Brian Wang has Started Writing Some Regular Articles for Universe Today

I will be writing some regular articles for Universe Today. Of course, I will still be writing my regular amount of Nextbigfuture articles. I will write about once per week over at Universe Today. My first article is about the most promising ways to start traveling faster than 1 million miles per hour. This is for larger spacecraft and not just ultra-light sails.

The top two projects are the laser-powered lithium-ion drive and the positron catalyzed fusion drive. Both have NASA NIAC funded projects right now.

The US military is spending billions to enable combat lasers. Those lasers will reach megawatt and multi-megawatt arrays.

The Lithium-ion drive will have 50,000 ISP. This is 100 times more than chemical rockets and ten times more than current ion drives. NASA Jet Propulsion Labs (JPL) will prototype the first 50,000 ISP lithium-ion drive within 4 months.

The design will power-beam 6000 volts of megawatts of energy around the solar system. This will enable direct use of the power for the lithium-ion drives. This will keep the system low weight with high acceleration.

The positron catalyzed fusion system design avoids all of the huge problems with achieving antimatter or fusion drives.

The huge problems are being unable to produce, store or use antimatter.

The positron or anti-electron approach uses isotopes (Sodium or potassium) which naturally produce positrons. Isotopes can be bred in a process similar to uranium breeder reactors. Neutron sources are used to make more isotope.

There is no storage of antimatter or anti-electrons. The propulsion system will use the positrons immediately.

14 thoughts on “Brian Wang has Started Writing Some Regular Articles for Universe Today”

  1. People have been making positrons for a long time. I don’t think there’s any experimental evidence they can catalyze fusion.

  2. Congratulations, Mr. Wang.

    I especially like the idea of low-dispersion wavelength-optimized laser-PV energy transfer systems for propelling large spacecraft to significant velocities.

    It is so important to keep in mind Tsiolkovsky’s Rocket Equation though. It is simple, it gives an idea of the limits of what can be achieved, and what NEEDS to be developed for various exploration objectives.

    ⇒ ΔV = 9.81 ISP ln( M₀ / M₁ );

    Pretty simple equation to explain (thus remember)… 9.81 × ISP is the conversion of ‘standard form’ ISP (measured ironically in ‘seconds’) into newtons-seconds-of-thrust-per-kilogram-of-reaction-mass. 9.81 is the force of Earth’s gravity. M₀ is the starting mass, and M₁ is the ending mass.

    Anyway, this in turn then can be inverted to find the necessary ISP to achieve a given ΔV and so forth, almost trivially.

    ⇒ ISP = ΔV / ( 9.81 ln( M₀ / M₁ ) );

    So, lets say we have a spacecraft that is 75% reaction mass such as lithium metal, which in this article is to be vaporized, ionized and shot out the ion-engine as high velocity ions. M₁ = ¼ M₀, right? Because Fuel = ¾ M₀. So, (M₀ / M₁) → (1 ÷ ¼) → 4. If we want a ΔV of 500 km/s (over 1,000,000 MPH), then:

    ⇒ ISP = 500,000 / (9.81 ln( 4 ));
    … ISP = 36,800;

    So there you are. Without spalling off spent housings and so on (like the multiple stages of a conventional rocket), you’d need the lithium to have an exhaust velocity of 9.81 × 36,800 → 360,000 m/s or so. Working with the kinetic energy equation (for m = 1 kg)

    ⇒ E = ½mv²
    … E = 0.5 × (9.81 × 36,800)²
    … E = 65,000,000,000 J/kg

    That is a HUGE number, but not in the context of hours, or days instead of seconds. If our putative laser-energized ion-propelled rocket can receive a megawatt of laser power, and if it is about 25% efficient at converting it from light to fast-moving ions, then:

    ⇒ ion energy = 1,000,000 W × 25%
    … ion energy = 250,000 J/s

    ⇒ ion mass = ion energy / specific energy (from above);
    … ion mass = 250,000 J/s ÷ 65,000,000,000 J/kg
    … ion mass = 3.84 mg/s

    And

    ⇒ thrust = ion mass × 9.81 × ISP
    … thrust = 3.84×10⁻⁶ kg × 9.81 × 36,800
    … thrust = 1.4 N

    Not much thrust. Oh well. It really is the problem of HIGH ISP reaction mass propulsion. While the ultimate velocity of the spacecraft is high (500 km/s), the energy investment is prodigeous.

    Just saying,
    GoatGuy

  3. why not make heavy water onboard with free space radiation…water…use it as a shield…over time…heavy water reactor…

  4. Congratulations, Mr. Wang.

    I especially like the idea of low-dispersion wavelength-optimized laser-PV energy transfer systems for propelling large spacecraft to significant velocities.

    It is so important to keep in mind Tsiolkovsky’s Rocket Equation though. It is simple, it gives an idea of the limits of what can be achieved, and what NEEDS to be developed for various exploration objectives.

    ⇒ ΔV = 9.81 ISP ln( M₀ / M₁ );

    Pretty simple equation to explain (thus remember)… 9.81 × ISP is the conversion of ‘standard form’ ISP (measured ironically in ‘seconds’) into newtons-seconds-of-thrust-per-kilogram-of-reaction-mass. 9.81 is the force of Earth’s gravity. M₀ is the starting mass, and M₁ is the ending mass.

    Anyway, this in turn then can be inverted to find the necessary ISP to achieve a given ΔV and so forth, almost trivially.

    ⇒ ISP = ΔV / ( 9.81 ln( M₀ / M₁ ) );

    So, lets say we have a spacecraft that is 75% reaction mass such as lithium metal, which in this article is to be vaporized, ionized and shot out the ion-engine as high velocity ions. M₁ = ¼ M₀, right? Because Fuel = ¾ M₀. So, (M₀ / M₁) → (1 ÷ ¼) → 4. If we want a ΔV of 500 km/s (over 1,000,000 MPH), then:

    ⇒ ISP = 500,000 / (9.81 ln( 4 ));
    … ISP = 36,800;

    So there you are. Without spalling off spent housings and so on (like the multiple stages of a conventional rocket), you’d need the lithium to have an exhaust velocity of 9.81 × 36,800 → 360,000 m/s or so. Working with the kinetic energy equation (for m = 1 kg)

    ⇒ E = ½mv²
    … E = 0.5 × (9.81 × 36,800)²
    … E = 65,000,000,000 J/kg

    That is a HUGE number, but not in the context of hours, or days instead of seconds. If our putative laser-energized ion-propelled rocket can receive a megawatt of laser power, and if it is about 25% efficient at converting it from light to fast-moving ions, then:

    ⇒ ion energy = 1,000,000 W × 25%
    … ion energy = 250,000 J/s

    ⇒ ion mass = ion energy / specific energy (from above);
    … ion mass = 250,000 J/s ÷ 65,000,000,000 J/kg
    … ion mass = 3.84 mg/s

    And

    ⇒ thrust = ion mass × 9.81 × ISP
    … thrust = 3.84×10⁻⁶ kg × 9.81 × 36,800
    … thrust = 1.4 N

    Not much thrust. Oh well. It really is the problem of HIGH ISP reaction mass propulsion. While the ultimate velocity of the spacecraft is high (500 km/s), the energy investment is prodigeous.

    Just saying,
    GoatGuy

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