I always thought that to get to a suitable HEO you need to start at a suitable GTO and not LEO.

I guess they forgot to mention that at the conference? So it doesn't matter what the propulsion is unless you start at the right orbit it is not of much use. Getting to GTO is the money issue. No free rides to GTO.

In addition, doesn't the process getting from GTO to HEO require some form of rapid acceleration? If yes, ion engines and solar sails are out.

Thoughts?

Stefan, VE4NSA

On Sun, Apr 28, 2013 at 2:05 PM, George and Cheryl Abbott [email protected]wrote:

Great Job!73 to all. George, W1GMA.QTH about 20 south west of the Roger Williams Park Zoo.

-----Original Message----- From: Lizeth Norman Sent: Sunday, April 28, 2013 2:35 PM To: Nick Pugh Cc: [email protected] Subject: [amsat-bb] Re: Path to HEO

Sign me up. Sounds like the next big thing. 73 de Norm n3ykf

On Sun, Apr 28, 2013 at 2:14 PM, Nick Pugh [email protected] wrote:

I have just returned from a satellite conference and I think new

...

technology will now give us a path to HEO. Challenging of course but for the clever doable. Please take a look at a ~ 2 minute video that tells how

http://www.youtube.com/watch?**v=TpGnxlZC8Hshttp://www.youtube.com/watch?v=TpGnxlZC8Hs

Thanks

nick ARS K5QXJ EM30xa 30.1N 92.1W

Office 337 593 8700

Cell 337 258 2527

Helping UL become a world Class Engineering and Educational School

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--- On Sun, 28/4/13, Stefan Wagener [email protected] wrote:

I always thought that to get to a suitable HEO you need to start at a suitable GTO and not LEO.

There's no reason why you couldn't go from a 310 km LEO orbit, it just takes time.

Romit-1 is a 2U CubeSat developed by Euroluna volunteers. It has an ion engine and they reckon it'll take a year to go from a 310 km orbit to 700 km. With Ion motors you can get CubeSats to decent orbits even if the initial deployment is into one of the cheapest 310 km orbits but you may have to wait a few years.

The problem at the moment is the shortage of low-cost LEO launches. Currently a 2U launch would cost you about $150,000+ Hopefully launch opportunities will increase and prices fall in the coming years. Certainly Federal Government funded CubeSat launch programs such as ELaNa, would be one option in the 2015-2018 time frame for those in the US.

I think Euroluna have been waiting 2 years now for a launch, there are a number of other groups also trying to fly CubeSat's with Ion Motors.

Some info on Romit-1 is at http://amsat-uk.org/2012/03/01/euroluna-oz9luna-cubesat-launch-update/

73 Trevor M5AKA

Thanks,

maybe I didn't make myself clear:

LEO (low earth orbit) from 400 to 2000km or something like that HEO (high earth orbit) >20000km

Going from 310 to 700km in a year is not doing us anything. We need a highly elliptical orbit (Apogee ~60000km, Perigee 900km) similar to AO-40 to allow for cross continental communication.

Stefan VE4NSA

On January 23 I was on UL mode with a DL and an Italian station i was just testing my new L Band amp and it was my 802 QSO on AO-40 my last one snif snif. The rest is old story who can be shared only with those guys who enjoy one of the best AMSAT satellite.

For those who just start to flirt with satellite here is how the story end

On 25 January 2004, telemetry from the main battery was observed to go to an extremely low voltage by Stacey Mills (amateur radio call sign W4SM), a member of the Command Team. This caused the onboard Internal Housekeeping Unit (IHU) computer to cut power to the transponder payloads. Just prior to the loss of control of the satellite, the auxiliary battery came online in parallel with the main battery. When the main battery failed, it effectively short-circuited the auxiliary battery, killing the spacecraft. Many attempts were made to disconnect the main battery, but insufficient voltage was available to drive the relays. One day an open-circuit failure may occur in the main battery, in which case the spacecraft may come to life again. Though the command team believe that the main battery failure was probably a consequence of damage done during the event, and it is likely that similar damage was done to the auxiliary battery, making an eventual recovery of AO-40 unlikely.

What the story does not tell it is possible that a manual command was the culprit here but all the folks who work on the AO-40 project are also human and perfectible as you and me.

It is a refreshing breeze to start to hear HEO again so sorry for those who pass by to the eternal DX cluster.

"-"

Luc Leblanc VE2DWE Quebec provincial Hamfest HTTP://www.hamfest.qc.ca DSTAR urcall VE2DWE WAC BASIC CW PHONE SATELLITE

Thanks Bob,

That's why it is important to read the complete conversation.

This is NOT about Cubesats, staying in orbit, etc. It is about getting into an HEO beyond 20000km.

On Mon, Apr 29, 2013 at 1:34 PM, Robert Bruninga [email protected] wrote:

...

Going from 310 to 700km in a year is not doing us anything.

Im not following this closely, but that statement misses the most important reason for doing this...

*to*stay*in*orbit!

The lifetime of a cubesat at 310km is only a few weeks at most. The life time at 700km is tens of years.

The minimum requirement then for an ION thruster, then, is to be able to at least be slightly greater than the loss on every orbit. Then it is worth its weight in gold!

Bob, Wb4APR

Thanks,

I like simple math. A 3U Cubesat can have deployable solar cells which will give you between 45 and 70 watts of power. That should drive an ion engine. Will need an active attitude control system and should start at the right orbit. Getting +-3kg to GTO is a $100.000? Don't know what the satellite would cost but we are now in a $ range that could be funded.

Thoughts?

Stefan

On Mon, Apr 29, 2013 at 2:50 PM, Patrick Strasser [email protected]wrote:

schrieb Stefan Wagener on 2013-04-29 01:29:

...

LEO (low earth orbit) from 400 to 2000km or something like that HEO (high earth orbit) >20000km

Going from 310 to 700km in a year is not doing us anything. We need a highly elliptical orbit (Apogee ~60000km, Perigee 900km) similar to AO-40 to allow for cross continental communication.

Let's check with some maths (*):

Energy at 300 km:

Total Energy = kinetic energy + potential energy E_kin + E_pot = (m*v^2)/2 + m*g*h

For simplicity, we choose mass as 1 kg, h = 300km, v = 1st cosmic velocity =~ 7100m/s

1*7200² + 1*9.81*300x10^3 = 2.8148x10^7 [Joule]

Potential Energy is some 10% of the total energy. As this is for one kg of mass, and m goes linear in the above equations, you can scale with the mass of your satellite.

Energy at 36000 km:

Speed from radius and time for one orbit (1 day=84600 sec) v = 2*r*pi/t = 2*36x10^6*3.14159265/84600 = 2673.7 m/s

E_kin + E_pot = (m*v^2)/2 + m*g*h = 3.57x10^6 + 3.53^8 =~ 3.56×10^8 [Joule]

Now kinetic energy is only about 1% of the total energy!

A LEO has about 8% the energy of an GEO. The satellite needs 3.29x10^8 J/Kg Energy to get from LEO to GEO.

Lets say it's 10kg and has 50 W of power for thrust. 3.3x10^8 * 10 = 3.3x10^9 J thrust

1 Joule is 1 Watt / 1 second, 1 Watt second = 1 Joule 1 Watt day = 84600 Joule = 8.46x10^4 Joule

Our 50 Watt ion drive can increase the energy by 4.23x10^6 Joule a day. How much days will LEO to GEO take:

We have some 10^8 divided by some 10^6, it's a matter of months, the calculation says 77.8. But we should be satisfied to get an order of magnitude after the rough assumtions and estimations made before. If I made a mistake above, maybe this is off by an factor of 10, then it's 2 year. Still fine!

Of course you have to count in the gas you want to ionize, which reduces the weight over time (but I was really bad at differential equations and would not get that right), and maybe the weight and power estimations are not very realistic, and using steady thrust instead of short impulses decreases efficiency in orbit changes, and changing from polar to equatorial orbit takes extra energy, and maybe an elliptic orbit takes less energy, and maybe some inaccuracies more. But this does not matter:

In the end, it seems that changing from LEO to GEO or HEO is possible in sensible time.

Regards

Patrick

(*) Disclaimer: This is High School maths, please double check and correct my calculations -- Engineers motto: cheap, good, fast: choose any two Patrick Strasser <patrick at wirklich priv at>

On 04/29/2013 03:50 PM, Patrick Strasser wrote:

Speed from radius and time for one orbit (1 day=84600 sec)...

Uh, 86400 sec... But the difference isn't particularly significant.

--- On Tue, 30/4/13, Nick Pugh [email protected] wrote:

From the comments HEO is challenging but doable. So let's get started.

But Nick it is already started, several groups have already developed CubeSat ion motors.

The fact that, as far as I'm aware, none of the groups that have developed Ion Powered CubeSats are anywhere near launching yet shows us where the big road-block is - the lack of cheap launches.

As I see it there are three key things that need to be developed and proved in Space: 1. Large deployable CubeSat solar panels (although NEE-01 Pegasus just launched has this, be interesting to see how it performs) 2. Ion motor 3. Deployable CubeSat antenna's - if you're putting a CubeSat above 7200 km you could do with something more than a dipole, but what would you have ? and would there be issues with having both a large deployable solar array and deployable antennas.

bring up this idea at Dayton. I noticed that none of the board of directors of AMSAT have commented on this thread. If we want to go to HEO we will have to speak a little louder

I sincerely hope BOD continue to fulfill with their existing commitments rather than overstretching limited resources. But there's nothing stopping individuals experimenting with and developing the necessary technologies Deployable panels/Motor/Antennas themselves. After-all the early OSCARs were created by very small groups of people who just went out and did it.

73 Trevor M5AKA

Well I did a rough back of the envelope calculation for the time required to accumulate the energy necessary to get from LEO to HEO, but there are a lot of details that still need to be calculated. And the devil is in the details. But this will get things started

The difference in orbital energy between a LEO and GEO is about 25 MJ/kg. So, for a 10 kg nano sat, we would need to supply at least 250 MJ. Now I suspect that when all is said and done, it cannot be done for that, but I haven't done any detailed orbital transfer calculations.

OK, suppose we have Nick's 50 Watt solar panel, and lets also say that initially half of that power can be put into propulsion, the other half being needed for navigation, housekeeping, comm, and telemetry. You could probably get away with more for propulsion.

So say we need to generate at least 250,000,000 (it is probably more) Joules of energy to get from LEO to HEO. The solar panel can supply 25 Watts or 25 Joules per second. so it will take 10,000,000 seconds to generate the 250MJ required.

Now the satellite is only illuminated for roughly half an orbit, so we need to double the time to 20,000,000 seconds on orbit. Now there 31,536,000 seconds in a year, so it would take 231 days to accumulate the minimum amount of energy to get to GEO.

Well, I neglected inefficiencies in the system, such as the ability of the ion-thruster to convert electricity into thrust and how efficiently the batteries or capacitors can be charged and store energy. I also ignored the drag at lower latitudes, which may be considerable. I suppose that one could only operate the thrusters while the spacecraft is illuminated and that would eliminate the storage problem. Say the whole system is 50% efficient, and I am guessing here, that would make it 462 days, or 15 months.

I suppose that whether or not that is a long time, depends on your point of view. I'll bet if the transfer burn strategy is calculated it gets even worse. Things seldom get better. You can't do a simple Hohmann transfer, but would need to do multiple burns, or a continuous burn over the illuminated part of the orbit. I suppose that would produce an orbit that is not really circular at any given time but it might all average out over all the burns. A constant burn may be more efficient in terms of energy use that a Hohmann; I don't remember. I do remember that one wants to burn at apogee to get the biggest bang for the buck, and I suspect that the illuminated portion of the orbit is not always at apogee, so the energy will not be used efficiently.

Now a GEO orbit, while a desirable goal, is not necessarily what is needed for amateur radio communication. Something short of GEO, and even elliptical would still be useful and only require repointing of the antenna from day to day, and perhaps hour to hour at Apogee. Orbits significantly higher than LEO, but lower than GEO are also very useful. Compare for example the available time per pass between ISS and AO-7, and for that matter the RS10, 11, 12 and 13 birds.

One would need to plan how to go through the Van Allen belts, as with such a slow burn one would spend a lot of time where the radiation is high.

All of this is not meant to be a rigorous calculation, but rather just an indication of whether it is reasonable, and if it is worth pursuing further. It does to seem to be within the realm of possibly, and probably should be pursued further, at least until a real show stopper shows up. - Duffey KK6MC

-- KK6MC James Duffey Cedar Crest NM

On Apr 28, 2013, at 3:34 PM, Franklin Antonio [email protected] wrote:

At 11:14 AM 4/28/2013, Nick Pugh wrote:

...

I have just returned from a satellite conference and I think new technology will now give us a path to HEO.

I've thought for a long time that ion engines (small thrust pushing for a long time, powered by electricity) could be of great value to us.

Has anyone done the calculation to see how long it would take to go from LEO to HEO with an achievable ion engine? This seems like the first thing to calculate. If it takes less than 1 year, it seems worth serious investigation.

There are many other hurdles, of course, such as attitude control (keeping solar panels pointed at the sun while at the same time keeping engine pointed in the direction we want thrust, over a long period of time). The schemes and compromises for these issues can be worked if the basic thrust math works out.

N6NKF

---

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