Space Voyage #1

[TheBigDog]

Via ground-based RADAR (real world: via the gravity simulator I used in another thread, slightly enhanced to support propulsion), I made The Prophesy passing the orbit of the Moon like a bat out of hell at an distance above Earth of 400130988 m, velocity 12789.2 m/s, at about 1441 EST. Max velocity 13049.6 m/s at DAE 91429242 m was at 0800 EST, at engine cutoff, following her 3.5 hr, .98 m.s^2 burn. Pre-burn low earth orbital velocity was 7690 m/s at DAE 400000 m.

 

I’m a little perplexed, as I’d heard she intended to orbit the Moon, but apparently she’d decided to stretch her legs a bit. Wow. :D

What should our orbital velocity around the moon be?

 

Bill

[arkain101]

Also I just got half life, so when you have a map sorta ready I would like to try it

 

ALrighty! I will hammer down and make'er shine.

[TheFaithfulStone]

Being the Mac-user on board - I have not half-life. Nor shall I be getting it.

 

Someone really oughta crack open those cargo containers and make sure we don't have a stowaway.

 

What should our orbital velocity around the moon be?

 

I've been trying to find a gravity calculator for the Mac so I could plot us one of those nifty "slingshot around everything" courses through the solar system, and figure this out as well. UNFORTUNATELY, I have been unable to locate such a beast outside of the Orbiter Space Sim, which, as I mentioned before, I can't run, lacking a PC.

 

TFS

[TheBigDog]

If you want to know how the pros did it back in the day, here is a great site that shows how it was done. Craig is right. I am going to revise our burn time by quite a bit.

 

In our earth orbit at 400 km altitude we were traveling at 7.67 km/s. Escape velocity is 11.2 km/s. At an accelleration rate of .1g, we would need to burn the engines for roughly one hour to change our speed by 3.53 km/s at a rate of .98m/s/s.

 

This one hour burn set us on our course for the moon. As we coast toward the moon the gravity of the earth will continue to slow us until we reach a speed of 3.23 km/s. At this point we will be equally affected by the gravity of the earth and the moon. We will then begin to accelerate toward the moon's gravity. We need to invert the ship enroute and slow her to her lunar orbital velocity of 1.565 km/s to maintain an orbital altitude of approximatly 98 km. This burn time will be something over 30 minutes. That is as close as I am coming to doing this math. This will be the course taken by the Prophesy, unless we get a better input from the crew.

 

Bill

[ronthepon]

Sorry if this is kinda late, but

 

WOOAAAOOOOAAAHHAAAOOOOAAAOOOOAAAOOOOAAAOOHHaaaaooooo!!!

 

TFS: Shut up!! Let me WORK!!

[CraigD]

Via ground-based RADAR (real world: via the gravity simulator I used in another thread, slightly enhanced to support propulsion), I made The Prophesy passing the orbit of the Moon like a bat out of hell at an distance above Earth of 400130988 m, velocity 12789.2 m/s, at about 1441 EST. Max velocity 13049.6 m/s at DAE 91429242 m was at 0800 EST, at engine cutoff, following her 3.5 hr, .98 m.s^2 burn. Pre-burn low earth orbital velocity was 7690 m/s at DAE 400000 m.

 

I’m a little perplexed, as I’d heard she intended to orbit the Moon, but apparently she’d decided to stretch her legs a bit. Wow. :eek_big:

What should our orbital velocity around the moon be?

That depends on the altitude you’d like. The Apollo missions orbited about 100000 m above the surface, at a speed of about

[math]\sqrt{\frac{G*M}{r}} = \sqrt{\frac{6.6742e-11*7.347673e22}{1738100+100000}} = 1633.4 \text{m/s} [/math]. About 11155.8 m/s slower than that first pass. ;)

 

Though orbital mechanics as the pros do them are damn complicated (I’ve a good print textbook on the subject, but can’t claim to have mastered it :(), simulators are easy to write, and fun to use. :) With the sort of thrust The Prophesy has, it can practically be flown “by the seat of your pants”.

 

This is a really fun thread to follow! :thumbs_up

[ronthepon]

Cough! Cough!!

 

I'm taking a few days off, guys. I caught some virus from Boerseum.

 

SniFF!

[Jay-qu]

:) you to ron, things better not start getting dirty round here!

 

Craig - Pyro pulled the data from a web site, we used delta velocity of 12.5km/s to get from low earth to moon orbit

[TheFaithfulStone]

delta velocity of 12.5km/s to get from low earth to moon orbit

 

Is that right? Seems a bit high...

 

Yeah, never mind. I STILL can't figure this out.

 

TFS

[ronthepon]

12.5 Km per sec exceeds the escape velocity!

 

But who am I to question it.

[Janus]

If you want to know how the pros did it back in the day, here is a great site that shows how it was done. Craig is right. I am going to revise our burn time by quite a bit.

Hmm, your numbers are a bit off.

In our earth orbit at 400 km altitude we were traveling at 7.67 km/s. Escape velocity is 11.2 km/s. At an accelleration rate of .1g, we would need to burn the engines for roughly one hour to change our speed by 3.53 km/s at a rate of .98m/s/s.

At an altitude of 400 km, the escape velocity is only 10.85 km/sec ( (rule of thumb: escape velocity is the squareroot of 2 times larger than the circular orbital velocity for that altitude)

 

 

This one hour burn set us on our course for the moon. As we coast toward the moon the gravity of the earth will continue to slow us until we reach a speed of 3.23 km/s. At this point we will be equally affected by the gravity of the earth and the moon.

The equi-gravitational point between the Earth and Moon is at 345,660 Km from the Earth(center). If we started at escape velocity at Earth orbit, we will still be traveling at escape velocity when we reach this point. This velocity can be found by the formula, v= sqrt(2GM/d) , where d is the distance from Earth center. (345,600 km)in this case.

This gives us a velocity of 1.522 km/sec at this point. Even taking account the effect the moon's gravity has on our trajectory, we would only add about 160 m/sec to this number.

We will then begin to accelerate toward the moon's gravity. We need to invert the ship enroute and slow her to her lunar orbital velocity of 1.565 km/s to maintain an orbital altitude of approximatly 98 km.

the Moon's average orbital velocity is 1.021 km/sec.

This burn time will be something over 30 minutes. That is as close as I am coming to doing this math. This will be the course taken by the Prophesy, unless we get a better input from the crew.

 

Bill

 

If we use an escape velocity trajectory, when we reach Moon orbit, our velocity vector will point in a different direction than the Moon's . It won't be enough to just match the magnitudes, the directions will also need to be aligned. This is a slightly more complicated manuver.

 

However, there is a simpler way to do this:

If we apply a delta v of just 3km/sec, this will put us in an elliptical orbit with an apogee that puts us just inside the Moon's Hill sphere. We will also be paralleling the Moon's orbital path. A second burn at this point can put us in a lunar orbit with a perilune of 98km. Once we reach perilune, a third burn will decrease our orbital eccentricity until it is circular.

[TheBigDog]

Thank you, as always, for your wise council Janus. This is just in time for our next installment which I am beginning shortly. :eek_big:

 

Bill

[Janus]

Is that right? Seems a bit high...

 

Yeah, never mind. I STILL can't figure this out.

 

TFS

 

Quite a bit high. If you start at a 400km altitude orbit, it will only take a delta V of a tad over 3 km/sec, to alow you to intersect the moon's orbit. Once you intersect Moon orbit a delta v of 0.830 km/sec will allow you to match moon orbit. Thus you only need a total delta v of 3.830 km/sec to transfer from LEO to Moon orbit.

[TheBigDog]

OUT OF ORBIT

 

The Prophesy is equipped with a Nuclear Pulse Engine. This is a very complex device that works on a very simple process. Detonate a nuclear explosion just behind the ship and let the force push you forward. Do this rapidly enough and you will have a nearly constant force. The Prophesy has a push plate at the back of the ship that does two things. It catches a huge portion of the energy of each nuclear detonation to convert it to kinetic motion of the ship, and it shields the ship and passengers from the nuclear explosions. The push plate is perhaps the single most important part of the ship.

 

The nuclear fuel for the Prophesy is in the form of “pebbles”. These pebbles are stored in the main tank in a complex storage and delivery system, similar to how ammunition is stored for a large chain gun. Each pebble is very small, like a grain of sand, but has enough punch to push the ship forward. The throttle is adjusted by how quickly the pebbles are released into the firing system.

 

There are two phases to the firing system. The first actually shoots the pebble through the ship’s reactor to “heat” it. This brings it near to its temperature for critical mass. It passes through the reactor and through the center of the of the push plate. As it goes into the bell of the push plate the aperture it passed through closes and it passes into a focal point where it is hit by neutron beams from all sides. This begins the nuclear reaction inside the pebble. As it begins to explode its mass and energy expand outward pushing the plate and thrusting the ship forward. Large hydraulic shock absorbers allow the energy to transfer into the ship over a longer moment, making for smoother thrust. This is most critical during the first few explosions as the throttle is coming up.

 

It takes just five seconds for the Prophesy’s engine to reach full throttle. It works flawlessly.

 

 

It is 8:55 at night on what was a hot and dry late spring afternoon. It is June first. A father has brought his five young children to the park. It is unusual for them to be out this late. The young kids are bored and they are restless. Mom has spread out a blanket on the grass. They are listening to an AM radio. There are people talking instead of music and the kids have no interest at all. Dad has told them that they will see something that has never happened before. He has even brought sunglasses for everyone. That is just silly. You don’t wear sunglasses at night! But Dad’s are silly people, and even Mom is going to wear sunglasses, so the kids play along. Mom and Dad very excited about it, and that excites them.

 

The sky ranges from purple to black and is filled with twinkling stars. It is a strange night for the young children, the park is filled with hundreds of other families spread out and relaxing in the growing darkness. Suddenly the kids feel excitement coming from their parents. Children are called back to blankets. Grownups are excited and pointing to the lightest part of the sky. The older children recognize what they hear on the radio. It is a countdown. Mom has everyone putting on their sunglasses. All eyes are pointing toward the sky when suddenly... a star appears, and grows, and grows, until the star is a small sun, and the night had become day. The new sun is moving across the sky. Not fast, but not slow. And like a plane that is the glint at the head of a white trail in the sky, the small sun is shining at the front of what appears to be a glowing trail like colorful smoke seen in a flashlight beam.

 

On the east there were similar gatherings. Here the sky is darker. And people are squinting to catch the first glimmer of light on the western horizon. What they see is the pure night sky turn to sunrise. And a small sun rises in the west in defiance of all of nature’s laws. It rises in the west with all the colors of the evening sky turning into morning bright. And it continues into the bright of noon. And as it travels across the sky with its glowing plume of radiance behind it, it begins to grow smaller. Moving not just across, but away as well. Up and away into the eastern night, bright as daylight sky. Every soul on earth will remember this sight for the rest of their lives. It was the night that man defeated nature and made the sun cross the sky and fly to the moon.

 

In western Europe was the most amazing site of all. Two suns rose at the same time that morning. One in the east and another in the west. One the product of nature, the other the product of man. And the sun in the east never set. It rose high into the sky and simply went out. Leaving in its wake the a colorful glow of light that teased the vision, and ended at the crescent moon high in the morning sky.

 

 

On the ship it is a busy time. As the engine begins to fire automation takes over much of the Prophesy. Within five seconds the engine is at full throttle, pushing the ship at .1g. The push plate is absorbing huge amounts of raw energy and transferring it to the frame of the ship, pushing the ship forward in space. As the ship begins to accelerate the modules of the outer ring turn at their couplings to keep the g force always straight into the floor. The ship is moving forward and faster and away from the earth. Accelerating to its escape velocity on its path to the moon.

 

“I barely felt it.” I had known what to expect, but it was amazing all the same. I knew when it was going to happen, and despite the fact that I was laughing convulsively I had barely detected the shift when the engine started. Essentially, I had gotten heavier, like an elevator starting to lift. And that was about it.

 

“You should have been here for the test fire. When the shocks failed a tray of peeled tomatoes slid off a shelf and poured over Boerseun and down his side.” Pyro is turning red with laughter all over again. “I thought he was going to kill somebody.”

 

After a few seconds we compose ourselves and look back at the board. The better composed red-shirts running the board has anticipated the nest request and updated the flight plan on the screen. Because we had begun our trip early we would be wide of the moon. But we would be making our slow down burn at a different angle and drop into lunar orbit just as easily. We were two minutes into our initial 54 minute burn.

 

“How about this reposition between the first and second burn. Did Arcain101 het that project done?”

 

“You mean the de-spin?”

 

The de-spin had been a point of controversy among the crew for a long time. Much of the sensitive equipment, as well as not so sensitive things like plumbing, needed gravity. They needed gravity all the time. But when the ship is spinning it has so much inertia that you cannot make it change direction easily. The plan was initially to use thrusters, but that had a big problem. It used precious fuel that would reduce our mission length. So the next plan was to “de-spin” and then use the thrusters. But this required fuel for both de-spinning and re-spinning the ship. And had the extra issue of making everything in the ship go nuts while gravity was off. Normal life just cannot bounce in and out of G. But we had finally come up with a solution. In the construction phase the spokes that connect the chassis to the ring were actually crawl tubes used by maintenance personnel. They were sealed off after the ship was completed. In the final months we had made use of these 24 tubes. We put a computer controlled system of weights into them. These weights sit nearly fully extended at the beginning of the trip. As the ship rotates the weights can be pushed out and in to disrupt the balance of the ship, making her wobble. By doing this fast enough and in the correct timing you can use the natural spin of the ship to change her orientation. As the trip progresses and the spin loses its energy the weights will gradually be pulled inboard to keep a constant velocity in the ring, like an ice skater changing speed by extending or pulling in her arms while spinning. This last piece of engineering means no more de-spin. It means a much more comfortable and useful ship. And much better economy with our precious fuel. And it was made possible by a last minute engineering change by Arcain101, who had augmented the hydraulic systems in the tubes with some new technology that he brought onboard. This was so last minute that the whole of the crew is not aware of it. When the first burn ends we will see how well it works out.

 

Our attention was grabbed by a face in a new window on the main screen. It was Janus. “Pyro, I finished calculating the computer’s solution for the new course. Everything checks out.”

 

“Thanks Janus. Are you all set with the mission profiles for the landers?”

 

“Going to double check them before I hit the rack.”

 

“Roger that. Get some sleep Janus. It is going to be a busy couple of days. You need to be fresh when you take the con.”

 

“Don’t worry about that Pyro. I won’t fall asleep at the wheel. Goodnight.” And Janus signed off. He was one of the senior officers who had been rotating as the pilot. I would take my place in that rotation soon, but they were the real engineers of the ship. I would mostly be doing it during drift times. This first mission was decidedly not a drift time.

 

The burn went quickly. Having reached escape velocity we were free from the terminal influence of earth. As soon as the burn was done the modules rotated to the non-thrust position for drift. There was a momentary sensation like an elevator that was rising coming to a stop, and we all felt lighter again. We had reached the milestone for our reorientation.

 

The computer was given the command and the weights in the spokes came to life. Modulating out and in at the key point of rotation they threw the rotating wheel out of balance, forcing her to twist her orientation. Ever so slowly. Too slow to feel, but it could be seen on the graphics on the screen. It took a full hour, but the ship was turned 180 degrees, now facing with her engine forward and ready for the slowing burn into lunar orbit. But that was several hours away. Now was probably a good time to get some sleep. There were very busy times ahead.

 

“Pyro, great job my friend. Con, put me on the PA.”

 

“The intercom Con.” Added Pyro. I needed to learn some of the jargon on the ship still. Or did I?

 

“The PA Con. Make a note of that.” I know I heard Pyro mutter under his breath. I know he said “control freak”. I stood and put a hand on his shoulder giving him a wink as he shook his head at me.

 

“You are on, BD” said the red-shirt manning the con.

 

I nodded confirmation and began.

 

“Crew and guests of the Prophesy, this is your Captain. We are free of the earth and oriented for our lunar entry burn." I pause to let the exuberance to these words die down in the canteen, visible on the screen. "

 

We begin operations to the surface of the moon in 36 hours. I want to congratulate everyone one more time on such a superb job. The accomplishment that is the Prophesy is unsurpassed in the history of man. And with each day we are writing the story that will be told for the rest of man’s history. On earth, and wherever else in the universe he chooses to go." More cheers followed, but the energy is less. Adrenaline has been running high, but should begin to fade.

 

"But our mission is a long one, and is built a day at a time. We all have our mission schedules. And sleeping is going to be as important to as work. We don’t want mistakes from exhaustion. Please make sure you get to your quarters so you are fresh for your shifts. That is all.”

 

You didn’t need the intercom to hear the laughter form the canteen. I had hoped to calm everyone and get them to focus on the mission. Instead they began to pour fresh rounds and sing some kind of song they had made up about puking over the moon. Nobody was sleeping on this ship today, or for a couple of days. Not with our lunar operations just hours away.

 

"You going to bed BD?" asked Pyro with a raised eyebrow.

 

I was so exhausted I could have slept where I stood. I had experienced things today that had fulfilled my lifelong dreams. And it was the first hours of a dream that would complete my lifetime. Was I going to bed?

 

"Screw that!" I said shaking my head. "Con, we are heading to the canteen. We will be remote from there for the next... until we get back." There was a party happening. And it was time to get to know the crew just a little bit better.

 

Bill (t+2 hours)

[TheBigDog]

At the end of the space trials when we have begun our drift out toward mars I will post the compiled version of this thread including all the contributions that drive the central story line and the illustrations from the crew members. probably a week away from that at least. It will be probably 50 pages or so, depending on how wordy we all are between now and then. It is already 30 pages and I have not pulled in all of the early dialog yet.

 

Bill

[ronthepon]

What's going to be done when we reach the moon?

[TheBigDog]

What's going to be done when we reach the moon?

:hyper: Anxious? :naughty: I ain't telling yet! :hihi: