Why Ghana Started a Space Program | Hacker News Reader

Why Ghana Started a Space Program

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66 pointscpeterso42 comments

Good for them. I think putting a cubesat to orbit is under $100k these days.

Was thinking an EM railgun (either from ground or from a plane flying as high as it can) could probably put a nanosat type payload to orbit for much less.

My guess is there will be a lot more satellites (and eventually debris) in orbit in the coming decades.

I like the railgin idea - is there any studies on this?

Ok, downvotes. "are there any studies"?

I think railguns are better at sending dumb payload masses, there's a fairly high amount of electricity pumped into the rails and IIRC the military ones have a sort of plasma muzzle flash effect.

Cubesats tend to be lightweight and small, and probably wouldn't survive the launch.

Aha - sounded too good to be true.

I suppose it depends on how fast we accelerate them upto right speed

So if we imagine a Nimrod style dish on top of an aircraft near space, and say orbital speed is 30Mach or about 21,000mph call it 30kph for ease, and minimum useful weight would be 500g we need to input ... 54MW?

And control travel around a dish tighter than anything previously seen.

Yeah - nice idea ...

It's a little more complicated. A railgun launch would see the payload moving at above orbital velocity immediately upon leaving the gun, creating serious aerodynamic headaches (drag). Rockets don't accelerate to such speeds until well above most of the atmosphere. For a tiny/lightweight object like a cubesat, the drag climbing up from the surface will be monumental.

It's a trap. Drag requires more speed, which creates more drag. So you go with a heavier, more aerodynamically efficient object, which requires a larger railgun. The minimum size for this railgun is probably so large as to make the entire endeavor futile in comparison to rocketry.

Artillery gets around this by firing relatively high. This wouldn't be practical for launch to orbit where you want as much momentum as possible laterally rather than vertically.

The engineering required for an orbital launch gun is beyond the scale of anything yet built.

Let's say, for the sake of argument, that your space gun's acceleration track climbs the slopes of Chimborazo in Ecuador and releases the launch vehicle at the summit.

From there, if you launch eastward, you get about 460 m/s for free from the rotation of the Earth near the equator. LEO requires about 7800 m/s. Earth escape requires about 11180 m/s from that altitude.

So if you go to LEO, you need another 7340 m/s of velocity. If you accelerate at 3 g, your track needs to be 920 km long. That isn't quite the distance from the end of your track to the Galapagos Islands.

The same length of track could hit escape velocity with constant acceleration at 6.5 g.

For reference, the Large Hadron Collider is 27 km in circumference, and cost about $5 billion. A space gun would be 34 times longer, and portions of it would have to be evacuated and neutrally buoyant at some depth under the ocean. The entire length would need to be powered.

If you built a circular track 920 km in circumference, 147 km radius, the centripetal acceleration required to keep something moving at 7340 m/s on that track would be more than 37 g. That only increases as you reduce the radius. So no getting away with a shorter track.

Why only 6.5g? This isn't launching hamsters. Numbers like 100 or even 1000g are an option when dealing with tiny sats. There is already a small industry surrounding building electronics capable of being fired from artillery guns.

That's just the minimum required acceleration to hit Earth escape velocity (at the peak of that mountain) with a track of that length.

If you're going to build a megastructure like this, you might as well make it capable of launching manned vehicles. If your typical payload can handle 1000 g, you wouldn't need anywhere near that length of track. You would only need 3 km or so, I think.

A 3 km long coilgun is possible with today's technology.

This may be a stupid question, but why not do 2 stages, like today ? The railgun replaces the first stage but there's a second stage, like today, that gives all the lateral velocity.

Stage I of a Saturn V contributes a maximum of about 3600 m/s of delta-v. Replacing a first stage of that magnitude would require a 3g acceleration track 220 km long.

It still takes a lot of launches before the track starts to be cheaper than just building a new first stage for each launch. It takes a lot more if the first stage rocket is reusable.

There has been documented tests of railguns launching raw material around those speeds (https://en.wikipedia.org/wiki/Railgun#Tests). As the sibling comment said, there's no reason to limit ourselves to 3g (yet), and indeed someone laid out a plan to launch material to space with a railgun, where the first "stage" would be a railgun and the second stage would be a traditional rocket (https://en.wikipedia.org/wiki/Railgun#Launch_or_launch_assis...). It says that acceleration can reach a little less than 2000g. Unfortunately I haven't found any realization of this.

I think there are many variations on the idea that have been proposed, e.g. StarTram [1].

Wikipedia in general is a good starting point to look at some of the launch methods proposed over the years [2].

[1] https://en.wikipedia.org/wiki/StarTram

[2] https://en.wikipedia.org/wiki/Non-rocket_spacelaunch

You can't put anything in orbit with a railgun. You can replace a huge fraction of a rocket with one, but you can't reach orbit by it alone.

Also a railgun that fits an airplane would crunch the satelite.

A company in the UK is working on a multithrust rocket/launch vehicle that would be reusable. It mixes a super-cooled jet engine with a rocket booster. For once you get beyond enough air pressure for the jet engine.

https://en.wikipedia.org/wiki/SABRE_(rocket_engine) https://en.wikipedia.org/wiki/Skylon_(spacecraft)

Something like this, that's reusable, would allow small (but larger than cubesat) payloads into orbit for what should be a reasonable price. 200 launch lifetime on the vehicle is the plan.

Seems like a really interesting idea. For now I've got my money on SpaceX in terms of decreasing the cost to orbit first, they have the hardware already up and flying, and it's a bit less exotic so the engineering issues may be more well understood.

I agree, I think SpaceX will have re-usable rockets with the Falcon 9 long before this is working. But I believe you could extend the jet-powered-rockets to larger launch vehicles than you could the tech in the Falcon 9. Plus, the tech might be able to be extended to have cheaper super-sonic flights. But that's long ways down the road.

I agree, it's quite an exciting proposition if we can get a real space plane.

If SpaceX can recover and re fly the booster staging as they hope to, we should see a marked decrease in cost to LEO. According to their numbers, the booster and engines clock in at 16 million dollars. Normally that's a sunk cost every single launch, so even in a scenario where they fail to recover nearly 50% of the rockets, (they believe they can achieve <95% recovery eventually) the cost to orbit could fall by almost half in the immediate future.

The reason I'm excited about this is that the really hard part (flipping a booster that's going 8,000 KPH around and flying it back to the landing zone) has worked pretty consistently. There have been several technical issues with the actual landings, I think they are 1 for 4 now but what people tend to forget is that that portion of the process is something we've done with rockets since the 60's - it's how we got down to the lunar surface.

Space Exploration can be debated, but launching Satellites, every country should be able to do it.

Why should every country be able to launch satellites? There are many countries which have no sea ports, yet they all need space ports?

Those landlocked countries do need sea ports too. It's just a bit harder to do anything about that without invading your neighbours.

No - they need access to sea ports which can be done easily via trade. Likewise they need access to satellites which also can be accomplished through trade.

Honestly, the spectrum around here.

You knows what's better than having someone else's removable permission to use their sea ports at their convenience on their terms? Having your own sea ports.

Although even better than that is to sell your sea ports to a corporation and then rent them back at fair value in order to improve the country's finances.

Should have the ability to build satellites and if geography permits should be able to launch them

Apologies for being repetitive, but you didn't answer my question. Why does a country need to be able to build and/or launch satellites? I really can't see any reason for it. There are many countries with little or no shipbuilding and/or port capabilities.
Switzerland has done very well without a sea port, and I cannot imagine why any country needs satellite capabilities (aside from nationalism).

The advantages of Earth observing satellites in the arena of - telecommunications - navigation & mapping - meteorology - agriculture, mining etc. things that are part of both defense and commerce.
>>and I cannot imagine why any country needs satellite capabilities (aside from nationalism).<< GPS ?

There is a strong case for there being satellite and launch providers/provisioners; this does not mean that every country needs their own.

There are some tiny 'countries' out there. If you can see the surface area of your country from a blimp then launching a satellite seems wasteful ex: Monaco, Nauru.
I am sure Liechtenstein could do GPS from blimps / drones cheaper that even microsatellites, but why build your own receiver when GPS is cheap and your to tiny to matter militarily.

You can buy such services using existing satellites, or buy the designing, manufacturing and launching of such a satellite - there's no inherent need for everyone to do all the steps domestically.

http://swisscube.epfl.ch/

Did you read the article? They stated very specific reasons why they needed satellites. Things like monitoring deforestation, farmland, weather, etc.

Needing to have satellites and needing indigenous design/build/launch capabilities are very different. Most satellite users do not design, build, or launch their own satellites.

I don't know about every country, but the article lists some important reasons for Ghana to have the capability, namely combatting illegal mining and assistance with disaster relief.
At the moment Ghana is reliant on foreign satellites, which aren't necessarily available when needed.

Just because you don't have sea ports doesn't mean you can't have boats under your flag.

Every country should be able to build cars, too, but most of them don't because it doesn't make sense. It takes a whole lot of time and money to develop that kind of capability.
And it makes other countries nervous. Anything that can be used to launch a satellite can be used as an ICBM.

Ghana is at an interesting position vis-a-vis UK.
We are on the same time zone, and there are about five daily flights between london, which has what anecdotally feels like a big Ghanaian population.
I am not sure where I am going with this other than if Ghana was a stock, she would be a strong buy.

Ghana does have a stock exchange so if you really believe and not just hope that Ghana is on the rise buy some stock - put your advice to the test.

Thank you. I shall

I hope to read a feel-good story on your blog about this in a few years' time.

Every time I hear of an underdog trying to introduce a space program I'm reminded of the anime Planetes and the pessimistic take it had on the issue.
But it would be great if Ghana did indeed stat a Space Program. We need at least one African country seriously trying to build a bridge to the stars.

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