kme
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Re: Orbiter.

Fri Nov 18, 2011 8:11 pm


The Everest post is no such a bad idea. Sending a orbiter that height would be a real help. But move your thought process away from Everest and move it to Hawaii, were the worlds real highest mountain is (Thank you Qi)

I don't know if anyone knows the place I am talking about, It is the place in Hawaii That has lots of international space telescopes on it. It is so high that you can suffer high altitude sickness.

There is a major plus to this location as well. It is easier to get to, since there are scientists up there all the time.The lousy 8,8 km doesn't make any difference (and a submerged mountain is useless). It's all about speed if you want to reach orbit. There is a reason why you fly horizontal once you reach ~150 km and a reason why everyone prefers a spaceport at equator - but only few has the chance. ESA is very lucky with Kourou.

wrhii
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Re: Orbiter.

Fri Nov 18, 2011 8:23 pm

Might want to just consider going underwater instead. Lot of places to visit underwater, and really interesting things you could learn that "going to space" might not get you.

Plus, getting to sea level is generally pretty easy, the hard part is going deep. Now, going into orbit is both hard, and surviving to tell the tale is nearly practically impossible. Going deep, you can test in much smaller increments to avoid massive loss of funds from the venture.. Of course, as with going into space power would be a problem when going deep, so your mileage may vary.

Bacan
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Re: Orbiter.

Fri Nov 18, 2011 8:47 pm

Quote from MDC on November 18, 2011, 20:08
Quote from Bacan on November 18, 2011, 19:43
It is also Sacred to the Native Hawaiians.

Didn't know that :? .
One question though, if it is a sacred place to them why have they let people build on it?

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Burngate
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Re: Orbiter.

Sat Nov 19, 2011 11:48 am

Sri Lanka (Arthur C Clarke). Or where did Charles Sheffield use for his base?

WizardOfOZ
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Re: Orbiter.

Sat Nov 19, 2011 5:56 pm

You needn't concern yourself with using civilian electronics: Pi, cell phones, doesn't matter. All the usual terrestrial stuff is way too sensitive to radiation to be of any use, as was already mentioned.

While the Apollo capsule computer didn't have much in the way of processing power, the semiconductor structures in it were many orders of magnitude larger than any modern consumer MCU. This made it especially well suited for its purpose, working reliably despite a high background radiation.

Some exceptionally strange materials are in use in space rated ICs to make them work, including oversized Silicon structures on a base of diamond film. That kind of thing. :)

No rad hardened navigation computer: Don't bother. It is likely to crash, rocket as well as computer.

I would start by writing a physical simulation of the planned flight in a computer to get some idea of the scales and basic problems involved, then take it from there. You will need a solution for the orbital mechanics eventually, so may as well start with one of the easy bits.

Edit: The late Arthur C. Clarke took liberty with the location of Sri Lanka in "Fountains of Paradise", moving the island about 6 degrees south to place it on the equator. In the real world French Guyana is the better location for launching rockets (though not by much).

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Burngate
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Re: Orbiter.

Sun Nov 20, 2011 11:32 am

Quote from WizardOfOZ on November 19, 2011, 17:56
Edit: The late Arthur C. Clarke took liberty with the location of Sri Lanka in "Fountains of Paradise", moving the island about 6 degrees south to place it on the equator. In the real world French Guyana is the better location for launching rockets (though not by much).
And Charles Sheffield's "The Web Between the Worlds" (also 1979) is back on my to be re-read pile.
My point, actually, was that Everest / Hawaii doesn't gain you much. If you have a problem (which you do) with the amount of fuel needed to rise above the atmosphere and gain speed to enter orbit (two separate problems, the second being larger), and if you're willing to consider next-generation technology, then a beanstalk is a better solution. Wikipedia is, as ever, a good starting point.
But, that said, having got into orbit, that is only the start.
There have been amateur satelites in orbit, notably (I believe) Surrey University.
Low earth orbit is less harsh than higher up.
My take on this thread is that, if you can get to orbit, should you take a Pi? To which the answer has to be It depends on what you want to do. Also, yes the Pi quite possibly has the power to control the rocket, and would be easier to interface to it than an iPhone. You would, however, have to convince the builders of the rocket that your Pi was a better solution than the one they've already adopted, and since they're now spending their time arguing over details such as the cooling of the exhaust nozzles they'll probably not thank you for your input.

WizardOfOZ
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Re: Orbiter.

Sun Nov 20, 2011 12:07 pm

Quote from Burngate on November 20, 2011, 11:32
There have been amateur satelites in orbit, notably (I believe) Surrey University.
There have been about 3 dozen by now, notably the AMSAT family of amateur radio satellites. The satellite from Surrey University was OSCAR-22 (Orbiting Satellite Carrying Amateur Radio). These are all being built to commercial satellite technical standards, or they wouldn't be allowed to fly on commercial launch vehicles as 'carry on' luggage (meaning they fly in addition to the paying customer's payload).

Quote from Burngate on November 20, 2011, 11:32
Low earth orbit is less harsh than higher up.
Less harsh doesn't mean benign, check for instance the info on WikiPedia on the Southern Atlantic Anomaly. All flight computers must be radiation hardened. Period. Commercial electronics not intended for mission- or life critical systems are allowed on manned flights, but they cannot do anything important.

You may remember that a Russian supply ship collided with ISS a few years back? The reason for the crash was that the Russian flight controllers had deliberately switched the docking computer off(!). They wanted to 'check' if they could dock manually without using the Ukrainian built docking computer. This would allow the Russians to save a lot of cash for each supply vessel, as the Russian Federation could then save the payment to Ukraine for this particular computer. Should give you some idea of the price tag.

Quote from Burngate on November 20, 2011, 11:32You would, however, have to convince the builders of the rocket that your Pi was a better solution than the one they've already adopted,...
No need to speculate. Your rocket won't be authorized to fly without rad hardened flight computers. In fact the relevant people will laugh at you for suggesting using a Pi for the job. Then they will call for security to escort you off their premises.

sh4d0w0lf
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Re: Orbiter.

Sun Nov 20, 2011 1:00 pm

Quote from Gert van Loo on November 18, 2011, 08:46
No body tried to launch a rocket from a weather balloon?
should get you twice as high.



That's what i was thinking

WizardOfOZ
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Re: Orbiter.

Sun Nov 20, 2011 1:27 pm

Quote from sh4d0w0lf on November 20, 2011, 13:00
That's what i was thinking
Write a computer simulation for the crude case of a flight to orbit partitioned in two parts:

First part is a trajectory starting at the Earth's radius, going straight up to an altitude of 200km. Ignore air resistance for starters.
Second half is a flight accelerating horizontally in zero gravity (weightlessness) from rest to 7km/s (25'200 km/h). Your target weight in orbit is one kg.

The second half should be done first to determine the weight of the rocket at 200km altitude, including remaining fuel. Both of these steps can be done by a straightforward numerical integration of Newton's laws, using nothing but simple programming techniques and high school physics. You are free to use any fuel you like, including liquid Hydrogen and Oxygen. Multiple stages, to shed as much weight as possible during the flight, are allowed as well, of course.

Find the total take-off weight and fuel-to-rocket weight ratio to get one kg into orbit by simply adding up the requirements of these two steps.

I believe you will find that the rocket will be a tad too heavy for a weather balloon, and that the 30 km difference in altitude won't make much of a difference.

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Re: Orbiter.

Sun Nov 20, 2011 3:03 pm

Quote from WizardOfOZ on November 20, 2011, 13:27
Quote from sh4d0w0lf on November 20, 2011, 13:00
That's what i was thinking
Write a computer simulation for the crude case of a flight to orbit partitioned in two parts:

First part is a trajectory starting at the Earth's radius, going straight up to an altitude of 200km. Ignore air resistance for starters.
Second half is a flight accelerating horizontally in zero gravity (weightlessness) from rest to 7km/s (25'200 km/h). Your target weight in orbit is one kg.

The second half should be done first to determine the weight of the rocket at 200km altitude, including remaining fuel. Both of these steps can be done by a straightforward numerical integration of Newton's laws, using nothing but simple programming techniques and high school physics. You are free to use any fuel you like, including liquid Hydrogen and Oxygen. Multiple stages, to shed as much weight as possible during the flight, are allowed as well, of course.

Find the total take-off weight and fuel-to-rocket weight ratio to get one kg into orbit by simply adding up the requirements of these two steps.

I believe you will find that the rocket will be a tad too heavy for a weather balloon, and that the 30 km difference in altitude won't make much of a difference.

Good point, but I wasn't thinking of attempting this.

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zebo-the-fat
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Re: Orbiter.

Sun Nov 20, 2011 3:30 pm

"First part is a trajectory starting at the Earth's radius, going straight up to an altitude of 200km."

"Second half is a flight accelerating horizontally in zero gravity (weightlessness) from rest to 7km/s (25'200 km/h)."

If you go straight up to 200Km, you will not be in zero G, you will have almost full earth gravity, (slightly less as you will be further from the centre of the earth), you only get zero G when you are in orbit. (or did I misunderstand something?)
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WizardOfOZ
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Re: Orbiter.

Sun Nov 20, 2011 3:52 pm

Quote from zebo-the-fat on November 20, 2011, 15:30
If you go straight up to 200Km, you will not be in zero G, you will have almost full earth gravity, (slightly less as you will be further from the centre of the earth), you only get zero G when you are in orbit. (or did I misunderstand something?)
No, you didn't miss something. I was describing a simplified model of the flight, which would be easier to calculate. In reality you would do the two trajectories simultaneously, mostly thrusting horizontally once you get above the bulk of the atmosphere, yet still using the engines to balance Earth's gravity and slowly lift the rocket into orbit.

My simplification works because the total energy required has two major components with little connection (the forces involved do in fact act at perpendicular axes for a circular orbit): The energy required to lift the rocket up through the Earth's gravitational field, and the energy required to accelerate it horizontally (in zero Gee) from zero speed and up to orbital velocity.

The combined energy required for the two phases will be fairly close to the real thing, even if the individual trajectories are totally unrealistic. For kicks consider that the best vertical ascent would leave the rocket at zero velocity at a height of 200km. So we need to coast with engines off for some time during the first phase to minimize fuel consumption, then restart the engines when trying to gain orbital velocity. :D

PS: Check whether the 7 km/s target velocity includes the Earth's rotational speed at the equator.

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Re: Orbiter.

Sun Nov 20, 2011 3:56 pm

Ok, makes more sense looking at it that way :)
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Re: Orbiter.

Sun Nov 20, 2011 4:15 pm

WizardOfOZ is right as usual
Just my point was: down here we have an atmosphere and a magnetic field protecting us. In low earth orbit we don't have the atmosphere but we do have the magnetic field. Further up we have neither. Ball-park figures: the atmosphere is similar to a lead shield 1m thick.

WizardOfOZ
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Re: Orbiter.

Sun Nov 20, 2011 5:11 pm

Quote from Burngate on November 20, 2011, 16:15
WizardOfOZ is right as usual
Just my point was: down here we have an atmosphere and a magnetic field protecting us. In low earth orbit we don't have the atmosphere but we do have the magnetic field. (Snippety).
Actually, the linked article about the SAA provides a link documenting we don't even have the benefit of the magnetic field in orbit:

"Designers also found out that laptops would crash when the shuttle passes through the "South Atlantic Anomaly," which is an area where the magnetic field draws in to Earth, again offering less radiation filtering for spacecraft flying through it."

Civilian computers are quite unreliable, even in low Earth orbit.

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Re: Orbiter.

Sun Nov 20, 2011 5:48 pm

Quote from WizardOfOZ on November 20, 2011, 17:11
Quote from Burngate on November 20, 2011, 16:15
WizardOfOZ is right as usual
Just my point was: down here we have an atmosphere and a magnetic field protecting us. In low earth orbit we don't have the atmosphere but we do have the magnetic field. (Snippety).
Actually, the linked article about the SAA provides a link documenting we don't even have the benefit of the magnetic field in orbit:

"Designers also found out that laptops would crash when the shuttle passes through the "South Atlantic Anomaly," which is an area where the magnetic field draws in to Earth, again offering less radiation filtering for spacecraft flying through it."

Civilian computers are quite unreliable, even in low Earth orbit.

I think they are quite unreliable at ground level too. Especially if they run Windows!
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Andre_P
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Re: Orbiter.

Mon Nov 21, 2011 12:46 pm

Hi All,
A couple of thoughts.

First for orbital mechanics : http://www.amazon.com/Fundamen.....0486600610

Secondly : I wonder how big a Magnet you would need to provide a similar level of protection and could you put it in a large water bottle as well.

Dare I say it I believe Xilinx and Altera do indeed have rad hardened FPGAs, it might be better to get a softcore in there and use that. No idea how expensive they are, not cheap I suspect but if you are serious about this then you could approach them, might give them some kudos if you succeed.

iamnull
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Re: Orbiter.

Thu Nov 24, 2011 8:55 am

Edit: Whoa! Didn't notice this had gone to five pages when I replied! This reply was in the context of only reading to the last reply on the first page.

Quote from jamesh on November 17, 2011, 14:31
In case you don't know, only one non-governmental organisation has EVER put something in orbit. SpaceX. Cost $100Million.

There is a competition in full swing at the moment called the N-Prize for orbital attempts. but no-one has won that yet. Or even got close.

John Carmack of Doom/Quake/Rage fame runs Armadillo aerospace and has a lot of rocket experience. His last effort to just get to 100kft crashed and burned. (STIG)

Copenhagan Sub orbitals are trying to get to orbit - they had a low altitude test earlier this year which sort of failed. At least it left the pad.

All the above use customised electronics. I think a mobile may not be robust enough for what you are planning. A raspi might work, and would be easier than modifying a phone. As someone else said, the electronics are by far the easy easy easy easy bit. If you think they are hard, then you might have trouble grasping how difficult getting stuff up there is. It's not that rocket science is difficuly, it's that rocket engineering is VERY VERY VERY difficult.



o.O Never said I thought the electronics were hard. Finding a way of keeping them from melting actually seems more daunting than the wiring and coding. I'm not quite sure how to regulate the temperature of the circuits and batteries. They'll be facing extreme cold and a buildup of heat.

I have one single advantage over pretty much every private company trying to get to space: I'm not invested in recovering the craft, I have no intentions of it being used to collect any valuable data, and I'm not designing it with the hopes of turning it into a manned launch vehicle. That should cut the costs significantly. Optimistically, it could reduce the cost under $100k. Less optimistically, it'll represent the cost of a very nice house. No, I have no idea where funding would come from. At this point trying for even a ballpark cost estimate would be purely pulling a number out of my bum.

As I said, the liquid fuel system is the biggest problem. It's going to probably have to be custom built, most likely out of aluminum or titanium, and it'll have to be done right. I cant seem to find a lot of verifiable information, just vague descriptions of various parts. Unless I can find hard information on things like how differently shaped injection ports affect the injection of O2/H2 into the combustion chamber, I'm pretty much dead in the water. The information is out there, I just don't know where to go to get it.

To be honest, I thought nobody had actually successfully orbited a private craft. Reading about it, it doesn't surprise me that I missed that since I was really busy when they launched that vehicle.

iamnull
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Re: Orbiter.

Thu Nov 24, 2011 9:37 am

As WizardOfOZ noted, weather balloons probably wont work. It was actually my first thought since I figured it'd help through the most fuel intensive part of orbital entry. I evaluated it with a relatively low weight of 200lbs. I didn't delve into it too deeply, but here's my basic train of though:

You're only covering ~15% of the total journey with those balloons. Yes, it's the most difficult part of it with the highest fuel consumption, but you're adding a LOT of complexity for a little gain. The biggest problem is that you'd have to disengage the balloons with either a clamping system or something like an incendiary system. More parts means a higher probability of failure. It's an interesting novel solution, but I don't think it'd be worth the added cost and difficulty. You'd have to cover almost all the same problems with the added difficulty of an unpredictable launch location. It could drift miles off course. Not to mention, you'd have to ignite the engine, disengage the balloons and then just cross your fingers that the stabilizing thing (I honestly cant remember what it's called, but it's like a gryo, except heavier) isn't overwhelmed by a gust of wind against the craft which has very little momentum with which to resist the wind. There's also the difficulty of predicting how quickly you'll be travelling from the balloons alone and what effect disengaging will have. Oh, and you'd have to release at a sub-optimal height since you don't want the balloons popping. It'd probably release at something like 19km as opposed to the potential maximum of ~25km.

My original design was a basic delta wing strapped to a multi-stage booster. That's just too much effort for too little gain. I've moved on to a more capsule like craft, mainly because it'll make just about everything easier, and cheaper.

For shielding, could you potentially simply use thin lead on the inside of ceramic? Heck, could you even just use a layer of ceramic, gold foil and then lead foil? The less lead used the better, so any solutions to that would be great. Would that provide enough protection to avoid causing problems?

I very much appreciate the discussion and input!

Thank you Andre_P for that link. I'm going to buy that since I do have an Amazon coupon to use.

Edit to avoid multi-post:

I'm having trouble getting any kind of hard figures since I lack one very crucial thing: the amount of thrust being produced by the individual stages. I don't have the engineering background to even roughly predict the amount of thrust that the liquid engine would produce given a set of dimensions. I'm struggling to work out the formula, but it's rather daunting. I'm not exactly sure how, formulaicly, the expansion of gasses in x sized chamber translates into thrust through y sized nozzle. The good news is the amount of energy produced for both solid and liquid fuel combustion mixes is fairly well documented. I need a couple good books on things like thermodynamics and trigonometry.

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Re: Orbiter.

Thu Nov 24, 2011 11:41 am

Re rocketry-type stuff. A while ago I and my wife and daughter visited an aircraft museum - was it Hendon? Duxford? not sure now - they had a V2 rocket. What impressed me was the complexity of the thing - and this is 70 years ago, only suborbital. Things they had to consider where how to cool the chamber where the fuel met the oxidiser, to stop it melting (the fuel was pumped round it before it went into the chamber) and indeed how to pump the fuel (those pumps themselves where works of art).
Also of interest is a photo my daughter took at Salford University.

Re shielding. To a first approximation, mass is what you need. OK, some things are better than others - boron works best for neutrons. But our atmosphere has 15 pounds of air above every square inch at the surface. That's the same as 30 feet of water, or 30 inches of mercury, or 3 feet of lead. Any less, and you get less shielding. To a certain extent a thin layer of lead would in fact be worse than nothing - what's out there is mainly very fast protons, and with no shielding at all, they'll go straight through silicon, damaging the crystal structure and discharging any capacitors on the way. Put some lead in the way, they'll hit some neuclei on the way, creating showers of secondary particles, each of which will do damage, so the shielding in fact multiplies the problem!
I'm assuming you're not aiming to go through the Van-Allen belts. They're very bad news. Discovered in 1958, if I recall, when a geiger counter was sent up and through them. The out-put from the counter rose steadily then suddenly dropped to zero, which surprised the scientists. In fact the radiation hadn't dropped, it had saturated the geiger tube. See Wikipedia (of course) for more.
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iamnull
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Re: Orbiter.

Thu Nov 24, 2011 12:17 pm

Burngate, thanks! I'm actually hoping the liquid thruster will use the fuel to cool the combustion chamber. I'd like to get my hands on a fairly simple engine that uses this type of cooling to see how and why it's done. Or even just renderings would be massively helpful.

As for shielding, I don't think three feet of lead is an option, lol. Found this googling around:
http://www.islandone.org/Settl.....hield.html

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Re: Orbiter.

Thu Nov 24, 2011 12:22 pm

Quote from iamnull on November 24, 2011, 08:55
Edit: Whoa! Didn't notice this had gone to five pages when I replied! This reply was in the context of only reading to the last reply on the first page.

Quote from jamesh on November 17, 2011, 14:31
In case you don't know, only one non-governmental organisation has EVER put something in orbit. SpaceX. Cost $100Million.

There is a competition in full swing at the moment called the N-Prize for orbital attempts. but no-one has won that yet. Or even got close.

John Carmack of Doom/Quake/Rage fame runs Armadillo aerospace and has a lot of rocket experience. His last effort to just get to 100kft crashed and burned. (STIG)

Copenhagan Sub orbitals are trying to get to orbit - they had a low altitude test earlier this year which sort of failed. At least it left the pad.

All the above use customised electronics. I think a mobile may not be robust enough for what you are planning. A raspi might work, and would be easier than modifying a phone. As someone else said, the electronics are by far the easy easy easy easy bit. If you think they are hard, then you might have trouble grasping how difficult getting stuff up there is. It's not that rocket science is difficuly, it's that rocket engineering is VERY VERY VERY difficult.



o.O Never said I thought the electronics were hard. Finding a way of keeping them from melting actually seems more daunting than the wiring and coding. I'm not quite sure how to regulate the temperature of the circuits and batteries. They'll be facing extreme cold and a buildup of heat.

I have one single advantage over pretty much every private company trying to get to space: I'm not invested in recovering the craft, I have no intentions of it being used to collect any valuable data, and I'm not designing it with the hopes of turning it into a manned launch vehicle. That should cut the costs significantly. Optimistically, it could reduce the cost under $100k. Less optimistically, it'll represent the cost of a very nice house. No, I have no idea where funding would come from. At this point trying for even a ballpark cost estimate would be purely pulling a number out of my bum.

As I said, the liquid fuel system is the biggest problem. It's going to probably have to be custom built, most likely out of aluminum or titanium, and it'll have to be done right. I cant seem to find a lot of verifiable information, just vague descriptions of various parts. Unless I can find hard information on things like how differently shaped injection ports affect the injection of O2/H2 into the combustion chamber, I'm pretty much dead in the water. The information is out there, I just don't know where to go to get it.

To be honest, I thought nobody had actually successfully orbited a private craft. Reading about it, it doesn't surprise me that I missed that since I was really busy when they launched that vehicle.

I'm afraid you are still woefully underestimating the complexity of a rocket. Ignore the electronics, that the easy bit. The fact that you have never heard of SpaceX (I assume that's who you refer to), means that you really haven't looked in to this enough.

There are lots of people (not just companies) who have had the same aims as yourself - not bothered with manned (Armadillo), not bothered with recovery (Copenhagan, SpaceX [yet]), not worried about data (most of them).

Have you ever designed or run a rocket engine? Lots of people out there have (see arocket list for example, Tripoli rocket association etc), and NO-ONE except SpaceX (after > $100mill) has put something in orbit.

$100k won't get you very far at all. Probably not even the custom parts for a nozzle + tanks + plumbing. You cannot buy rocket engines capable of orbital ISP, you have to make them yourself.

I think Armadillo's STIG rocket cost about $50k. And failed on its first launch due to aerodynamic issues - see their website. This is from a company that spent the last 10 years perfecting their rocket engine.

There is LOTS of information out there, read it.
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iamnull
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Re: Orbiter.

Thu Nov 24, 2011 1:35 pm

I've heard of SpaceX before, jamesh, sorry if I didn't make that clear. I missed the news about that launch because I was busy in school. Early December is around finals. I've also had many model rockets, mostly the little cardboard estes rockets. Please, don't think I'm uninformed or naive simply because I'm not entirely forthcoming with every detail.

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Re: Orbiter.

Thu Nov 24, 2011 2:01 pm

OK, then a couple of pointers. Don't go for H2/O2. Way too expensive and dangerous. Kerosene/LOX is the best option. Or perhaps methane/LOX, Armadillo have been testing that combination for NASA. H2O2 isn't good enough.

The Arocket list has recently had some posts on good rocket book to read. Join the list - a lot of professionals and high end amateurs hang out there.

Don't forget that for any flights over a certain altitude, and certainly orbital, you need governmental permission (if you are American, you need permission from the USA government WHEREVER you launch from in the world), and you also need a very comprehensive dispersion analysis in case things go wrong (An orbital rocket could fall anywhere). The required software to do that sort of thing costs in the large thousands.

Get saving. This will cost a lot. The insurance costs will be pretty eye watering for start.
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Re: Orbiter.

Thu Nov 24, 2011 5:49 pm

Thank you jamesh, I'll look for those books. I've been wondering about permits and all that. Didn't even think about insurance. I figured I'd wait until I was actually on the road to having parts fabricated and such before starting to process of getting permission from the gov't. I just assumed it'd be a 6mo to 2 year process to get a launch date, no matter if the craft was ready to go or not.

Since the information is readily available on wikipedia, I'm gonna dive into the mathy parts of figuring out the liquid booster using Kerosene/LOX. I've set up a subsite on a site I own to help me keep track of my work on this and collaborate. If anyone wants the link, pm me. Figure it's better to take the non-RPi discussion off the RPi board.

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