Could A Space Shuttle Get To The Moon?

[Janus]

2 hours ago, Sensei said:

..and so what? It's a one-way mission anyway, because of what I said earlier. It will melt down..

 

Oxygen can be (and is) regenerated from CO₂, which is exhaled. "Half" of the Apollo 13 movie is about how to make CO₂ filters. You can have CO₂ to O₂ converters built into the suit.

An interesting option for scuba divers in emergency situations.

 

Halc's original statement dealt with the difficulty of even putting a craft into orbit "near" the Sun.

Let's take the Parker Solar probe, on its closest approach it is ~7 million km from the Sun in a highly elliptical orbit.  This took several orbits and 7 gravitational assists from Venus to achieve.

But let's look at its first perihelion, which was at ~22 million km.  What would it have taken to circularize the orbit at that distance? A delta V of ~ 56.6 km/sec.  This is 5 times the escape velocity from Earth's surface.   Now, given a typical launch vehicle engine, it would take  roughly 11 kg of fuel for every kg of payload to reach escape velocity. For 56.6 km/sec, that jumps to 232245 kg per kg of payload. 

 

[John Cuthber]

6 hours ago, Sensei said:

and so what?

And so it won't end up  in orbit round the sun.

Had  you forgotten what you were replying to?

 

On 10/10/2023 at 7:41 PM, Halc said:

Similar reasoning shows why it is so much easier to escape the solar system from Earth's orbit than it is to drop an object into the sun, let alone actually go into low orbit around it, which is currently beyond our technological limits.

 

 

6 hours ago, Sensei said:

Oxygen can be (and is) regenerated from CO₂, which is exhaled. "Half" of the Apollo 13 movie is about how to make CO₂ filters. You can have CO₂ to O₂ converters built into the suit.

That's a convenient way to carry oxygen; but not a lightweight option.
 

 

6 hours ago, Sensei said:

An interesting option for scuba divers in emergency situations.

Why wait for an emergency?
One of these will scrub out the CO2.
https://en.wikipedia.org/wiki/Rebreather_diving

But they aren't easy to work with.
These are even more scary.
https://en.wikipedia.org/wiki/Potassium_superoxide#Applications


And we know what happens if you mess up an oxygen generator of that sort in water.

"Analysts concluded that 23 sailors took refuge in the small ninth compartment and survived for more than six hours. When oxygen ran low, they attempted to replace a potassium superoxide chemical oxygen cartridge, but it fell into the oily sea water and exploded on contact. The resulting fire killed several crew members and triggered a flash fire that consumed the remaining oxygen, suffocating the remaining survivors."
from
https://en.wikipedia.org/wiki/Kursk_submarine_disaster

[Sensei]

10 minutes ago, John Cuthber said:

And so it won't end up  in orbit round the sun.

Had  you forgotten what you were replying to?

Do you read what you quote?

 

On 10/10/2023 at 8:41 PM, Halc said:

Similar reasoning shows why it is so much easier to escape the solar system from Earth's orbit than it is to drop an object into the sun, let alone actually go into low orbit around it, which is currently beyond our technological limits.

[John Cuthber]

25 minutes ago, Sensei said:

Do you read what you quote?

Yes
 

 

26 minutes ago, Sensei said:

let alone actually go into low orbit around it,

 

[Sensei]

1 minute ago, John Cuthber said:

 

27 minutes ago, Sensei said:

let alone actually go into low orbit around it,

Learn to quote correctly, because I didn't say that..

 

[John Cuthber]

Tell the site software.
You did, in fact, say it.
You were quoting Halc.
 

[Sensei]

  

18 minutes ago, John Cuthber said:

Yes

When someone says A and B, and A refutes your claims and B confirms them, you brazenly ignore what is in A, when you clearly have it on the front of your screen, as if it wasn't said at all. This is acting in bad faith. That is, as usual. Grow up some day.

12 minutes ago, John Cuthber said:

You were quoting Halc.

..I have highlighted in bold what I was referring to ("A").. maybe your site's software does not work in this area as well..

 

13 minutes ago, John Cuthber said:

Tell the site software.

 

I could teach you how to properly quote a person who is quoting someone else. You need to use the mouse and select the area, not just the message, but start from the first gray bar, and then press ctrl-c and ctrl-v in your answer. Verify the author.

 

See:

15 minutes ago, John Cuthber said:

You were quoting Halc.

 

If you try to do this with the quote button in the toolbox, you will end up with the wrong author of the quote..

 

Edited October 12, 2023 by Sensei

[John Cuthber]

Here's what you said, and what you said it in response to.
 

You asked what does it have to do with escape velocity and I explained why part of it has something to do with escape velocity.
I said "The escape velocity isn't strictly relevant, but it's a proxy for gravitational energy."

On 10/11/2023 at 10:54 AM, John Cuthber said:

The escape velocity isn't strictly relevant, but it's a proxy for gravitational energy.
Essentially you "drop" your spacecraft towards the sun and it accelerates as it goes.
If you don't fire retro rockets to slow it down, it hits the sun.
It takes pretty much as much fuel to get something "down" as it does "up".

And you ignored that and focussed on this bit.
"If you don't fire retro rockets to slow it down, it hits the sun."
 

8 hours ago, Sensei said:

.and so what? It's a one-way mission anyway, because of what I said earlier. It will melt down..

Repeating your unproven assertion that you can't put something in orbit near the sun- well, in reality it depends in how near you get- but that's beside the point.

But the answer to "so what?" is still that  escape velocity- or gravitational potential energy- is important to the idea of putting something in orbit round the  sun (As Halc said)- even if the thing melts.



 

1 hour ago, Sensei said:

When someone says A and B, and A refutes your claims and B confirms them, you brazenly ignore what is in A

You brazenly  ignored part of what Halc said and bolded part of it, didn't you?
 

[paulsutton]

On 10/12/2023 at 12:07 AM, Janus said:

The mass of the oxygen used per person for a trip to the Moon and back is pretty insignificant. compared to the mass of the person themselves. The real savings in not sending a person is in the mass of the person themselves, not in the oxygen they would use.

Ah ok, no problem, 

[Photon Guy]

On 10/10/2023 at 4:15 AM, Eise said:

It couldn't. Orbiting earth means that the space shuttle did not escape earth's gravity. Why else would it keep in its orbit? Apollo could travel to the point where the gravitation of the earth and moon exactly cancel. Getting over that point means that it 'falls' to the moon. But the moon itself neither escapes earth's gravity, otherwise it would fly away. Escaping earth's gravity for space vehicles means that gravity fields of other objects (planets, moon, sun, ...) have (much) more impact than the gravity field of the earth. 

All you have to do is build a spacecraft that can achieve escape velocity. Once you reach escape velocity you're guaranteed to not fall back to the Earth, regardless of the gravitational effect of other objects such as the moon. That's how probes such as Voyager work.  

[Eise]

6 hours ago, Photon Guy said:

All you have to do is build a spacecraft that can achieve escape velocity. Once you reach escape velocity you're guaranteed to not fall back to the Earth, regardless of the gravitational effect of other objects such as the moon. That's how probes such as Voyager work.  

Yes, thanks for the explanation, I really needed that .

Your OP was about the Space Shuttle. It was not able to reach escape velocity. And for reaching the moon one does not need the 'full escape velocity': reaching the point where the gravitation of earth an moon exactly cancel is enough. But then, for the return trip, you still need fuel to reach that point again, against the gravity of the moon.

[Photon Guy]

5 hours ago, Eise said:

Yes, thanks for the explanation, I really needed that .

Your OP was about the Space Shuttle. It was not able to reach escape velocity. And for reaching the moon one does not need the 'full escape velocity': reaching the point where the gravitation of earth an moon exactly cancel is enough. But then, for the return trip, you still need fuel to reach that point again, against the gravity of the moon.

But we have built spacecraft that do achieve escape velocity. I don't see why the shuttle couldn't do that considering the fact it could reach altitudes where Earth's escape velocity is very low. As for leaving the moon, the moon's gravity is much weaker than Earth's so it would take far less fuel. And you could just put the shuttle in orbit around the moon and use a lander to get to the moon's surface the way they did with the Saturn V rockets. 

[TheVat]

52 minutes ago, Photon Guy said:

But we have built spacecraft that do achieve escape velocity. I don't see why the shuttle couldn't do that considering the fact it could reach altitudes where Earth's escape velocity is very low

The problem is that the chemical propellant in the shuttle can't create the specific impulse required.  The mass of fuel it can hold won't be sufficient for a lunar trip.

Specific impulse is the change in momentum per unit mass for rocket fuels.  It hasn't increased much in the past few decades.

 

[Janus]

1 hour ago, Photon Guy said:

But we have built spacecraft that do achieve escape velocity. I don't see why the shuttle couldn't do that considering the fact it could reach altitudes where Earth's escape velocity is very low. As for leaving the moon, the moon's gravity is much weaker than Earth's so it would take far less fuel. And you could just put the shuttle in orbit around the moon and use a lander to get to the moon's surface the way they did with the Saturn V rockets. 

In order to reach LEO, a fully loaded shuttle needs all the fuel in that large external tank, plus two solid fuel boosters.

As I pointed out in an earlier post, you need about 2.2 km/sec of delta v to enter a trans-lunar orbit from LEO.  Even if the entirety of the cargo capacity of the shuttle was extra fuel, the SSME's wouldn't be capable of getting the shuttle up to this speed.

Once at the Moon, your shuttle would be moving ~ 0.8 km/sec slower than the Moon, and would need to do another burn in order to be able match speeds and enter orbit around it.

Then to return, another burn is needed to re-enter another trans-lunar orbit in order to get back to Earth.  Once back, the shuttle will be moving at ~2.2 km/sec more than LEO orbital speed.  The shuttle can't hit the atmosphere at this speed, so it will need to do another burn to shed enough for re-entry.

So, this works out to at least 6 km/sec total delta v for the trip.  This jumps the fuel requirements to 2.8 times the mass of the empty shuttle. Adding a lander would increase this fuel requirement. (some thing the equivalent of the Apollo LEM, would require ~20% more fuel.

A good part of the Shuttle's mass is there for re-entry and landing, and would be dead weight as far as the majority of the trip is concerned, so you'd be burning a lot of fuel to get something to the Moon that is of no use when you get there.

[Photon Guy]

2 hours ago, Janus said:

In order to reach LEO, a fully loaded shuttle needs all the fuel in that large external tank, plus two solid fuel boosters.

As I pointed out in an earlier post, you need about 2.2 km/sec of delta v to enter a trans-lunar orbit from LEO.  Even if the entirety of the cargo capacity of the shuttle was extra fuel, the SSME's wouldn't be capable of getting the shuttle up to this speed.

Once at the Moon, your shuttle would be moving ~ 0.8 km/sec slower than the Moon, and would need to do another burn in order to be able match speeds and enter orbit around it.

Then to return, another burn is needed to re-enter another trans-lunar orbit in order to get back to Earth.  Once back, the shuttle will be moving at ~2.2 km/sec more than LEO orbital speed.  The shuttle can't hit the atmosphere at this speed, so it will need to do another burn to shed enough for re-entry.

So, this works out to at least 6 km/sec total delta v for the trip.  This jumps the fuel requirements to 2.8 times the mass of the empty shuttle. Adding a lander would increase this fuel requirement. (some thing the equivalent of the Apollo LEM, would require ~20% more fuel.

A good part of the Shuttle's mass is there for re-entry and landing, and would be dead weight as far as the majority of the trip is concerned, so you'd be burning a lot of fuel to get something to the Moon that is of no use when you get there.

Well then I would say it's a good thing we retired the shuttle. We're better off using rockets such as Atlas V that we used to get the Curiosity rover to Mars. 

[zapatos]

4 minutes ago, Photon Guy said:

Well then I would say it's a good thing we retired the shuttle.

The shuttle was not retired because it could not go to the moon. It was never intended to go to the moon. If it hadn't been retired no one would even have considered rehabbing it to go to the moon. I'm not sure why you are having such a difficult time with this.

[StringJunky]

Everything is designed for the particular mission, dealing with the various Delta V's (velocity changes) in that mission. Lot's of Delta V's means lots of fuel, as Janus points out.

Edited October 30, 2023 by StringJunky

[Photon Guy]

On 10/30/2023 at 2:54 PM, zapatos said:

 I'm not sure why you are having such a difficult time with this.

Im not having a difficult time.