This is a conceptual design study for a heavy explorer class of starships. This class is based on ideas proposed by the group and a series of driving assumptions. The resulting craft is a large, capable, mobile research platform with enough personnel and resources to adequately explore a star system. It is also rather large, slow, and expensive. Hopefully this can be used as a draft design for group debate and refinement.

Design Assumptions

The assumptions are:

Crew Habitation area - shielding and artificial gravity.
Crew food mass numbers -

Primary Drive System

Multi-cycle RAIR - This system was the original one I suggested for the Explorer class starship design. It used a modified ramscoop that would scoop up fuel launched by a launchers orbiting in our solar system, and scoop up interstellar reaction mass. Unfortunately we don't know what's in interstellar space to scoop up, and current assumptions would suggest that there is to little to bother with.

Externally Fueled Fusion - This system was the final and current one I suggested for the Explorer class starship design. Launchers orbiting in our solar system launch fuel to it to power it during its acceleration out of our solar system, and it would need to carry enough fuel to decelerate it into the target starsystem.

Overview of all concepts

The Externally fueled Fusion rocket concept is a solid baseline design. It violates no rules of physics, and doesn't require any dramatic new technologies to work. So for the rest of the discussion of this Explorer Class of starships we will assume it is the drive system in use. However this system would require the construction of a massive space based fuel launcher and the mining of incredible amounts of fusion reactor fuel, so it would be very expensive.

More important to the assumptions of the LIT group, this drive system is not capable of near relativistic flight. It probably can't get to any faster then 1/4th to 1/3rd of light speed. That means that it isn't suitable for a mission to Tau Ceti (the reference mission under study by L.I.T.) since it would take 30 to 40 years to get there. Which is far to long for a ship as 'small' as an Explorer class, and probably far to long for practical use.

Power Requirements

As you probably already gathered. This ship will need a lot of fuel to accelerate. Oh, for the purpose of this illustration I'm going to create a constant called a Ship_g. A normal g is 9.8 m/s^2. (Meters per second, per second) I like round numbers, so Explorer class ships will accelerate at 10 m/s^2. The crew and ship won't care much, but it makes for much better numbers.

Assuming we're go to accelerate to 1/3rd of light speed (100 million meters per second, a.k.a. 1. E8 m/s). At 1 Ship_g (10m/s^2) our ship will take. E7 seconds to get to speed. That's 115.7 days or about 16.5 weeks. All that time its out accelerating a Corvette (The Explorer class starship has a 0-60mph time of 2.7 seconds.). All that time the home fuel launchers are sending us care packets of fuel. How much fuel?

To accelerate a 25,000,000 ton loaded ship at 10m/s, with a fusion engine with a specific impulse of 2,500,000 we will need to 'burn' about 10 TONS! of fusion fuel per second! You'll need 100,000,000 tons (that's a hundred million tons!) of fuel to accelerate it up to 1/3rd light speed. Frankly, I don't know where we could find that much!

Ships Manifest

Crew support manifest

crew (700)

100 kg per person 70 tons


40 tons per person 28,000 tons Standard food and supplies for 24 years

13 tons per person 9,100 tons Emergency rations for 16 years

Personal effects

10 tons per person 7,000 tons

Hab. deck

structure and buildings 14,000 tons

Shielding 70,000 tons


128,170 tons

Exploration Equipment Manifest

Vacuum landers

200 tons each 4,000 tons 20 vac craft included

Aero landers

200 tons each 2,000 tons 10 aero landers included

Orbital Reconnaissance Satellites

2 tons each 80 tons Set of 40

Long endurance Aerial reconnaissance drones

5 tons each 200 tons Set of 40

Drone rovers

2 tons each 120 tons Set of 60

Heavy Manned rovers (crew of 5)

30 tons each 900 tons Set of 30

Heavy Engineering /mining equipment

2,000 tons


9,300 tons

Starship Total Mass numbers

Exploration Equipment 9,300 tons
Crew, habitation deck, &;Habitation Supplies 60,000 tons
Habitation deck shielding 70,000 tons
Starship Structural Mass (not including engines and Hab deck) 160,000 tons
Engine and drive systems 200,000 tons

Ship dry weight total

500,000 tons
Deceleration Fuel mass (50 to 1 ratio) 25,000,000 tons

Note the last number. Twenty five million tons of fusion isotope. If we use lithium 6 as the fuel isotope. We know that the fuel is a solid stiff metal. So we wont need any fuel tanks. We know that 7.42% of mined Lithium is the isotope we want (which is fortunate since we will need a lot of it.), and that the fuel isotope weights 462 Kilograms per cubic meter. So the 25 million tons, will take a tank with 54 million cubic meters of volume to hold it. If we use a cylindrical tank 200 meters in diameter with a central access shaft 50 meters in diameter. The resulting tank will be 1839 meters long. (We might want a wider shorter starship.)

Diameter Pi * r2
tank 200 31,416 m2
shaft 50 1,963 m2
total 29,452 m2
Tank length for 54 e6 m2 volume 1,839 meters

Explorer class Flight and Mission profile.
Description of the Bussard fusion reactor system used as the refference power system for the ship..


The Explorer Class of starships is the oldest and the most detailed of the designs. Developed by the group. It was my design for a basic fusion powered starship with all the support structures food consumption, habitation deck, and the rest. Worked out in as much detail as we can manage. Its maximum speed is probably only about 1/3rd of light speed, and it can only get to that speed with the equipment to mine millions of tons of fusion isotopes, and a external fuel launcher system. So it wouldn't be fast enough to get to Tau Ceti in an acceptable amount of time (thou quite acceptable for a flight to Alpha Centuri or other near by stars). But it does seem to be a workable starship design, that doesn't require any technologies that don't seem possible within the next 50 years.

APPENDIX 1: Relativity

The time dilation effect (almost all other relativistic effects have a similar equation) is defined as:

t' = t/SQRT(1 - beta^2)

Where t' is the time aboard the ship and t is time to a relatively stationary observer (like Earth), or vice versa since it's a matter of reference whether the ship moves away from the Earth or the Earth moves away from the ship. beta is velocity in terms of light speed (v/c). This basically defines a curve that shoots up to infinity at a beta = 1.

Here are some values for the time dilation factor as a function of speed:

Speed Dilation Factor .09c 1.00407 .19c 1.01855 .29c 1.04490 .39c 1.08599 .49c 1.14715 .59c 1.23856 .69c 1.38158 .79c 1.63104 .89c 2.19317 .99c 7.08881


A book published by NASA in the mid '70's on space colonization. Basically, NASA's take on the old L-5 society's ideas. A light technical book written for the general public that covers all the basics from colony construction, space based industrial processes, launching lunar materials, mass flows within the life support / agricultural system, and psycological effects of different colony shapes. Lots of illustrations, graph, the works.

For Further Information

Reference (1) was on sale (back when originally published) by the Government Printing Office. Their address, for inquiries, is:

     Superintendent of Documents
     Government Printing Office
     Washington, D.C.  20402
     Stock number  033-000-00669-1 
     Catalog number NAS 1.21:413

Also, Bussard and Jameson have formed a company to pursue development of the QED fusion concept. For further information, they can be reached at:

R. W. Bussard &; L. W. Jameson Energy/Matter Conversion Corp. 9100A Center St. Manassas, VA 22110

AIAA papers can be gotten from:

American Institute of Aeronautics and Astronautics 370 l'Enfant Promenade, SW Washington, D.C. 20024

mail me