Saturn V questions

[Glom]

1. How big would the IU be if was built using today's computing technology?
2. Did the Saturn V put the spacecraft into EPO in a single burn?
3. Has anyone else noticed the difference between the yellow smokey flame of the F1 and the colourless flame of J2?

[korjik]

F1 used kerosene, the j2s used liquid hydrogen, IIRC

[Glom]

F1 used kerosene, the j2s used liquid hydrogen, IIRC

Yes, indeed. I was commenting more than questioning. I guess the method behind that madness is being discussed in that thread about solid fuel versus liquid fuel.

[korjik]

technically, both are liquid fuels

[cjl]

Yes, but it's a similar compromise - the LH₂ has a higher Isp and a lower density than RP-1. Solids are even more dense and less efficient than RP-1.

[astromark]

1. How big would the IU be if was built using today's computing technology?
2. Did the Saturn V put the spacecraft into EPO in a single burn?
3. Has anyone else noticed the difference between the yellow smokey flame of the F1 and the colourless flame of J2?

. . . You might just as well talk in Swahili... Those of you that spend some hours talking of lunar orbital trajectories might understand this.,
I am struggling. What is EPO ?...
What is IU ?... I can not be the only person here that wanted to know.... ?
If I understand you ( and there's doubt. ) Then No. The Saturn 5 had stages. Without stage two. It would be coming down. Before reaching orbital Velocity... and yes the space craft if built today, could be smaller and lighter. 40 years of Microsoft, lol

[kucharek]

1. How big would the IU be if was built using today's computing technology?
2. Did the Saturn V put the spacecraft into EPO in a single burn?
3. Has anyone else noticed the difference between the yellow smokey flame of the F1 and the colourless flame of J2?

1. Don't know the size of the avionics compartment of a heavy lift booster. Also keep in mind, that the structure of the IU was largely empty. More some kind of interstage ring with plenty of equipment fixed to its wall.
2. For the Apollo stack, there was also a short burn of the 3rd stage, the S-IVB necessary to reach earth orbit. The S-IVB was later restarted for TLI. To get Skylab into orbit - with Skylab basically being an empty S-IVB - only two stages of the Saturn V were necessary.
3. Candle- vs gaslight

[kucharek]

I am struggling. What is EPO ?...

You missed years of doping debates, it seems
Don't mind. Here we talk about Earth Parking Orbit

What is IU ?

Instrument Unit. The part of the Saturn V which contained the avionics. A ring struccture on top the 3rd stage.
http://en.wikipedia.org/wiki/Saturn_V_Instrument_Unit

[Eta C]

Should you find yourself in the DC area I recommend visiting the Smithsonian Air & Space Museum's second site at the Udvar-Hazy center near Dulles Airport. In the space gallery (besides the Shuttle test vehicle Enterprise) they have the instrumentation unit of a Saturn V on display. Lots of wiring. Besides the avionics computers it had the gyros for the rocket itself. These days, instead of a physical gyro they probably use laser ring gyros. More accurate, lighter, and smaller.

P.S. Of course, the main A&S Museum on the DC Mall should be a pilgramage site for any aerospace geek. The Apollo 11 capsule, Friendship 7, Gemini IV, Spirit of St. Louis, Glamourous Glennis, an X-15, and that's just the entrance gallery. The Wright Flyer used to be there, but it's now in its own special gallery.

[matthewota]

The Instrument Unit, if built today, would be the same diameter and roughly the same height. The electronics boxes would be smaller, though.

[astromark]

Under this heading of The Saturn Five Assembly could this be an aside issue of interest ?
The whole conception of the re-usable vehicle was to reduce costs. ?
The Saturn 5 must have cost a disproportional amount. Yes I understand that the Shuttle program has been expensive. That has been a result of compromises. I believe. I seem to recall the original shuttle was to be bigger or, have I been duped...

[kucharek]

Under this heading of The Saturn Five Assembly could this be an aside issue of interest ?
The whole conception of the re-usable vehicle was to reduce costs. ?
The Saturn 5 must have cost a disproportional amount. Yes I understand that the Shuttle program has been expensive. That has been a result of compromises. I believe. I seem to recall the original shuttle was to be bigger or, have I been duped...

Smaller with smaller wings. The Air Force wanted to be able to launch and return *big* stuff and they wanted to be able to return to launch site after one orbit, which made it necessary to add big wings so the shuttle could steer sideways a long way on the reentry flight.

[Jason Thompson]

[LIST=1][*]How big would the IU be if was built using today's computing technology?

Probably about the same size. Its structural size was determined more by requirements of space to fit the LM than the size of the electronics components being put in it. There's a lot of free space inside the IU. If you look at the early concept drawings of the Saturn V (before they knew how big the LM would be), the IU was going to be much the same as on the Saturn I, the same diameter as the service module.

[*]Did the Saturn V put the spacecraft into EPO in a single burn?

The Saturn V used up the first two stages and a bit of the third to reach parking orbit. It then used the rest of the fuel in the third stage for TLI.

[*]Has anyone else noticed the difference between the yellow smokey flame of the F1 and the colourless flame of J2?

A result of the F1 running on kerosene while the J2 ran on liquid hydrogen. Liquid hydrogen was not a fuel of choice for first stage engines for two reasons. One was the general discomfort surrounding lighting an LH2 engine on the ground at the time, and the other was the fact that the first stage would have had to be so much bigger due to the much lower density of liquid hydrogen compared to kerosene.

[Glom]

Thanks for your answers.

With regard to the burn to get into orbit, what I'm asking is at SECO, as the spacecraft in a sustainable orbit or did it need to circularise like the Space Shuttle does after burn out.

[NEOWatcher]

With regard to the burn to get into orbit, what I'm asking is at SECO, as the spacecraft in a sustainable orbit or did it need to circularise like the Space Shuttle does after burn out.

At second stage burn out, the Sat-V was only traveling a bit over 15k mph. Not enough for orbit.

[Hornblower]

Thanks for your answers.

With regard to the burn to get into orbit, what I'm asking is at SECO, as the spacecraft in a sustainable orbit or did it need to circularise like the Space Shuttle does after burn out.

It was in a sustainable orbit, at least for a few hours, from the moment of SECO. That occurred at a higher altitude than that of the main engine shutdown of the shuttle.

[NEOWatcher]

It was in a sustainable orbit, at least for a few hours, from the moment of SECO. That occurred at a higher altitude than that of the main engine shutdown of the shuttle.

Altitude means nothing without the speed.
If you last one orbit, you're going to stay up quite a bit longer than a few hours.

[Hornblower]

Altitude means nothing without the speed.
If you last one orbit, you're going to stay up quite a bit longer than a few hours.

Altitude means everything when considering the atmospheric drag. Atmospheric density decreases by roughly a factor of 10 for each increase of 10 miles in altitude. If your initial orbit is too low, you might complete one orbit with a slight loss of altitude from the air drag, then a second orbit with considerably more descent in increasing drag, and then the final reentry plunge part way through a third orbit. If we make the initial orbit just a few miles higher, we might complete many more orbits before the final plunge.

[Peter B]

Thanks for your answers.

With regard to the burn to get into orbit, what I'm asking is at SECO, as the spacecraft in a sustainable orbit or did it need to circularise like the Space Shuttle does after burn out.

There was no need for a circularisation burn. The spacecraft was in a roughly circular orbit, but it was very low - for Apollo 15 it was about 170 kilometres up. As a result, although it was in orbit, it wouldn't have remained in orbit very long if it hadn't gone to the Moon, due to atmospheric drag.

[NEOWatcher]

Altitude means everything when considering the atmospheric drag.

I think we are arguing apples and oranges here.
You are right that the atmospheric effects need to be overcome, but you do need sufficient speed for your orbit to "miss" the atmosphere or Earth at perigee.

Now; if someone can point out how 15300 mph can do that, or point out the fact that I got the wrong reference for the speed at SECO, then I'll re-think that.

[schlaugh]

SECO = Single Engine Cutoff; i.e. shutdown of the S-IVB's single J2 engine after achieving a relatively low circular orbit after ~12 mins 30 secs into powered ascent.

From the Smithsonian:

Third Stage (S-IVB): The third stage contains one J-2 engine. This engine burns for 2.75 minutes boosting the spacecraft to orbital velocity of about 17,500 mph. The third stage is shut down with fuel remaining and remains attached the spacecraft in Earth orbit. The J-2 engine is reignited to propel the spacecraft into translunar trajectory (speed of 24,500 mph) before finally being discarded.

And a chart showing specific altitude and speed parameters for Apollo 11 (although I can't verify if these are actual or theoretical).

[KaiYeves]

Should you find yourself in the DC area I recommend visiting the Smithsonian Air & Space Museum's second site at the Udvar-Hazy center near Dulles Airport. In the space gallery (besides the Shuttle test vehicle Enterprise) they have the instrumentation unit of a Saturn V on display. Lots of wiring. Besides the avionics computers it had the gyros for the rocket itself. These days, instead of a physical gyro they probably use laser ring gyros. More accurate, lighter, and smaller.

P.S. Of course, the main A&S Museum on the DC Mall should be a pilgramage site for any aerospace geek. The Apollo 11 capsule, Friendship 7, Gemini IV, Spirit of St. Louis, Glamourous Glennis, an X-15, and that's just the entrance gallery. The Wright Flyer used to be there, but it's now in its own special gallery.

Yes, definitely visit the Air and Space Museum. I went crazy just running around and blabbing to myself about all the different exhibits. You may do the same. (But you probably won't have a disapproving teacher watching you while you do it.)

[NEOWatcher]

SECO = Single Engine Cutoff

Ouch, that might explain some of my confusion.
Just don't ask my why I was thinking Second Engine Cutoff.

[kucharek]

Ouch, that might explain some of my confusion.
Just don't ask my why I was thinking Second Engine Cutoff.

I know it as standing for Sustainer Engine Cut Off

[schlaugh]

I know it as standing for Sustainer Engine Cut Off

Ahhh...you are correct. My recollection / assumption was wrong although in the case of the S-IVB, the net result is the same; i.e. one sustaining engine that shuts off after achieving orbit.

Found this definition at NASA:

A rocket engine that stays with a spacecraft during ascent after one or more booster engines have dropped off. It sustains or steadily increases the spacecraft's speed during ascent. The term is also applied to a rocket engine used on an orbital flider [sic] to provide the small amount of thrust now and then required to compensate for the drag imparted by air particles in the upper atmosphere.

[mugaliens]

I think the Shuttle modus operandi was to bend over backwards trying to achieve orbit, and if that failed, abort to a recoverable runway, of which dozens are carved out all over the planet.