N-Prize Founder Paul Dear Talks Prizes For Nanosat Race 217
Rob Goldsmith writes to point out this interview with Dr. Paul Dear, founder of the N-Prize, and explains: "For those of you who haven yet heard of the N-Prize, the N-Prize is a £9,999.99 (sterling) cash prize which can be claimed by any individual, or group, who are able to prove that they have put into orbit a small satellite. The satellite must weigh between 9.99 and 19.99 grams, and must orbit the Earth at least 9 times. This project must be done within a budget of £999.99 (sterling)."
Get into orbit for a grand? (Score:4, Interesting)
What is a sterling? Pound? (Score:1, Interesting)
A rocket scientist asks... (Score:5, Interesting)
Is this some prototype for a global diamond delivery system? Serious, apprise me of the value of putting less than an ounce of something into orbit. And it's the "orbit" part that's tricky. A sufficiently large model rocket can do Alan Shepard-esque sub orbital flight. But to then pop it into orbit with a "circularizing burn" is tricky... on a budget.
I'm trying to not be a troll here, but this prize is designed to develop a $2K ICBM for very tiny payloads. If you put VX gas into something that might survive reentry, you'd have the plot for an Austin Powers movie. I'd call it "MoonShagger: It's a gas gas gas."
Re:Get into orbit for a grand? (Score:3, Interesting)
Brilliant meme! (Score:5, Interesting)
Request For Comets (Score:2, Interesting)
Re:A rocket scientist asks... (Score:4, Interesting)
You need to get an antenna and transmitter powerful enough to be trackedfrom earth an weighting 20 grams. Or put up some sort of light radar reflecting sail (only has to orbit 9 times on LEO and burn up, doesn't say it has to do anything useful).
I wonder if the tracking side is included in the budget or if you can borrow some really big antenna to try to detect the junk you put up.
Re:Request For Comets (Score:3, Interesting)
Re:"D" Engines (Score:2, Interesting)
I remember seeing an analysis of this idea quite a few years back. In short, in order to add enough thrust using "D" engines to make it to orbit, you add so much extra weight that you'll never make it to orbit ... adding still more engines just compounds the problem.
Of course, this analysis was done assuming launch from ground, not launching from ... say ... a balloon launch platform at 20000m
Re:A rocket scientist asks... (Score:3, Interesting)
Or, maybe it is a government-involved program to find all those who are capable of launching objects to LEO, to add them to a watch-list so that if the terictz come sweet-talking them, the government will have a one-up. Or, wait, maybe it's the terictz who are looking for those with the know-how to get to LEO. Or, wait, maybe it's just CowboyNeal and... and..
Re:Get into orbit for a grand? (Score:3, Interesting)
I can't find it now, but I remember stumbling across an amateur rocketry web site where the author (a licensed ham) had ground down a PIC chip (I think it was a 16C84 or 16F84) from 16 pins to the middle 8 pins, added a small clock crystal, watch battery, and a little antenna wire. The PIC repeatedly transmitted the author's callsign in CW on some HF frequency, performing the modulation in software.
9 orbits is only 7 hours. I'm pretty sure you could put that much battery in it and still be under 20 grams.
Re:A rocket scientist asks... (Score:2, Interesting)
Re:A rocket scientist asks... (Score:3, Interesting)
Re:A rocket scientist asks... (Score:4, Interesting)
delta-V = 9.8 * Isp * ln (Mass1 / Mass2)
Where delta-v is the change in velocity required (8-10 km/s for orbit), mass1 is the lift off mass, mass2 is the on orbit mass, and Isp is the specific impulse which is a parameter of engine design primarily effected by propellant choice. Isp varies between 100 and 450 seconds - the SSME is 450 seconds, an estes model rocket gets 100 or so seconds.
So the above example is a back of the envelope calculation for a conceptual rocket - mass1 is 10 kg, mass2 is 0.5 kg, Isp is 280 s. This gives you a delta v of 8.2 km/s, which is enough to reasonably be expected make orbit (assuming that orbit is possible at all, of course - I mean the basic engineering premise is a bit of a stretch, but the physics works).
Re:Delta-V = *** FAIL *** (Score:3, Interesting)
I AM a degreed Aerospace Engineer who worked in El Segundo for a company that is now known as Boeing. Savvy? I worked with real rocket engines (Marquardt 5lbf and 100lbf [aiaa.org] I knew Gil and Phil...), loaded bi-propellant into very thin titanium tanks, and worked with those who worked with the solid motors, including the PAMs. (yeah, them). Now, I grant you i'm rusty, so that I had to look several times to make sure your Delta-V equation was correct. So, here's some more that you neglected.
Re:Delta-V = *** FAIL *** (Score:3, Interesting)
OK, well getting into a credentials pissing contest with a pseudo-anonymous person is just silly - especially since, if what you say is true, our credentials are orthogonal. (My title has three letters in it, and my budget is much larger than yours I'd bet)
But, as I said, I'm pseudo-anonymous, your pseudo-anonymous - so let's let the math speak for us:
Wave drag + stagnation temperature - you seem to be assuming high velocities in the atmosphere which, as you point out, is probably a sub-optimal design. Fortunately I assumed no such thing - I was doing a back-of-the-envelope calc, and just assumed that getting 10 kg clear of the appreciable atmosphere was not going to be a challenge, as balloons do that every day, etc. BTW, I did include "wave drag" and every kind of drag in my "couple of hundred m/s. Obviously, you could challenge that and I would not try to back it up - I'm not interested in this contest, except possibly as an advertising vehicle, so I am hand waving a lot of issues aside. (As I am sure you know, stagnation temperature means nothing - it is the temperature of the air a few feet in front of you. You want to calculate the heat flux transmitted to you by it, but fortunately you do not ever have to survive that temperature. Otherwise, no one would ever pass mach 5 or so - indeed, for a long time it was thought to be impossible)
Combustion pressure - Look, I hate to be rude, but this paragraph really doesn't sound like it was written by an aerospace guy. The engine pressure needs to be at least 3 times the external pressure or so (minimum design point). Since the burn will start way out of the atmosphere, that pressure will actually be limited by your combustion process rather than external pressures. Your pressure vessel calculations are, well, wrong. Tank mass scales directly with pressure and volume - and tanks do not care much about shape (as long as you have directional strength capabilities). That said, enclosing your entire propellant supply at full operating pressure is unlikely to be optimal - there are many ways to raise the propellant up to pressure as it is used, as I'm sure you realize. The critical point here is that engines with a T/W ratio of 100 are pretty easy using dense propellants. This really isn't the issue you seem to think it is.
Guidance, Circularization - OK, a lot of this just gets chalked up to the agreed premise that only thrusting in the atmosphere is dumb. But since I was talking about a rocket, rather than Bull's cannon, that is beside the point. Guidance is very hard - but not for the reasons you claim. Vectoring thrust is easy, proven and addresses all of your claims. What you missed is that while engines, tanks, and thrust vector control systems scale with vehicle size - guidance computers do not. This is a real problem for a 500 gram rocket - and is one of those things that you would have to design around.
Final stage - OK, if there was a point here, I missed it. I proposed an SSTO, which you say is dumb (words I believe you will eat inside 10 years). You then said that adding staging hardware eats mass (sort of - I submit that SSTO is harder and therefor heavier, but whatever). While true, it does not really apply.
You also mentioned performing a shuttle boost trajectory - that would not be very clever, since the shuttle only does that because they need to hit a particular orbit and have to launch from Florida. This project has no such requirements - obviously you would go to the equator and launch due east, for maximum boost.
On your engineering claims, I know how I would attempt it if I wanted to (somehow, dreams of $20K just don't excite me anymore) but I don't want to discuss that in an open forum. (You do know about ITAR, right?)
Let me just say that in regards to engineering (and science, for that matter), never believe someone who says it cannot be done. You cannot prove something impossible, and existenc
Re:What is a sterling? Pound? (Score:2, Interesting)
Offtopic, but couldn't everyone here use GBP, USD, EUR etc. instead of the various currency symbols which get trashed on slashdot?