One of the biggest concerns people have with electric vehicles is charging. We’ve taken our Mach-E on two trips with different approaches to charging. Our experience is with a rear-wheel drive Mach-E with the extended range battery. Its EPA range is 303 miles.

The first was from Princeton to the Berkshires, then to Boston and then back to Princeton. The trips were made without any charging on the way. We used Level 2 chargers at our destinations. The Williams Inn, in Williamstown, had ChargePoint chargers, as did the Cambridge Marriott in Kendall Square in Cambridge, MA. At the Cambridge Marriott, there are ChargePoint chargers in the garage used by the valets. The valets are willing to plug your car in as long as you have a ChargePoint card.

The picture blow shows our current mileage.

The most recent trip was from Princeton to Pittsburgh. The one-way distance of 330 miles necessitated charging on the road. We used the Ford app, which showed two stops. We didn’t follow its plan. Instead, we broke the trip into two segments each way with one charging stop. Prior to the trip we tested the high power charging at a local EVGo station.

In both directions we stopped at the Electrify America charging station at 1098 Harrisburg Pike in Carlisle. It was only 2 miles from the highway at a location with the Sheetz convenience store. There were two 350 kW chargers and two 150 kW chargers. Here is the station on the way to Pittsburgh.

It took about 20 minutes to charge from 30% to 80%. We charged until Apple Maps said we had 20% battery margin at our destination. In both directions we ended up with about 15% margin. In Pittsburgh we did destination charging at the Forbes Tower garage. The garage was $22 for 24 hours and charging was free. It was a short walk from the Residence Inn.

On the way to Pittsburgh we were joined at the charging station by two Ford F-150 Lightning trucks. On the way back, we were joined by another Mach-E.

The Electrify America stations were seamless. We have 250 kWh of free charging from Ford. The station knew all about the free charging and we didn’t have to pay or do anything else to be reimbursed. It was simply plug and charge.

PlugShare was the most reliable way to find charging stations.

We drove a Tesla Model 3 as a Hertz rental In Chicago. We charged once at a SuperCharger. It worked very well! I’d say the Electrify America experience was its equal.

For orbital transfers to Mars, a Hohmann transfer is often proposed since it minimizes the fuel consumed. Here is what that looks like.

This was generated by the Spacecraft Control Toolbox function DVHoh.m. 255.2 days is a long time for a crew to be exposed to cosmic radiation. NASA has proposed using a nuclear thermal engine to speed things up. The best combustion engines, like the RL10B-2, use hydrogen and oxygen and have a specific impulse of 465 seconds. This is obtained by running them hydrogen-rich. Nuclear thermal, which is only heating hydrogen, can reach 900 seconds. The higher your specific impulse, the less fuel you use for a given velocity change.

A mission to Mars consists of an Earth escape segment, a heliocentric segment, and Mars entry. You can do them all with the same rocket or use separate stages or methods. For example, you could depart from low-Earth orbit (LEO), do the transfer, and enter low-Mars orbit (LMO) with one stage. As an alternative, the launch vehicle could take the Mars transfer vehicle into a heliocentric orbit. Instead of using the transfer stage to do a powered entry into Mars orbit, you could use aerobraking. Aerobraking could be used, in theory, for both Mars entry and to replace the burn into Mars heliocentric orbit (that is, to match the heliocentric velocity of Mars).

We wrote a MATLAB script in the Spacecraft Control Toolbox to explore some of these concepts. Here are the results:

Specific impulse nuclear thermal 900.00
Specific impulse H2/O2 465.00
Tank Fraction 0.10

Time Hohmann 255.23 days
Time Fast Transfer 150.23 days

Mass fraction Nuclear Thermal Hohmann 0.30
Mass fraction Nuclear Thermal Fast 0.12
Mass fraction H2/O2 Hohmann 0.05
Mass fraction H2/O2 Lambert Only 0.03

Total Delta-V Hohmann 9.03 km/s
Delta-V Hohmann 4.41 km/s

Total Delta-V Fast Transfer 14.35 km/s
Delta-V Fast Transfer Lambert 9.73 km/s
   Departure 4.43 km/s
   Arrival 5.30 km/s
Delta-V Earth Escape 3.19 km/s
Delta-V Mars Entry 1.43 km/s

The Tank Fraction is the fraction of the spacecraft’s dry mass that is proportional to the fuel mass. This is composed mostly of fuel tanks. The mass fraction is how much mass is left when the spacecraft reaches Mars, not including the fuel tanks. The total Delta-V assumes one stage is used to go from LEO to LMO. Lambert’s law is used for the fast transfer. We break up the Lambert maneuver into departure and arrival velocity changes. In principle, you could aerobrake 5.3 km/s + 1.43 km/s.

The fast transfer is shown below. Contrast it with the Hohmann transfer.

This was generated using the Spacecraft Control Toolbox function, PlanetTransferLambert.m.

I’ll be attending two conferences in Europe this September. The first is HiSST, the 2nd International Conference on High-Speed Science and Technology, 11-15 September in Bruges, Belgium. Our paper is “Rotational Detonation Engine for Hypersonic Flight.” My co-authors are
Dr. Christopher Galea, Mr. Miles Simpkins, Dr. Yiguang Ju, and Dr. Mikhail Shneider. The last three authors are from Princeton University. The conference is organized by CEAS, the Council of European Aerospace Societies. We are in session 1a on September 12.

The next conference is the International Astronautical Congress (IAC) in Paris, France 18-22 September. We are presenting the paper, “Nuclear Fusion Powered Titan Aircraft,” with co-authors Annie Price, Zoe Koniaris, Dr. Christopher Galea, Stephanie Thomas, Dr. Samuel Cohen, and Rachel Stutz. Annie will give the presentation. Dr. Samuel Cohen is the inventor of the reactor discussed in the paper and works at the Princeton Plasma Physics Laboratory.

My first overseas conference was IAC in Paris in 1982. I was working at Draper Laboratory at the time.

IAC is also famous from the movie, “2001: A Space Odyssey.” While on Space Station V, Heywood Floyd is asked by Elena, “Well, I hope that you and your wife can come to the I.A.C. conference in June.” To which he replies, “We’re trying to get there. I hope we can.”

After the conference, I’m heading to Aix-en-Provence to visit ITER, where a new experimental Tokamak is under construction. A Tokamak is a toroidal fusion reactor.

Please get in touch with me if you will be at any of the conferences or at ITER!