The Case for Space V: Lightcraft

Lightcraft
1. Description
2. Advantages
3. Disadvantages
4. Economics
5. Summary


1. Description

In section 2 of my original blog post, "The case for space", I discussed several low cost launch systems. Of these systems, all save one (Nuclear Pulse Propulsion) had something in common: the launch vehicle did NOT carry its own propellant.

The lightcraft concept follows in this vein. It uses lasers to heat air under the vehicle so violently that it "explodes." These explosions (hundreds or thousands of them per second) lift the vehicle into the air and accelerate it on its trajectory. In this concept, the atmosphere becomes the propellant and the laser provides the energy. This type of engine differs greatly from a traditional rocket in which the propellant supplies both the reaction mass and the energy to heat the propellant.

The lightcraft concept ensures that the air between the laser aperture and the vehicle doesn’t absorb this energy by shining a relatively diffuse laser beam from the laser and off of the ground mirror. However, the underside of the launch vehicle consists entirely of a parabolic mirror that focuses the laser beam into a small area under the vehicle. The heating caused by this focused beam breaks the air down into a plasma. The plasma absorbs the laser light far better leading to the detonation.

Here’s a diagram of how the system works:




And here’s another picture of one in operation:

Lightcraft test article in flight

and a video of the test article in operation (note they spin the article up for gyrostabilization):

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2. Advantages

This lightcraft concept possesses many positive attributes and is in many ways the best of all possible solutions.


Reusable launch infrastructure
In conventional space launch concepts (e.g. rockets) the majority of the equipment (e.g. the rocket stack) created to launch vehicles into space is consumed in every launch. This means that every launch has to rebuild this expensive high-tech vehicle for every launch.

The lightcraft does not suffer from this problem. All of the expensive pieces of infrastructure (power, laser, and mirrors) are left on the ground where weight is not a problem and it won’t be thrown away after each launch. The vehicle itself can be made of inexpensive aircraft materials (typical aerospace aluminum alloys or carbon composites - depending upon the payback).


Doesn’t have to carry its propellant
Since the lightcraft doesn’t carry its propellant (or only carries a small amount), nearly every pound lifted will be payload and not burned up. It also means the amount of power is far smaller than that required for launching similar payloads via conventional launch systems.


No turn-around time
Unlike EVERY other launch infrastructure currently used, the use of the lightcraft relies only upon the availability of launch vehicles and the amount of power available. Meaning as soon as one craft has finished its launch, the next vehicle can be launched immediately. The only limit is power.

Ironically, developing this infrastructure would be a GREAT use for wind power! Wind power is hard to predict. Sometimes it under produces, other times it over produces. A launch facility wired into this grid and located in California could consume all of the excess wind power significantly easing the problems encountered by the electric companies in that state.

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3. Disadvantages

This concept still suffers from a few difficulties; however, most of these have relatively simple and straight forwards solutions.


Stability
Getting the vehicle to ride on top of this laser beam will be about as stable as trying to stand a pencil on its tip - meaning it’ll be very difficult.

The simple solution is to spin the vehicle at high speed and this was done for the test - spinning the vehicle at 13,000 RPM. This kept the vehicle stable for the entire test flight (15 seconds). A larger vehicle would keep spinning longer so this needs to be considered but shouldn’t pose a severe problem. Besides more complex solutions such as gyroscopes or attitude jets could also be utilized.


Laser focus
Light diverges, even laser light. As the vehicle climbs away from the lasers, the laser beam diverges - meaning eventually the beam gets larger than the vehicle and some of the laser’s energy isn’t captured for propulsion under the craft. If too much energy is lost, the craft won’t make orbit.

The simple solution is to use a larger mirror. A larger mirror, say 30 cm (slightly more than 1 foot) should be able to focus optical frequency lasers onto a spot a shade more than 1.6 m (5 feet) out to a range of 800 km.

This only accounts for the beam spread in a vacuum so some other technology also needs to be incorporated to account for the thermal bloom caused by the laser moving through it. The technology best able to correct this problem is called adaptive optics. Adaptive optics are used now in major telescopes to get crystal clear pictures of space.

In both cases, note that these solutions already exist and are not stumbling blocks to deployment.


Orbit circularization
The lightcraft depends entirely upon the atmosphere as the vehicle’s propellant. The "push" provided by those explosions vanishes completely after it climbs out of the atmosphere. Unfortunately every spacecraft needs a final push to circularize its orbit once it reaches the right height.

The simple solution is to provide a small rocket engine to provide this final push. Perhaps a better solution is to provide a small tank of water (or denser easily handled liquid), which would be dumped and the illuminated by a set of final parting shots by the launch lasers. Each of these solutions requires no technological breakthroughs and is well understood.


Burning up satellites
As part of launching the lightcraft into space, we’ll be shining 1 megawatt of laser light per kilogram of materials launched. Meaning a 1000 kilogram (metric ton) craft will have 1000 megawatt lasers shining on it! Even a slight miss by a small fraction of this energy could easily fry any satellite it hits.
Most satellites currently in orbit around the Earth orbit at an inclination of 23.3 degrees, which is the latitude of Kennedy Space center (because that’s the easiest orbit for those launches to achieve). The simplest solution is to locate the lightcraft launch facility slightly north of this latitude. Then a little bit of management of launch times should be sufficient to ensure no satellites are overhead during launch times.

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3. Economics

According to Wikipedia, the studies performed in 2000 showed a 1 kg payload could be launched into space for about $20 worth of electricity. Since greater than 85% of all of the infrastructure would remain on the ground (current space craft launch better than 85% into space where it is never recovered), depreciation of the launch infrastructure might consume only another $40 per kg. Assume that operations require another $20 per kg. In total we could actually see a launch cost around $100 / kg (or about $40 / pound). This is about 1/40 to 1/100 the current launch costs!

What this means is that the rate of payback on the system depends mostly upon the rate of launches. The launch vehicles will be (relatively cheap), while the lasers and mirrors remain on the ground. The vehicles carry very little propellant and that can be water - requiring no special handling or safety requirements.

Finally many of the problems (such as focusing laser beams) actually get easier to resolve when using a larger vehicle. A 1000 kg payload vehicle doesn’t need mirrors as large as a 1 kg vehicle but it will require more mirrors and lasers.

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5. Summary

Positive attributes of craft	LC	LGG	RA	NPP	NR	FFR	CR
Most equipment reused?	Yes	Yes	Yes	Yes	Yes	Yes	No
Doesn't carry its propellant?	Yes	Yes	Yes	Yes1	No	Yes1	No
Rapid turn around?	Yes	No	No	Yes	No	Yes4	No
Safe for nearby craft?	No	Yes	Yes	No	Yes	Yes	Yes
Can use cheap materials?	Yes	Yes	Yes	Yes	No	No	No
Requires no breakthroughs?	Yes	Yes	No	Yes	Yes	No	Yes
Gentle acceration3	Yes	No	Yes	Yes	Yes	Yes	Yes
Large payloads (>50 tons)	No	No	No	Yes	Yes	Yes	Yes
Interplanetary flight	No	No	No	Yes	Yes	Yes	Yes
Space launch	Yes	Yes	Yes	Yes	No	No	Yes
Estimated launch cost per pound	<$500	<$500	$500	<$5002	N/A	N/A	>$10,000
Score	7	6	6	9	6	7	6

• LC – Lightcraft
• LGG – Light Gas Gun
• RA – Ram Accelerator
• NPP – Nuclear Pulse Propulsion
• NR – Nuclear Rocket
• STS – Space Transportation System aka Space Shuttle

1. Nuclear pulse propulsion has such good performance that this really isn't a drawback for that concept.
2. I'm making a WAG (wild @$$ed guess) at this because I have no idea how much nuclear bombs cost.
3. This is a measure of whether the system could be used for manned vehicles. Many of these systems can be tuned to provide different accelerations. However, the light gas gun would leave people as squished jelly in the bottom of the launch vehicle.

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Proceed to my next blog, Case for Space VI: the light gas gun


Return to my previous entry, Case for space IV: How to pay our way

Computers: Fighting spyware

In my last blog, computer maintenance, I discussed some basic computer maintenance tasks. After you take care of those tasks you should ensure that you’ve cleaned off any potential malware.


Spyware
1. Introduction
2. An ounce of prevention
3. Spyware Blaster
4. Spyware Search & Destroy
5. Web of Trust


1. Introduction

Malware (a word coined to encompass all software which might inhabit your computer against your wishes) has become pervasive on the internet.

Some of the anti-malware software providers leave unprotected “bait” computer computers on the internet to see what it catches in the wild. They’ve discovered a computer gets “attacked” within just a few minutes of hopping onto the internet. Even worse unprotected computers are often compromised within 10-20 minutes!

Malware affects the stability of your computer, slows its performance, but worse it often seeks to steal your personal data. This data is sold to the highest bidder and is used to steal your ID and take out credit cards in your name.

With just a little time spent on a one-time set up, you can set up your computer to automatically update its anti-virus, anti-spyware, and run scans.

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2. An ounce of prevention

First of all, you need to be aware that many malware attacks involve “social engineering,” which is a fancy way of saying “tricking you to install something you don’t want.” To avoid this type malware, don’t go to web sites you don’t trust, don’t open files in email unless they are attachments you expect, and don’t follow links provided in your emails especially to banks and other sites. Let me reiterate that last one, whenever you wish to do online banking or credit card transactions you should always type in the address or get there from a saved link.

Next you should install basic protection for your web browsing. I use multiple products to help fight for me. These include:

Spyware Blaster
Spyware Search & Destroy
And another Firefox addon called Web of Trust

Download this software and then run their install images. I’ll address the details of each piece of software in a separate section.

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3. Spyware Blaster

1. Launch the software
2. Click on the “Updates” link on the left.
3. Then click on the [Check for Updates]
4. Once the update completes, click on the “Protection Status”
5. At the bottom of the page, select the “Enable All Protection”
6. That’s it!

This application does no scans or malware removal. Its only purpose is to protect you from your own web browsing.

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4. Spyware Search & Destroy

1. Launch the software
2. After Spybot – Search & Destroy launches, click on the [Search for Updates]
3. When the update dialog pops-up, leave the selected site alone and click the [Search]
4. Make sure all updates are selected and click on the [Download] button.
5. Wait for the update to complete.
6. When finished, click on the [OK] button.
7. In the main Spybot – Search & Destroy window, click on the “Mode” menu -> select “Advanced Mode”
8. In the left pane of Spybot – Search & Destroy, select “[+] Tools”
9. In the main window, check all tool check boxes (we want to have access to all of these tools)
10. In the left pane of Spybot, select the “Resident” tool
11. Ensure both (SDHelper & TeaTimer) Check boxes are checked (see the note on TeaTimer below)
12. Click on the “ActiveX” tool
13. One-by-one click on each registry entry that does NOT have a green check mark.
14. Examine the information for these entries and delete all entries which you do not understand. You delete these entries by highlighting the entry and clicking on the “X Remove” pick at the top of the page.
15. Click on the “BHOs” tool.
16. Examine the information for these entries and delete all entries that you do not understand. You delete these entries by highlighting the entry and clicking on the “X Remove” pick at the top of the page.
17. Click on the “IE tweaks” tool.
18. Ensure the “Lock Hosts file read-only as protection against hijackers” check box is checked.
19. Click on the “Hosts File” tool.
20. At the top of the page, click on the “+ Add Spybot-S&D hosts list”. This will prevent you from navigating to a page which is known to transmit malware.
21. Now click on the “[+] Settings” bar in the left pane.
22. Click on the “Scheduler” tool
23. At the top of the page, click the “+ Add” button.
24. Select the “Schedule” tab, click on the [New] button, enter frequency (weekly), start time (when the computer will be on but not used), pick a day of the week (any).
25. Select the “Settings” tab, choose any settings that seem appropriate but I do recommend clicking on the “Wake the computer to run this task” check box to ensure your scan happens.
26. Click the [OK] button.
27. You will be prompted to enter the username and password of the account that should run this scan, enter the administrators username and password.
28. Click the [OK] button.
29. Click on the “+ Add (Updater)” and repeat steps 24-28 with the exception that I’d recommend running the updater daily.
30. Click on the “[+] Spybot-S&D” bar in the left pane.
31. Click on the “Immunize” tool.
32. Spybot S&D will ask you to close your browsers – do so, and click on the [OK] button.
33. Wait for the immunization check to complete (it’ll show you that you need to immunize your computer).
34. Click on the “+ Immunize” button at the top of the page. Wait for the browser immunization to complete.
35. Click on the “Search & Destroy” tool.
36. Click on the “Check for problems” button at the top of the screen.
37. Wait for the check to complete.
38. If Spybot S&D finds problems, they’ll appear as checked entries. Click on the “Fix Selected” button at the top of the page.
39. That’s it. You’ve updated Spybot S&D, scheduled to automatically run on its own, and performed your own scan.

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5. Web of Trust (WOT)

Web of Trust is a web site rating tool. Rated web sites should have a ring rating next to their links. Untrusted sites should have red rings. Trusted sites should have green rings. Unrated sites could be safe or not. I highly recommend avoiding untrusted sites, these have been known to sell user information or worse.

To install WOT:
1. Launch Firefox
2. Click on the “Tools” menu.
3. Select the Add-ons pick
4. Type “WOT” into the upper left “Search” window and hit your enter key.
5. You will probably need to hit the “See all results (#)” link at the bottom of the page.
6. You should see the “WOT – Safe Browsing Tool”, click on the “(+ Add to Firefox)” button to download the software.
7. The Software Installation dialog should appear. Wait for the 5 second countdown timer and click on the [Install Now] button.
8. You will be prompted to restart Firefox, so do this now.
9. Congratulations! You have installed Web of Trust!
10. If this is your first installation, you will be prompted to subscribe to a WOT list. Select one geographically close to you.

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Proceed to my next computer blog, Antivirus software.

Return to my previous computer blog, Computer maintenance.