Pluto Orbiter – the Next Step after New Horizons

The spectacular success of the NASA New Horizons mission has led to many new discoveries about Pluto. The next step would be to send an orbiter. That isn’t easy to do with chemical propulsion but could be done with Direct Fusion Drive.

We’ve done a preliminary mission analysis for a Pluto orbital mission. We are baselining a Delta IV Heavy that can put up to 9,306 kg into interplanetary orbits. These plots show various parameters versus mission duration. The maximum duration is the same as the New Horizons mission, 10 years.

Let’s use the 4 year mission as a baseline. It would use a 2 MW DFD engine to reach Pluto in about 4 years and go into orbit. The engine would thrust for 270 days out of the 4 year mission producing 110 km/s delta-V. The trajectory is shown below

Once there, almost 2 MW of power would be available for the science mission, over 10000 times as much power as is available to New Horizons! The New Horizons bit rate is no more than 3000 bits per second. The high power would allow for a bit rate of over 135 Mbps for data transmission back to Earth using the JPL Deep Space Optical Communications System and a 30 kW laser transmitter. The time in transit is much shorter than New Horizons and would produce significant savings on operations costs. Launch times would be more flexible since gravity assists would not be needed.

DFD would use deuterium and helium-3 as fuels. Only 1700 L of helium-3 would be needed for this project. Current U.S. production of helium-3 is about 8,000 L per year.

Since we would be going all the way to Pluto it would make sense to include a lander. One way to power the lander is using laser power beamed from the orbiter. Here are results for a possible system, beaming over 30 Wh per pass from a 200 km orbital altitude.

Currently, experiments are taking place in the Princeton Field Reversed Configuration laboratory. Here is the machine in operation at the Princeton Plasma Physics Laboratory:

The next step is to build a slightly larger machine to demonstrate fusion. Fusion power generation has been demonstrated in the Princeton Plasma Physics Laboratory Tokamak Fusion Test Reactor and the Joint European Torus but never in a machine using helium-3. A flight engine would follow. Its small size would keep the development and production costs down.

DFD would enable many challenging missions include human exploration of Mars, Europa landers and interstellar probes.

Lunar Topography

If you are sending a spacecraft to the moon, you will be interested in lunar topography. A new function in the Spacecraft Control Toolbox lets you superimpose a height map onto any sphere.

The function RSHMoon.m gives you the Clementine spacecraft topographic data using a spherical harmonic expansion of the rangefinder data.

A new function, PlanetWithTerrain.m, lets you superimpose this data onto a sphere.

Maximum Achievable Velocity Change

The rocket equation gives the ratio of the initial mass to the final mass given a velocity change and an exhaust velocity.

$$\frac{m_i}{m_f} = e^\frac{\Delta V}{V_e}$$

This seems to say that given enough fuel we could get an infinite velocity change! To see what the maximum possible velocity change could be we need to account for the structural fraction. The structural fraction multiplied by the mass of fuel gives the mass of the structure needed to support and contain the fuel. The rocket equation now is as follows

$$\frac{m_h + (1+f)m_p}{m_h + fm_p} = e^\frac{\Delta V}{V_e}$$

where $m_p$ is the mass of propellant, $f$ is the structural fraction, and $m_h$ is the mass of all other hardware. If we let the mass of propellant go to infinity, and solve for the velocity change, we get:

$$\frac{\Delta V}{V_e} = \log{\frac{1+f}{f}}$$

The following plot shows the ratio of velocity change to exhaust velocity for a range of structural fractions.

Landing on the Moon

There is a lot of interest in lunar landing missions for both scientific exploration and commercial purposes. Commercial applications might include mining helium-3 for future nuclear fusion power plants on earth and mining water for rocket fuel.

The Spacecraft Control Toolbox makes it easy to do preliminary planning for lunar missions. In this blog we present a single MATLAB script that takes a spacecraft from a low Earth parking orbit to the lunar surface! Here is the final segment, the descent to the moon.

We ended up with a 30 kg dry mass for a spacecraft that can use an ECAPS 220 N HPGP thruster for delta-v.

The published script can be found here:

Lunar Mission Planning as a published MATLAB script

You can also send us an email to find out more about our Lunar Mission Design Tools.

Attitude Maneuvers with the CubeSat Control System

The CubeSat control system is designed to work with either thrusters or reaction wheels. It has a number of handy built in maneuver modes such as pointing at the sun, nadir pointing or pointing at a specific latitude and longitude on the ground. Here is the spacecraft shown in the VisualCommander interface.

The movie in the link below shows attitude maneuvers in the VisualCommander interface. The interface has pages for the various subsystems and attitude control system functions. We start by seeing the spacecraft in a polar orbit on the Summary page. The solar arrays are reorienting themselves so that their cell faces are pointed at the sun. We switch the 3D display to look along the boresight of the telescope. We then go to the ACS page and select a sun pointing maneuver. We go back to the Summary page and see that the sun appears in the display. We then return to the ACS page and command nadir pointing. The remainder of the movie shows the reorientation maneuver to nadir pointing.

For more information on our simulation frameworks including our real-time control system framework, ControlDeck, go to Simulation Framework page.

You can also send us an email to find out more about our CubeSatControl System. All of these products are available now.

Why Use Princeton Satellite Systems’ MATLAB Toolboxes?

Almost all aerospace organizations have extensive libraries of software for simulation, design and analysis. Why then should they use our MATLAB toolboxes?

I’ve been working in the aerospace business since 1979. My experience includes:

1. The Space Shuttle Orbiter Dynamics Analysis
2. The GPS IIR control system design
3. The Inmarsat 3 control system design
4. The GGS Polar Platform control system design
5. The Mars Observer delta-V control system
6. The Indostar-1 control system
7. The ATDRS momentum management system
8. The PRISMA formation flying safe mode guidance

Kepler Telescope Reorientation Maneuver

The Kepler telescope has suffered the loss of two reaction wheels. This means that it cannot use the wheels to control orientation about all three axes.

One option is to use thrusters and reaction wheels at the same time as actuators. Princeton Satellite Systems Core GN&C Bundle does just that.

We’ve simulated the system for the Kepler spacecraft

You can see a movie of a reorientation here:

Direct Fusion Drive Mars Mission – Deep Space Habitat

Check out our new banner! We modified our spacecraft to use NASA’s Deep Space Habitat:

Image Source: NASASpaceFlight

The habitat has a 500 day configuration, with more than enough room for all of the astronauts and their supplies!

We will use the Orion spacecraft for transfer from Earth’s surface to Earth orbit, where it will dock with the DFD powered spacecraft.  That is what the banner image is portraying! Once the astronauts are aboard the DFD powered spacecraft, they will travel to Mars and back in roughly 10 months, including a 1 month stay at Mars.  After they have returned to Earth orbit, the spacecraft will dock with the Orion capsule. The crew can then safely return to Earth’s surface aboard the Orion!

Princeton Plasma Physics Laboratory Inventor’s Dinner

Gary and I attended the Princeton Plasma Physics Laboratory (PPPL) Inventors dinner at Prospect House on the Princeton University campus. Awards were given for 19 patents, patent applications and invention disclosures by PPPL engineers and scientists along with their co-inventors from other institutions.

Gary and I are on a patent application with Sam Cohen of PPPL and Yosef Razin of PSS titled, “Method to Produce High Specific Impulse and Moderate Thrust from a Fusion-powered Rocket Engine: (ARE-Aneutronic Rocket Engine). This is the core technology for our Direct Fusion Drive (DFD). PSS has licensed this and one other fusion patents from Princeton University for DFD work.

I gave a short speech talking about how DFD may take astronauts to Mars in the not too distant future for both orbital and landing missions. We handed out Mars candy bars and DFD bookmarks to the guests.

The dinner was excellent and it was fun talking with our colleagues at PPPL! We look forward to next years dinner!

Is that a spaceship in your pocket?

I remember the day my dad brought home our very first VCR. It was a glorious invention. No longer were our family outings constrained by the TV Guide. This nifty VCR would magically record our favorite shows and allow us to play them back whenever we wanted. It wasn’t long before we had a cabinet full of unlabeled tapes — most of which were never watched again, except while searching for something we accidentally recorded over. But still, it was cool.

That first day, my dad and I watched “The Empire Strikes Back”. Twice! Being just five years old, this was my first “real” movie. I remember in the opening scenes, the huge imperial star destroyer floating ominously across the screen. It seemed to go on forever. Okay, so this is a spacecraft.

Fast forward 32 years. Everything seems to have gotten… smaller.

We can now manage our DVR, record our own digital movies, tweet, text and call from that little smartphone in our pocket. And those huge spaceships from 1980’s fiction? They are now about the size of that first VCR.

We’ve recently designed a 6U CubeSat capable of escaping Earth orbit, rendezvousing with an asteroid, and returning to Earth. Its called “Asteroid Prospector”. It’s shape is 12 x 24 x 36 cm, which is about 5 x 10 x 15 inches, and it weighs about 40 lbs. In other words: its a 1981 VCR. But it goes a lot faster.

Earth departure spiral for the Asteroid Prospector

The Asteroid Prospector is propelled through space using a Busek Bit-3 ion thruster. It uses electric power to accelerate ions out the nozzle at high speed, pushing the spacecraft in the opposite direction of the ion stream. This gives us a small thrust of 1.9 mN, but it can operate for nearly 3 years on just 5 kg of propellant! We are presenting the spacecraft design, mission analysis and example asteroid rendezvous simulations at the upcoming SmallSat conference.

Fast forward another 32 years. Is that a spaceship in your pocket?