Thanks in advance!










share|improve this question







New contributor




linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











The title pretty much sums it up. I'm not old enough to have experienced any of the previous manned moon landings. Given that Big Falcon Rocket will go around the moon in 2023, I'm wondering if one will be able to see the whole rocket or at least its second stage from earth when it's approaching the moon - but with my plain eyes (I know camera technology's good).



I'm not expecting to see it like a plane or something, but maybe reflections, thrusters, ...? A tiny dot getting closer and closer to the moon, knowing there are humans in there - that'd be cool...



Thanks in advance!







spacex the-moon bfr visibility-of-spacecraft






share|improve this question







New contributor




linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|improve this question







New contributor




linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|improve this question




share|improve this question






New contributor




linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









asked Nov 17 at 11:29









linusg

1766




1766




New contributor




linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





New contributor





linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






linusg is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.








  • 2




    Thank you for the accept, but don't feel you have to accept right away. It's possible other good answers will be posted as well.
    – uhoh
    Nov 17 at 12:43






  • 1




    Sure - I got used to accepting quite fast from SO, but you're right, on many other SE sites there's often way more room for multiple correct and good answers, let's see :)
    – linusg
    Nov 17 at 12:49








  • 1




    Yep, this is a different galaxy than SO! ;-)
    – uhoh
    Nov 17 at 12:52










  • Hi new user! The simple answer is no, not a chance. Not even close. It would be like trying to see a cellphone from about 100 miles away.
    – Fattie
    Nov 17 at 16:47










  • You may enjoy this, OP .. what-if.xkcd.com/13
    – Fattie
    Nov 17 at 16:51














  • 2




    Thank you for the accept, but don't feel you have to accept right away. It's possible other good answers will be posted as well.
    – uhoh
    Nov 17 at 12:43






  • 1




    Sure - I got used to accepting quite fast from SO, but you're right, on many other SE sites there's often way more room for multiple correct and good answers, let's see :)
    – linusg
    Nov 17 at 12:49








  • 1




    Yep, this is a different galaxy than SO! ;-)
    – uhoh
    Nov 17 at 12:52










  • Hi new user! The simple answer is no, not a chance. Not even close. It would be like trying to see a cellphone from about 100 miles away.
    – Fattie
    Nov 17 at 16:47










  • You may enjoy this, OP .. what-if.xkcd.com/13
    – Fattie
    Nov 17 at 16:51








2




2




Thank you for the accept, but don't feel you have to accept right away. It's possible other good answers will be posted as well.
– uhoh
Nov 17 at 12:43




Thank you for the accept, but don't feel you have to accept right away. It's possible other good answers will be posted as well.
– uhoh
Nov 17 at 12:43




1




1




Sure - I got used to accepting quite fast from SO, but you're right, on many other SE sites there's often way more room for multiple correct and good answers, let's see :)
– linusg
Nov 17 at 12:49






Sure - I got used to accepting quite fast from SO, but you're right, on many other SE sites there's often way more room for multiple correct and good answers, let's see :)
– linusg
Nov 17 at 12:49






1




1




Yep, this is a different galaxy than SO! ;-)
– uhoh
Nov 17 at 12:52




Yep, this is a different galaxy than SO! ;-)
– uhoh
Nov 17 at 12:52












Hi new user! The simple answer is no, not a chance. Not even close. It would be like trying to see a cellphone from about 100 miles away.
– Fattie
Nov 17 at 16:47




Hi new user! The simple answer is no, not a chance. Not even close. It would be like trying to see a cellphone from about 100 miles away.
– Fattie
Nov 17 at 16:47












You may enjoy this, OP .. what-if.xkcd.com/13
– Fattie
Nov 17 at 16:51




You may enjoy this, OP .. what-if.xkcd.com/13
– Fattie
Nov 17 at 16:51










3 Answers
3






active

oldest

votes

















up vote
17
down vote



accepted










tl;dr: at an apparent magnitude of about +18.5 you need a several meter telescope and a dark sky. Hubble can do it too. So by reflected sunlight, definitely not by eye. The exhaust from a Methalox (CH4 + LOX) engine barely makes any light in the visible, so no help there.





Starting with the math from this answer:



I'm going to characterize the 55 x 9 meter white 2nd stage as a 22 meter diffuse sphere(ical cow) with albedo 0.3 for order of magnitude estimation.




The expression for absolute magnitude $M_{Abs}$ by rearranging the equation here is:



$$M_{Abs} = 5 left(log_{10}(1329) -frac{1}{2}log_{10}(text{albedo}) -log_{10}(D_{km})right)$$




For the "spherical cow" spacecraft that turns out to be an absolute magnitude of +25.




Knowing the absolute magnitude of an object, you calculate the apparent magnitude $m$ using:



$$ m = M_{Abs} + 2.5 log_{10}left(frac{d_{SR} d_{RE}}{1 text{AU}^2 O(1)}right), $$



where $d_{SR}$ and $d_{RE}$ are the Sun-Roadster and Roadster-Earth distances, each normalized by 1 AU, and the factor $O(1)$ is the phase integral, of order unity, taking into account the angular difference between the direction of illumination and the direction of viewing. In an order of magnitude calculation, this only becomes really significant when the body moves between the Sun and the viewer. See https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_System_bodies_(H).




In this case, replace Roadster with BFR. Since $d_{SR}$ and $d_{RE}$ are 1.0 and 0.0025 AU respectively, and ignoring the phase integral, the apparent magnitude is about -6.5 lower or +18.5 magnitude.



I think that can be seen with the Hubble Space Telescope above the atmosphere in a fairly short exposure. On the ground you'd need a several meter telescope and a dark night, but you can do it. If you want to use your eye, better find one of these telescopes that has an active eyepiece!



BFR's Raptor engines burn "methalox" (methane and liquid oxygen) CH4 + O2. The products are CO2 and H2O both gases. The brightness from the exhaust from many launches are from carbon soot glowing when kerosene (RP-1) is burned, not methane.





Here is a screenshot from the video Blue Origin BE-4 Engine Compilation during the daytime, so you can have a reference to brightness. I haven't found an outdoor firing of the Raptor yet:



Screenshot Blue Origin BE-4 Engine Compilation






share|improve this answer



















  • 1




    Thanks for the detailed answer, especially your addition about the engine chemistry! I'm not a native english speaker, but after I look up some of the physics vocabulary used I'll have a more in depth look on the formulas!
    – linusg
    Nov 17 at 12:47






  • 1




    Feel free to ask me to make something clearer here, or you can post a new question about the calculations after checking the links. Welcome to Space!
    – uhoh
    Nov 17 at 12:51








  • 2




    The shuttle main engines burned liquid hydrogen, not methane
    – matteol
    Nov 17 at 13:15










  • @matteol I knew something felt strange there, thanks!
    – uhoh
    Nov 17 at 13:18








  • 1




    Doesn't New Shepard use the BE-3, which is hydrolox? Did they test it with the BE-4?
    – DylanSp
    Nov 17 at 18:21


















up vote
14
down vote













If you want an easy way to think about it, imagine how bright it might be in low Earth orbit, 240 miles up (which is just a bit lower than the International Space Station). However bright that is, it will be only a millionth as bright when it’s near the Moon, 240,000 miles away (and so a thousand times the distance). Is it likely that it will be bright enough in low orbit that you can still see it when it’s a millionth as bright as that?






share|improve this answer








New contributor




Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.


















  • Good one Mike. I figure you can "see a cellphone" from about 1/10th of a mile. So I said it would be like trying to see a cellphone at 100 miles. Sounds about right?
    – Fattie
    Nov 17 at 16:48










  • @Fattie It’s about right, but the crucial point is that something a thousand times further away isn’t a thousand times dimmer, it’s a million times dimmer. Inverse square law.
    – Mike Scott
    Nov 17 at 17:20






  • 5




    You got the same answer as I did with about a thousand times less work, congratulations! One million times dimmer is 15 magnitudes dimmer. Start with 3rd magnitude and add 15 and you get 18. +1
    – uhoh
    Nov 17 at 18:04






  • 4




    @linusg I think that this is a better answer than mine, because it's just as correct, but a lot more accessible.
    – uhoh
    Nov 17 at 18:06


















up vote
4
down vote













Rocket engines burning in vacuum produce large exhaust plumes that rapidly spread outward to 'fill' the vacuum. This means that for a distance of many dozens of meters - or more - they produce a visible cloud of gas that can catch sunlight and produce very large, visible artifacts in a clear night sky. So - engine burns near Earth (departure, or arrivals burning into orbit) will be quite easily visible to those who are in night and under the burns.



For example, this GLONASS launch trail taken from a thread full of rocket plume images. GLONASS launch trail



Mid course burns may be visible as well, though much less dramatic. Arrival and departure burns happening in the vicinity of the moon are not likely to be visible at all to the naked eye due to great distance.






share|improve this answer

















  • 2




    I am not sure that CO2 + H2O exhaust in vacuum would ever form a visible plume. Without a buffer gas (i.e. low pressure atmosphere) to slow it quickly, wouldn't the molecules expand to large separation distances and have no chance to recombine into droplets?
    – uhoh
    Nov 18 at 2:00






  • 1




    I can't find suitable evidence for my hunch they will remain visible. Gaseous nitrogen thrusters produce visible plumes. Fuel dumps are visible, though that contains liquid fuel. I believe water vapor will produce visible ice crystals, but this is just my hunch.
    – Saiboogu
    Nov 18 at 15:26






  • 1




    @uhoh Wouldn't they flash-freeze into tiny crystals with pressure drop in vacuum?
    – Eth
    2 days ago










  • @Eth It's a race. If the molecules bump into each other frequently enough, they can stick and start forming particles, but if their relative velocity moves them far enough apart fast enough so that collisions are infrequent, then they won't. They won't slow down in vacuum. Watch launch videos and especially the views behind 2nd stages where you see the red-hot nozzle and the path back to Earth, RP-1/LOX engines don't seem to leave any trail behind themselves at all, and that's very similar chemistry to methalox.
    – uhoh
    2 days ago










  • RP-1/LOX engines don't produce a plume visible from the vehicle's POV, but they produce plumes that are exceptionally visible when lit by sunlight against a dark sky (see any SpaceX sunset/sunrise launch).
    – Saiboogu
    yesterday













Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "508"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});






linusg is a new contributor. Be nice, and check out our Code of Conduct.










 

draft saved


draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fspace.stackexchange.com%2fquestions%2f32064%2fwill-it-be-possible-to-see-bfr-approaching-the-moon-from-earth-with-naked-eye%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























3 Answers
3






active

oldest

votes








3 Answers
3






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
17
down vote



accepted










tl;dr: at an apparent magnitude of about +18.5 you need a several meter telescope and a dark sky. Hubble can do it too. So by reflected sunlight, definitely not by eye. The exhaust from a Methalox (CH4 + LOX) engine barely makes any light in the visible, so no help there.





Starting with the math from this answer:



I'm going to characterize the 55 x 9 meter white 2nd stage as a 22 meter diffuse sphere(ical cow) with albedo 0.3 for order of magnitude estimation.




The expression for absolute magnitude $M_{Abs}$ by rearranging the equation here is:



$$M_{Abs} = 5 left(log_{10}(1329) -frac{1}{2}log_{10}(text{albedo}) -log_{10}(D_{km})right)$$




For the "spherical cow" spacecraft that turns out to be an absolute magnitude of +25.




Knowing the absolute magnitude of an object, you calculate the apparent magnitude $m$ using:



$$ m = M_{Abs} + 2.5 log_{10}left(frac{d_{SR} d_{RE}}{1 text{AU}^2 O(1)}right), $$



where $d_{SR}$ and $d_{RE}$ are the Sun-Roadster and Roadster-Earth distances, each normalized by 1 AU, and the factor $O(1)$ is the phase integral, of order unity, taking into account the angular difference between the direction of illumination and the direction of viewing. In an order of magnitude calculation, this only becomes really significant when the body moves between the Sun and the viewer. See https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_System_bodies_(H).




In this case, replace Roadster with BFR. Since $d_{SR}$ and $d_{RE}$ are 1.0 and 0.0025 AU respectively, and ignoring the phase integral, the apparent magnitude is about -6.5 lower or +18.5 magnitude.



I think that can be seen with the Hubble Space Telescope above the atmosphere in a fairly short exposure. On the ground you'd need a several meter telescope and a dark night, but you can do it. If you want to use your eye, better find one of these telescopes that has an active eyepiece!



BFR's Raptor engines burn "methalox" (methane and liquid oxygen) CH4 + O2. The products are CO2 and H2O both gases. The brightness from the exhaust from many launches are from carbon soot glowing when kerosene (RP-1) is burned, not methane.





Here is a screenshot from the video Blue Origin BE-4 Engine Compilation during the daytime, so you can have a reference to brightness. I haven't found an outdoor firing of the Raptor yet:



Screenshot Blue Origin BE-4 Engine Compilation






share|improve this answer



















  • 1




    Thanks for the detailed answer, especially your addition about the engine chemistry! I'm not a native english speaker, but after I look up some of the physics vocabulary used I'll have a more in depth look on the formulas!
    – linusg
    Nov 17 at 12:47






  • 1




    Feel free to ask me to make something clearer here, or you can post a new question about the calculations after checking the links. Welcome to Space!
    – uhoh
    Nov 17 at 12:51








  • 2




    The shuttle main engines burned liquid hydrogen, not methane
    – matteol
    Nov 17 at 13:15










  • @matteol I knew something felt strange there, thanks!
    – uhoh
    Nov 17 at 13:18








  • 1




    Doesn't New Shepard use the BE-3, which is hydrolox? Did they test it with the BE-4?
    – DylanSp
    Nov 17 at 18:21















up vote
17
down vote



accepted










tl;dr: at an apparent magnitude of about +18.5 you need a several meter telescope and a dark sky. Hubble can do it too. So by reflected sunlight, definitely not by eye. The exhaust from a Methalox (CH4 + LOX) engine barely makes any light in the visible, so no help there.





Starting with the math from this answer:



I'm going to characterize the 55 x 9 meter white 2nd stage as a 22 meter diffuse sphere(ical cow) with albedo 0.3 for order of magnitude estimation.




The expression for absolute magnitude $M_{Abs}$ by rearranging the equation here is:



$$M_{Abs} = 5 left(log_{10}(1329) -frac{1}{2}log_{10}(text{albedo}) -log_{10}(D_{km})right)$$




For the "spherical cow" spacecraft that turns out to be an absolute magnitude of +25.




Knowing the absolute magnitude of an object, you calculate the apparent magnitude $m$ using:



$$ m = M_{Abs} + 2.5 log_{10}left(frac{d_{SR} d_{RE}}{1 text{AU}^2 O(1)}right), $$



where $d_{SR}$ and $d_{RE}$ are the Sun-Roadster and Roadster-Earth distances, each normalized by 1 AU, and the factor $O(1)$ is the phase integral, of order unity, taking into account the angular difference between the direction of illumination and the direction of viewing. In an order of magnitude calculation, this only becomes really significant when the body moves between the Sun and the viewer. See https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_System_bodies_(H).




In this case, replace Roadster with BFR. Since $d_{SR}$ and $d_{RE}$ are 1.0 and 0.0025 AU respectively, and ignoring the phase integral, the apparent magnitude is about -6.5 lower or +18.5 magnitude.



I think that can be seen with the Hubble Space Telescope above the atmosphere in a fairly short exposure. On the ground you'd need a several meter telescope and a dark night, but you can do it. If you want to use your eye, better find one of these telescopes that has an active eyepiece!



BFR's Raptor engines burn "methalox" (methane and liquid oxygen) CH4 + O2. The products are CO2 and H2O both gases. The brightness from the exhaust from many launches are from carbon soot glowing when kerosene (RP-1) is burned, not methane.





Here is a screenshot from the video Blue Origin BE-4 Engine Compilation during the daytime, so you can have a reference to brightness. I haven't found an outdoor firing of the Raptor yet:



Screenshot Blue Origin BE-4 Engine Compilation






share|improve this answer



















  • 1




    Thanks for the detailed answer, especially your addition about the engine chemistry! I'm not a native english speaker, but after I look up some of the physics vocabulary used I'll have a more in depth look on the formulas!
    – linusg
    Nov 17 at 12:47






  • 1




    Feel free to ask me to make something clearer here, or you can post a new question about the calculations after checking the links. Welcome to Space!
    – uhoh
    Nov 17 at 12:51








  • 2




    The shuttle main engines burned liquid hydrogen, not methane
    – matteol
    Nov 17 at 13:15










  • @matteol I knew something felt strange there, thanks!
    – uhoh
    Nov 17 at 13:18








  • 1




    Doesn't New Shepard use the BE-3, which is hydrolox? Did they test it with the BE-4?
    – DylanSp
    Nov 17 at 18:21













up vote
17
down vote



accepted







up vote
17
down vote



accepted






tl;dr: at an apparent magnitude of about +18.5 you need a several meter telescope and a dark sky. Hubble can do it too. So by reflected sunlight, definitely not by eye. The exhaust from a Methalox (CH4 + LOX) engine barely makes any light in the visible, so no help there.





Starting with the math from this answer:



I'm going to characterize the 55 x 9 meter white 2nd stage as a 22 meter diffuse sphere(ical cow) with albedo 0.3 for order of magnitude estimation.




The expression for absolute magnitude $M_{Abs}$ by rearranging the equation here is:



$$M_{Abs} = 5 left(log_{10}(1329) -frac{1}{2}log_{10}(text{albedo}) -log_{10}(D_{km})right)$$




For the "spherical cow" spacecraft that turns out to be an absolute magnitude of +25.




Knowing the absolute magnitude of an object, you calculate the apparent magnitude $m$ using:



$$ m = M_{Abs} + 2.5 log_{10}left(frac{d_{SR} d_{RE}}{1 text{AU}^2 O(1)}right), $$



where $d_{SR}$ and $d_{RE}$ are the Sun-Roadster and Roadster-Earth distances, each normalized by 1 AU, and the factor $O(1)$ is the phase integral, of order unity, taking into account the angular difference between the direction of illumination and the direction of viewing. In an order of magnitude calculation, this only becomes really significant when the body moves between the Sun and the viewer. See https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_System_bodies_(H).




In this case, replace Roadster with BFR. Since $d_{SR}$ and $d_{RE}$ are 1.0 and 0.0025 AU respectively, and ignoring the phase integral, the apparent magnitude is about -6.5 lower or +18.5 magnitude.



I think that can be seen with the Hubble Space Telescope above the atmosphere in a fairly short exposure. On the ground you'd need a several meter telescope and a dark night, but you can do it. If you want to use your eye, better find one of these telescopes that has an active eyepiece!



BFR's Raptor engines burn "methalox" (methane and liquid oxygen) CH4 + O2. The products are CO2 and H2O both gases. The brightness from the exhaust from many launches are from carbon soot glowing when kerosene (RP-1) is burned, not methane.





Here is a screenshot from the video Blue Origin BE-4 Engine Compilation during the daytime, so you can have a reference to brightness. I haven't found an outdoor firing of the Raptor yet:



Screenshot Blue Origin BE-4 Engine Compilation






share|improve this answer














tl;dr: at an apparent magnitude of about +18.5 you need a several meter telescope and a dark sky. Hubble can do it too. So by reflected sunlight, definitely not by eye. The exhaust from a Methalox (CH4 + LOX) engine barely makes any light in the visible, so no help there.





Starting with the math from this answer:



I'm going to characterize the 55 x 9 meter white 2nd stage as a 22 meter diffuse sphere(ical cow) with albedo 0.3 for order of magnitude estimation.




The expression for absolute magnitude $M_{Abs}$ by rearranging the equation here is:



$$M_{Abs} = 5 left(log_{10}(1329) -frac{1}{2}log_{10}(text{albedo}) -log_{10}(D_{km})right)$$




For the "spherical cow" spacecraft that turns out to be an absolute magnitude of +25.




Knowing the absolute magnitude of an object, you calculate the apparent magnitude $m$ using:



$$ m = M_{Abs} + 2.5 log_{10}left(frac{d_{SR} d_{RE}}{1 text{AU}^2 O(1)}right), $$



where $d_{SR}$ and $d_{RE}$ are the Sun-Roadster and Roadster-Earth distances, each normalized by 1 AU, and the factor $O(1)$ is the phase integral, of order unity, taking into account the angular difference between the direction of illumination and the direction of viewing. In an order of magnitude calculation, this only becomes really significant when the body moves between the Sun and the viewer. See https://en.wikipedia.org/wiki/Absolute_magnitude#Solar_System_bodies_(H).




In this case, replace Roadster with BFR. Since $d_{SR}$ and $d_{RE}$ are 1.0 and 0.0025 AU respectively, and ignoring the phase integral, the apparent magnitude is about -6.5 lower or +18.5 magnitude.



I think that can be seen with the Hubble Space Telescope above the atmosphere in a fairly short exposure. On the ground you'd need a several meter telescope and a dark night, but you can do it. If you want to use your eye, better find one of these telescopes that has an active eyepiece!



BFR's Raptor engines burn "methalox" (methane and liquid oxygen) CH4 + O2. The products are CO2 and H2O both gases. The brightness from the exhaust from many launches are from carbon soot glowing when kerosene (RP-1) is burned, not methane.





Here is a screenshot from the video Blue Origin BE-4 Engine Compilation during the daytime, so you can have a reference to brightness. I haven't found an outdoor firing of the Raptor yet:



Screenshot Blue Origin BE-4 Engine Compilation







share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 18 at 0:43

























answered Nov 17 at 12:15









uhoh

32.4k16112400




32.4k16112400








  • 1




    Thanks for the detailed answer, especially your addition about the engine chemistry! I'm not a native english speaker, but after I look up some of the physics vocabulary used I'll have a more in depth look on the formulas!
    – linusg
    Nov 17 at 12:47






  • 1




    Feel free to ask me to make something clearer here, or you can post a new question about the calculations after checking the links. Welcome to Space!
    – uhoh
    Nov 17 at 12:51








  • 2




    The shuttle main engines burned liquid hydrogen, not methane
    – matteol
    Nov 17 at 13:15










  • @matteol I knew something felt strange there, thanks!
    – uhoh
    Nov 17 at 13:18








  • 1




    Doesn't New Shepard use the BE-3, which is hydrolox? Did they test it with the BE-4?
    – DylanSp
    Nov 17 at 18:21














  • 1




    Thanks for the detailed answer, especially your addition about the engine chemistry! I'm not a native english speaker, but after I look up some of the physics vocabulary used I'll have a more in depth look on the formulas!
    – linusg
    Nov 17 at 12:47






  • 1




    Feel free to ask me to make something clearer here, or you can post a new question about the calculations after checking the links. Welcome to Space!
    – uhoh
    Nov 17 at 12:51








  • 2




    The shuttle main engines burned liquid hydrogen, not methane
    – matteol
    Nov 17 at 13:15










  • @matteol I knew something felt strange there, thanks!
    – uhoh
    Nov 17 at 13:18








  • 1




    Doesn't New Shepard use the BE-3, which is hydrolox? Did they test it with the BE-4?
    – DylanSp
    Nov 17 at 18:21








1




1




Thanks for the detailed answer, especially your addition about the engine chemistry! I'm not a native english speaker, but after I look up some of the physics vocabulary used I'll have a more in depth look on the formulas!
– linusg
Nov 17 at 12:47




Thanks for the detailed answer, especially your addition about the engine chemistry! I'm not a native english speaker, but after I look up some of the physics vocabulary used I'll have a more in depth look on the formulas!
– linusg
Nov 17 at 12:47




1




1




Feel free to ask me to make something clearer here, or you can post a new question about the calculations after checking the links. Welcome to Space!
– uhoh
Nov 17 at 12:51






Feel free to ask me to make something clearer here, or you can post a new question about the calculations after checking the links. Welcome to Space!
– uhoh
Nov 17 at 12:51






2




2




The shuttle main engines burned liquid hydrogen, not methane
– matteol
Nov 17 at 13:15




The shuttle main engines burned liquid hydrogen, not methane
– matteol
Nov 17 at 13:15












@matteol I knew something felt strange there, thanks!
– uhoh
Nov 17 at 13:18






@matteol I knew something felt strange there, thanks!
– uhoh
Nov 17 at 13:18






1




1




Doesn't New Shepard use the BE-3, which is hydrolox? Did they test it with the BE-4?
– DylanSp
Nov 17 at 18:21




Doesn't New Shepard use the BE-3, which is hydrolox? Did they test it with the BE-4?
– DylanSp
Nov 17 at 18:21










up vote
14
down vote













If you want an easy way to think about it, imagine how bright it might be in low Earth orbit, 240 miles up (which is just a bit lower than the International Space Station). However bright that is, it will be only a millionth as bright when it’s near the Moon, 240,000 miles away (and so a thousand times the distance). Is it likely that it will be bright enough in low orbit that you can still see it when it’s a millionth as bright as that?






share|improve this answer








New contributor




Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.


















  • Good one Mike. I figure you can "see a cellphone" from about 1/10th of a mile. So I said it would be like trying to see a cellphone at 100 miles. Sounds about right?
    – Fattie
    Nov 17 at 16:48










  • @Fattie It’s about right, but the crucial point is that something a thousand times further away isn’t a thousand times dimmer, it’s a million times dimmer. Inverse square law.
    – Mike Scott
    Nov 17 at 17:20






  • 5




    You got the same answer as I did with about a thousand times less work, congratulations! One million times dimmer is 15 magnitudes dimmer. Start with 3rd magnitude and add 15 and you get 18. +1
    – uhoh
    Nov 17 at 18:04






  • 4




    @linusg I think that this is a better answer than mine, because it's just as correct, but a lot more accessible.
    – uhoh
    Nov 17 at 18:06















up vote
14
down vote













If you want an easy way to think about it, imagine how bright it might be in low Earth orbit, 240 miles up (which is just a bit lower than the International Space Station). However bright that is, it will be only a millionth as bright when it’s near the Moon, 240,000 miles away (and so a thousand times the distance). Is it likely that it will be bright enough in low orbit that you can still see it when it’s a millionth as bright as that?






share|improve this answer








New contributor




Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.


















  • Good one Mike. I figure you can "see a cellphone" from about 1/10th of a mile. So I said it would be like trying to see a cellphone at 100 miles. Sounds about right?
    – Fattie
    Nov 17 at 16:48










  • @Fattie It’s about right, but the crucial point is that something a thousand times further away isn’t a thousand times dimmer, it’s a million times dimmer. Inverse square law.
    – Mike Scott
    Nov 17 at 17:20






  • 5




    You got the same answer as I did with about a thousand times less work, congratulations! One million times dimmer is 15 magnitudes dimmer. Start with 3rd magnitude and add 15 and you get 18. +1
    – uhoh
    Nov 17 at 18:04






  • 4




    @linusg I think that this is a better answer than mine, because it's just as correct, but a lot more accessible.
    – uhoh
    Nov 17 at 18:06













up vote
14
down vote










up vote
14
down vote









If you want an easy way to think about it, imagine how bright it might be in low Earth orbit, 240 miles up (which is just a bit lower than the International Space Station). However bright that is, it will be only a millionth as bright when it’s near the Moon, 240,000 miles away (and so a thousand times the distance). Is it likely that it will be bright enough in low orbit that you can still see it when it’s a millionth as bright as that?






share|improve this answer








New contributor




Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









If you want an easy way to think about it, imagine how bright it might be in low Earth orbit, 240 miles up (which is just a bit lower than the International Space Station). However bright that is, it will be only a millionth as bright when it’s near the Moon, 240,000 miles away (and so a thousand times the distance). Is it likely that it will be bright enough in low orbit that you can still see it when it’s a millionth as bright as that?







share|improve this answer








New contributor




Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|improve this answer



share|improve this answer






New contributor




Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









answered Nov 17 at 16:25









Mike Scott

24113




24113




New contributor




Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





New contributor





Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






Mike Scott is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.












  • Good one Mike. I figure you can "see a cellphone" from about 1/10th of a mile. So I said it would be like trying to see a cellphone at 100 miles. Sounds about right?
    – Fattie
    Nov 17 at 16:48










  • @Fattie It’s about right, but the crucial point is that something a thousand times further away isn’t a thousand times dimmer, it’s a million times dimmer. Inverse square law.
    – Mike Scott
    Nov 17 at 17:20






  • 5




    You got the same answer as I did with about a thousand times less work, congratulations! One million times dimmer is 15 magnitudes dimmer. Start with 3rd magnitude and add 15 and you get 18. +1
    – uhoh
    Nov 17 at 18:04






  • 4




    @linusg I think that this is a better answer than mine, because it's just as correct, but a lot more accessible.
    – uhoh
    Nov 17 at 18:06


















  • Good one Mike. I figure you can "see a cellphone" from about 1/10th of a mile. So I said it would be like trying to see a cellphone at 100 miles. Sounds about right?
    – Fattie
    Nov 17 at 16:48










  • @Fattie It’s about right, but the crucial point is that something a thousand times further away isn’t a thousand times dimmer, it’s a million times dimmer. Inverse square law.
    – Mike Scott
    Nov 17 at 17:20






  • 5




    You got the same answer as I did with about a thousand times less work, congratulations! One million times dimmer is 15 magnitudes dimmer. Start with 3rd magnitude and add 15 and you get 18. +1
    – uhoh
    Nov 17 at 18:04






  • 4




    @linusg I think that this is a better answer than mine, because it's just as correct, but a lot more accessible.
    – uhoh
    Nov 17 at 18:06
















Good one Mike. I figure you can "see a cellphone" from about 1/10th of a mile. So I said it would be like trying to see a cellphone at 100 miles. Sounds about right?
– Fattie
Nov 17 at 16:48




Good one Mike. I figure you can "see a cellphone" from about 1/10th of a mile. So I said it would be like trying to see a cellphone at 100 miles. Sounds about right?
– Fattie
Nov 17 at 16:48












@Fattie It’s about right, but the crucial point is that something a thousand times further away isn’t a thousand times dimmer, it’s a million times dimmer. Inverse square law.
– Mike Scott
Nov 17 at 17:20




@Fattie It’s about right, but the crucial point is that something a thousand times further away isn’t a thousand times dimmer, it’s a million times dimmer. Inverse square law.
– Mike Scott
Nov 17 at 17:20




5




5




You got the same answer as I did with about a thousand times less work, congratulations! One million times dimmer is 15 magnitudes dimmer. Start with 3rd magnitude and add 15 and you get 18. +1
– uhoh
Nov 17 at 18:04




You got the same answer as I did with about a thousand times less work, congratulations! One million times dimmer is 15 magnitudes dimmer. Start with 3rd magnitude and add 15 and you get 18. +1
– uhoh
Nov 17 at 18:04




4




4




@linusg I think that this is a better answer than mine, because it's just as correct, but a lot more accessible.
– uhoh
Nov 17 at 18:06




@linusg I think that this is a better answer than mine, because it's just as correct, but a lot more accessible.
– uhoh
Nov 17 at 18:06










up vote
4
down vote













Rocket engines burning in vacuum produce large exhaust plumes that rapidly spread outward to 'fill' the vacuum. This means that for a distance of many dozens of meters - or more - they produce a visible cloud of gas that can catch sunlight and produce very large, visible artifacts in a clear night sky. So - engine burns near Earth (departure, or arrivals burning into orbit) will be quite easily visible to those who are in night and under the burns.



For example, this GLONASS launch trail taken from a thread full of rocket plume images. GLONASS launch trail



Mid course burns may be visible as well, though much less dramatic. Arrival and departure burns happening in the vicinity of the moon are not likely to be visible at all to the naked eye due to great distance.






share|improve this answer

















  • 2




    I am not sure that CO2 + H2O exhaust in vacuum would ever form a visible plume. Without a buffer gas (i.e. low pressure atmosphere) to slow it quickly, wouldn't the molecules expand to large separation distances and have no chance to recombine into droplets?
    – uhoh
    Nov 18 at 2:00






  • 1




    I can't find suitable evidence for my hunch they will remain visible. Gaseous nitrogen thrusters produce visible plumes. Fuel dumps are visible, though that contains liquid fuel. I believe water vapor will produce visible ice crystals, but this is just my hunch.
    – Saiboogu
    Nov 18 at 15:26






  • 1




    @uhoh Wouldn't they flash-freeze into tiny crystals with pressure drop in vacuum?
    – Eth
    2 days ago










  • @Eth It's a race. If the molecules bump into each other frequently enough, they can stick and start forming particles, but if their relative velocity moves them far enough apart fast enough so that collisions are infrequent, then they won't. They won't slow down in vacuum. Watch launch videos and especially the views behind 2nd stages where you see the red-hot nozzle and the path back to Earth, RP-1/LOX engines don't seem to leave any trail behind themselves at all, and that's very similar chemistry to methalox.
    – uhoh
    2 days ago










  • RP-1/LOX engines don't produce a plume visible from the vehicle's POV, but they produce plumes that are exceptionally visible when lit by sunlight against a dark sky (see any SpaceX sunset/sunrise launch).
    – Saiboogu
    yesterday

















up vote
4
down vote













Rocket engines burning in vacuum produce large exhaust plumes that rapidly spread outward to 'fill' the vacuum. This means that for a distance of many dozens of meters - or more - they produce a visible cloud of gas that can catch sunlight and produce very large, visible artifacts in a clear night sky. So - engine burns near Earth (departure, or arrivals burning into orbit) will be quite easily visible to those who are in night and under the burns.



For example, this GLONASS launch trail taken from a thread full of rocket plume images. GLONASS launch trail



Mid course burns may be visible as well, though much less dramatic. Arrival and departure burns happening in the vicinity of the moon are not likely to be visible at all to the naked eye due to great distance.






share|improve this answer

















  • 2




    I am not sure that CO2 + H2O exhaust in vacuum would ever form a visible plume. Without a buffer gas (i.e. low pressure atmosphere) to slow it quickly, wouldn't the molecules expand to large separation distances and have no chance to recombine into droplets?
    – uhoh
    Nov 18 at 2:00






  • 1




    I can't find suitable evidence for my hunch they will remain visible. Gaseous nitrogen thrusters produce visible plumes. Fuel dumps are visible, though that contains liquid fuel. I believe water vapor will produce visible ice crystals, but this is just my hunch.
    – Saiboogu
    Nov 18 at 15:26






  • 1




    @uhoh Wouldn't they flash-freeze into tiny crystals with pressure drop in vacuum?
    – Eth
    2 days ago










  • @Eth It's a race. If the molecules bump into each other frequently enough, they can stick and start forming particles, but if their relative velocity moves them far enough apart fast enough so that collisions are infrequent, then they won't. They won't slow down in vacuum. Watch launch videos and especially the views behind 2nd stages where you see the red-hot nozzle and the path back to Earth, RP-1/LOX engines don't seem to leave any trail behind themselves at all, and that's very similar chemistry to methalox.
    – uhoh
    2 days ago










  • RP-1/LOX engines don't produce a plume visible from the vehicle's POV, but they produce plumes that are exceptionally visible when lit by sunlight against a dark sky (see any SpaceX sunset/sunrise launch).
    – Saiboogu
    yesterday















up vote
4
down vote










up vote
4
down vote









Rocket engines burning in vacuum produce large exhaust plumes that rapidly spread outward to 'fill' the vacuum. This means that for a distance of many dozens of meters - or more - they produce a visible cloud of gas that can catch sunlight and produce very large, visible artifacts in a clear night sky. So - engine burns near Earth (departure, or arrivals burning into orbit) will be quite easily visible to those who are in night and under the burns.



For example, this GLONASS launch trail taken from a thread full of rocket plume images. GLONASS launch trail



Mid course burns may be visible as well, though much less dramatic. Arrival and departure burns happening in the vicinity of the moon are not likely to be visible at all to the naked eye due to great distance.






share|improve this answer












Rocket engines burning in vacuum produce large exhaust plumes that rapidly spread outward to 'fill' the vacuum. This means that for a distance of many dozens of meters - or more - they produce a visible cloud of gas that can catch sunlight and produce very large, visible artifacts in a clear night sky. So - engine burns near Earth (departure, or arrivals burning into orbit) will be quite easily visible to those who are in night and under the burns.



For example, this GLONASS launch trail taken from a thread full of rocket plume images. GLONASS launch trail



Mid course burns may be visible as well, though much less dramatic. Arrival and departure burns happening in the vicinity of the moon are not likely to be visible at all to the naked eye due to great distance.







share|improve this answer












share|improve this answer



share|improve this answer










answered Nov 17 at 18:39









Saiboogu

3,4021627




3,4021627








  • 2




    I am not sure that CO2 + H2O exhaust in vacuum would ever form a visible plume. Without a buffer gas (i.e. low pressure atmosphere) to slow it quickly, wouldn't the molecules expand to large separation distances and have no chance to recombine into droplets?
    – uhoh
    Nov 18 at 2:00






  • 1




    I can't find suitable evidence for my hunch they will remain visible. Gaseous nitrogen thrusters produce visible plumes. Fuel dumps are visible, though that contains liquid fuel. I believe water vapor will produce visible ice crystals, but this is just my hunch.
    – Saiboogu
    Nov 18 at 15:26






  • 1




    @uhoh Wouldn't they flash-freeze into tiny crystals with pressure drop in vacuum?
    – Eth
    2 days ago










  • @Eth It's a race. If the molecules bump into each other frequently enough, they can stick and start forming particles, but if their relative velocity moves them far enough apart fast enough so that collisions are infrequent, then they won't. They won't slow down in vacuum. Watch launch videos and especially the views behind 2nd stages where you see the red-hot nozzle and the path back to Earth, RP-1/LOX engines don't seem to leave any trail behind themselves at all, and that's very similar chemistry to methalox.
    – uhoh
    2 days ago










  • RP-1/LOX engines don't produce a plume visible from the vehicle's POV, but they produce plumes that are exceptionally visible when lit by sunlight against a dark sky (see any SpaceX sunset/sunrise launch).
    – Saiboogu
    yesterday
















  • 2




    I am not sure that CO2 + H2O exhaust in vacuum would ever form a visible plume. Without a buffer gas (i.e. low pressure atmosphere) to slow it quickly, wouldn't the molecules expand to large separation distances and have no chance to recombine into droplets?
    – uhoh
    Nov 18 at 2:00






  • 1




    I can't find suitable evidence for my hunch they will remain visible. Gaseous nitrogen thrusters produce visible plumes. Fuel dumps are visible, though that contains liquid fuel. I believe water vapor will produce visible ice crystals, but this is just my hunch.
    – Saiboogu
    Nov 18 at 15:26






  • 1




    @uhoh Wouldn't they flash-freeze into tiny crystals with pressure drop in vacuum?
    – Eth
    2 days ago










  • @Eth It's a race. If the molecules bump into each other frequently enough, they can stick and start forming particles, but if their relative velocity moves them far enough apart fast enough so that collisions are infrequent, then they won't. They won't slow down in vacuum. Watch launch videos and especially the views behind 2nd stages where you see the red-hot nozzle and the path back to Earth, RP-1/LOX engines don't seem to leave any trail behind themselves at all, and that's very similar chemistry to methalox.
    – uhoh
    2 days ago










  • RP-1/LOX engines don't produce a plume visible from the vehicle's POV, but they produce plumes that are exceptionally visible when lit by sunlight against a dark sky (see any SpaceX sunset/sunrise launch).
    – Saiboogu
    yesterday










2




2




I am not sure that CO2 + H2O exhaust in vacuum would ever form a visible plume. Without a buffer gas (i.e. low pressure atmosphere) to slow it quickly, wouldn't the molecules expand to large separation distances and have no chance to recombine into droplets?
– uhoh
Nov 18 at 2:00




I am not sure that CO2 + H2O exhaust in vacuum would ever form a visible plume. Without a buffer gas (i.e. low pressure atmosphere) to slow it quickly, wouldn't the molecules expand to large separation distances and have no chance to recombine into droplets?
– uhoh
Nov 18 at 2:00




1




1




I can't find suitable evidence for my hunch they will remain visible. Gaseous nitrogen thrusters produce visible plumes. Fuel dumps are visible, though that contains liquid fuel. I believe water vapor will produce visible ice crystals, but this is just my hunch.
– Saiboogu
Nov 18 at 15:26




I can't find suitable evidence for my hunch they will remain visible. Gaseous nitrogen thrusters produce visible plumes. Fuel dumps are visible, though that contains liquid fuel. I believe water vapor will produce visible ice crystals, but this is just my hunch.
– Saiboogu
Nov 18 at 15:26




1




1




@uhoh Wouldn't they flash-freeze into tiny crystals with pressure drop in vacuum?
– Eth
2 days ago




@uhoh Wouldn't they flash-freeze into tiny crystals with pressure drop in vacuum?
– Eth
2 days ago












@Eth It's a race. If the molecules bump into each other frequently enough, they can stick and start forming particles, but if their relative velocity moves them far enough apart fast enough so that collisions are infrequent, then they won't. They won't slow down in vacuum. Watch launch videos and especially the views behind 2nd stages where you see the red-hot nozzle and the path back to Earth, RP-1/LOX engines don't seem to leave any trail behind themselves at all, and that's very similar chemistry to methalox.
– uhoh
2 days ago




@Eth It's a race. If the molecules bump into each other frequently enough, they can stick and start forming particles, but if their relative velocity moves them far enough apart fast enough so that collisions are infrequent, then they won't. They won't slow down in vacuum. Watch launch videos and especially the views behind 2nd stages where you see the red-hot nozzle and the path back to Earth, RP-1/LOX engines don't seem to leave any trail behind themselves at all, and that's very similar chemistry to methalox.
– uhoh
2 days ago












RP-1/LOX engines don't produce a plume visible from the vehicle's POV, but they produce plumes that are exceptionally visible when lit by sunlight against a dark sky (see any SpaceX sunset/sunrise launch).
– Saiboogu
yesterday






RP-1/LOX engines don't produce a plume visible from the vehicle's POV, but they produce plumes that are exceptionally visible when lit by sunlight against a dark sky (see any SpaceX sunset/sunrise launch).
– Saiboogu
yesterday












linusg is a new contributor. Be nice, and check out our Code of Conduct.










 

draft saved


draft discarded


















linusg is a new contributor. Be nice, and check out our Code of Conduct.













linusg is a new contributor. Be nice, and check out our Code of Conduct.












linusg is a new contributor. Be nice, and check out our Code of Conduct.















 


draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fspace.stackexchange.com%2fquestions%2f32064%2fwill-it-be-possible-to-see-bfr-approaching-the-moon-from-earth-with-naked-eye%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

AnyDesk - Fatal Program Failure

How to calibrate 16:9 built-in touch-screen to a 4:3 resolution?

QoS: MAC-Priority for clients behind a repeater