Tag Archives: Space Settlement

Speaking in August at the 20th Mars Society Conference

I will be speaking at the August 23-26 Mars Society Conference at the Pasadena Convention Center.   This year will be another wonderful, informative convention with a new emphasis on VR projects we are currently getting ready to deliver for use at MDRS and eventually for Mars itself. We also have another university competition to design a heavy lander for Mars.

If you can’t attend the convention, I release the slides to this web site along with links to YouTube when The Mars Society puts those together a couple months later.

Planetary Protection and Settlement

On Thursday in the Science Track room at 1:00 PM, I’ll be speaking about finding ways for planetary settlement to work if and when life is found on another world.  This is actually highly likely given the amount of bacteria ejected into space from meteors colliding with Earth in the early days of the solar system after bacteria had already formed.  The issue is how to find a happy medium where we inhabit other worlds but we keep the existing biomes and our own habitats from interacting accidentally.

SpaceX, Methodologies, and Predictions

On Friday, I’ll be speaking at 2:30 in Room 214 on SpaceX and how the NewSpace companies are accelerating so quickly over their Legacy Space counterparts.  I’ll also forecast how some of these efforts will turn out based on past performance and current conditions.  Want a realistic estimate on when and where you will be able to fly around the Earth in a BFR for a family vacation?

 

Low-Thrust Breakthrough Propulsion Round-Up

Next Big Future has produced a number of articles recently on breakthrough propulsion.  Here is a summary of the current state of the art on these speculative systems.

Low-Thrust Propulsion systems are too weak to be used to launch from the surface of a planet, but have extreme efficiency and high exhaust velocities.  Basically, a space probe like Dawn had the propulsive force equivalent two sheets of paper held on your hand.  Yet it could thrust for years with this system.  Over the course of eight years, it thrust over 2000 days, with a change in velocity of 24,000 mph/ 38,000 kph.  That's more than it took to launch it into interplanetary space to begin with, and while using less than 937 pounds/425 kg of propellant on board.  Ion drive takes a slowly-released gas, gives it an electrostatic charge, and then accelerates it in a magnetic field and neutralizes the charge as it exits the engine.  Newer systems, such as the speculative EM-Drive, promise to work with no on-board propellant. 

While creating full-antimatter is very, very difficult and energy-intensive, making simple positrons (antimatter electrons) is fairly simple.  A group is working on a system that can fit on a cubesat for a demonstrator.  Rather than make full anti-matter atoms and trying to store them and use them later in an engine, a positon system is basically an ion drive system like Dawn uses, but using positrons made on the ship itself instead of ionized gas.  Positrons are naturally produced by radioactive materials.  So a sample of a radioisotope is placed on board, and the positrons it emits are cooled enough to allow them to be directed and accelerated in a magnetic field like in a conventional ion drive.  The resulting particles exit the vehicle at ten percent the speed of light.  If idealized, these systems could get to Mars in weeks, Pluto in months, and Alpha Centauri in 40 years.   The developer, Positron Dynamics, plans to launch a cubesat demonstrator somewhere between the middle of this year and next year.  The near term application of these motors would be as a more-efficient substitute for ion drive in positioning communications satellites.  In the longer term, they would be very useful for asteroid mining.  

To make a complex system a bit easier to understand, a small fuel pellet is compressed by a magnetic field and bombarded with particles.  It undergoes nuclear fission and the plasma is further compressed by the magnetic field.  The combination of compression and the heat, self-generated plasma magnetic field, and particle mix of the tiny fission explosion can trigger a fusion explosion, similar to the way an atomic bomb can trigger a thermonuclear (fusion) bomb.   As with the Positron example, this could theoretically get a vessel to Mars in a month.  It would generate exhaust ISP(the efficiency of a rocket)  of 30,000 seconds.   By contrast, a typical chemical rocket has an ISP under 450 seconds. 

This is similar to  EM drive, in that it depends on A) very tiny effects that can barely be observed and B) processes that defy conventional physics, but appear to be explained by some aspects of science.  When I say barely observable, we are talking 2 to 12 micronewtons.  A tiny bottle-rocket has 3 newtons of average thrust, or a million times as much as these experimental engines.  That said, they hope to get up to 10-20 millinewtons in a decade or two.  That said, a microthrust, propellantless system has no theoretical output limit, because there is no propellant to be used up.  This is why those who propose systems like this often speak of starships. 

Conclusions

The positron system seems quite logical, and can be demonstrated soon.  It has limits, though, because it relies on radioactive decay of highly radioactive materials.  This can be scaled down into tiny systems.   The PuFF system will require a lot of expensive research to get worked out, over a fairly long time period.  That said, it has a lot of similarities to Project Daedalus, and could be used for a simple starship probe eventually.  Such a system is at least a decade away, and would be quite large.  Mach Effect is a lot like EM Drive, but while the effects are more explainable, they seem to be even less powerful.   To power a vehicle with any velocity, it also has to be scaled up quite a bit.  
With new systems that can provide fission and possibly fusion electrical power coming online very shortly, systems that require lots of electricity (advanced ion drive, these propellantless systems, and so on) may be arriving sooner rather than later.  Expect to see something interesting in this range within five to ten years.  

Elon Musk on Reddit AMA

Elon Musk recently did a Reddit Q&A with members (Ask Me Anything).   This mostly focuses on details of the Mars vehicle update.  Here are some highlights.

Mars Settlement

  • The Mars city design from the video was mostly artistic (“I wouldn’t read too much into that illustration”.  There are no specific plans beyond propellant production, power, and life support.  He wants to enable other industries to go to Mars.
  • The landing sites need to be low altitude for maximum aerobraking.  Close to ice for propellant production and free of giant boulders.  Closer to equator is better for solar power.
  • SpaceX is building the ISRU (propellant production system) in house, and it’s pretty far along.
  • They plan to put communications satellites around Mars at some point.

Technical Details of the BFR and Spaceship

  • The vehicle would burn all the fuel in the main tanks getting to Mars (or the moon or Singapore or whatever).  It would then use the secondary tanks for landing.  In the case of Mars, it would turn the nose of the ship toward the sun and vent the outer tanks.  This would basically make the inner tanks super-cold for the trip.  (Editor note – it would also eliminate the possibility of spinning two spacecraft with a tether for artificial gravity).
    • They eventually will add a cryocooler (which would allow it to spin).
  • The newest Raptor engines being tested are actually sub-scale.  The final production version is being designed for reliability, not performance.
  • the small delta wing is to “balance out” the load on reentry, to keep the ship from entering engines-first.  It can also provide some pitch and yaw control during reentry.
  • The RCS system will be methane/oxygen and pressure fed.
  • Early versions of the tanker will be just a fully-loaded propellant tank ship with no payload.  Later versions will look “kinda weird”.
  • Heat shield tanks are mounted directly to the tank walls.
  • The development will start with a full-scale ship doing short hops of a few hundred kilometers up and across.  They don’t need the deep-space Raptor engines for that.
  • VERY INTERESTING – “Worth noting that BFS is capable of reaching orbit by itself with low payload, but having the BF Booster increases payload by more than an order of magnitude. Earth is the wrong planet for single stage to orbit. No problemo on Mars.”
    • Traditionally, methane doesn’t have the specific impulse to do single stage to orbit.
    • A BFS without the booster would be economical for domestic flights, in theory. They could also return themselves from interior destinations like Chicago to coastal launch facilities with the BFR stage.

Anyway, you can read it in detail if you like from the link above.  I simply gleaned what I could from the stream in the notes here.

Grand Challenges Part 2: Orbital Refueling

For every 25 kg of a fully-fueled launch vehicle, only 1 kg is payload to low earth orbit (LEO). For every 1 kg sent to Mars, there is 100 kg of launch vehicle mass. You want to get back from Mars? That’s another topic. With orbital refueling, it is possible to raise the payload ratio from one percent back to four percent, quadrupling the mass of the vehicle sent to Mars. Unfortunately, LEO is a risky place to have spacecraft lingering for long periods with large amounts of propellant on board. Fortunately, there’s a lot of progress being made recently in all these areas.

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