Interstellar

Starships are usually imagined as gigantic contraptions. This is a guarantee they'll never be undertaken. Instead, the author proposes a "starship" with a weight of 3-8 kg and the payload of 250-750 g. 

Propulsion is performed by the following ingenious mechanism. While radioactive decay is symmetric over the solid angle, geometric placement of the fissile material (e.g. Am-241 or Pu-240) can be achieved in such a way that the decay products from a tablet of such material in the direction of the motion of the spaceship will be reabsorbed in the elements of the construction. On the contrary, the decay products in the direction of motion will be emitted predominantly into free space. Reaction force then will accelerate the vehicle. 

Fission alone cannot achieve anywhere near a few percent of c needed for the interstellar travel. Yet, the ship will have the sails made of Pd foil saturated with D, T or He3 or a Li6 foil. Fast particles, which are produced by the fission reaction will (with some probability) produce fusion in the asymmetric sails. Again, the sails (author presumes) can be built is such a way that a net recoil from a fusion reaction will be directed along the acceleration path. 

The space system thus constructed can be made so cheap that the swarm of these vehicles with AI-divided tasks between them can accomplish investigation of the planetary system (almost) as successfully as a large probe. 

The payload (similar to the Coke can) will have microscopic actuators to tighten or slacken the wires to the sails. Because the maximum thrust of the contraption is expected to be on the order of a fraction of a newton, the actuators to direct the ship need not be particularly strong. Of course, acceleration/deceleration of such ship is more or less stochastic. 

Prior art: 1) Suggestions of L. Alvarez (one of the fathers of US hydrogen bomb and asteroid hypothesis for the Jurassic collapse) to use fission of transuranium elements emitting into gas jet for space propulsion. 

2) Tritium based initiators for nuclear explosions. 

3) Stochastic micromachines or nanobots. 

Unsolved problem: the communication of the data back to Earth from another planetary system. When the apparatus reaches the nearest stars with planetary systems (in 150-400 years; no reason to be worried of obsolescence--Voyager is now 37 years old), there will be need to transmit the data to the Earth if anyone will still be there to listen with the transmission system weighting on the order of 150-250 g and the available energy on the order of a few watts. 

Expandable bed for long waiting at the airports

Problem: In case of postponed flights passengers have to wait days in the giant airports without possibility to relax. 

Solution: small, low expandable bed, which can be easily fitted to the backpack.

Prior Art: US Army expandable beds. 

Concentration of gamma radiation for medical purposes

Problem: in the absence of lenses for gamma rays, radiation therapy damages outlying tissues. Large doses become problematic.

Solution: use geometric discrimination to filter gamma rays propagating in select directions. Isotope core has a form of a tablet; system of metallic concentric cones attenuates radiation except for propagating in approximately paraxial direction.

Prior Art: Coded mask techniques in gamma-ray astronomy.

Garbage combustion system

Problem: Combustion of garbage creates a lot of poisonous gases.

Solution: produce most of oxidation of carbon in superheated steam. If necessary, coal dust can be added to garbage to ensure correct proportion of carbon vs. hydrogen and oxygen in given batches. Use catalytic oxidation of CO to boil water. Use produced, filtered and Thomson-cooled components of the Wassergas (primarily, mixture of H2, CH4 and nitrogen) for energy production.

System of automated traffic

Problem: current systems (Google-mobile) take too much computer resources and have very complex algorithms to imitate human driving.

Solution: microwave-absorbing bar codes on cars, lorries, road and road signs. Millimeter-wave or terahertz radars instantly ascertain vehicles and distances. Allow automated driving only on specially prepared highways.

Efficient harvesting of the wind energy

Problem: Current windmill-type designs are inefficient, dangerous for the birds and low-flying aircraft, etc.

Solution: replace the propeller blades with stacks of airfoils. Lift of the wind gusts raises and lowers the airfoils. Horizontal displacement is transferred into rotational motion required by the dynamo by a simple mechanical device not so different from the automatic winding devices of mechanical watches used in recent past.

Put RFID Tags on Everything

Problem: We spend time looking for our valets, switched-off cell phones and, especially, all sort of keys.

Problem solved: put RFID tags on everything and design a simple, low-energy consuming RFID ping transmitter. 

Fire Escape for the Dog Cage

Formulation of the problem: Dogs left in the cage at home cannot escape in case of fire or other disaster.

Problem solved: Install temperature or any other (for instance, smoke) sensor in the self-opening lock of the cage. In case of fire, etc. the lock opens and the dog can escape into surroundings. 

Combating Street Flooding with Flood Water

Problem: Sandbags are heavy, require a lot of manual workforce to deploy and limited in their numbers against the rising flood.

Problem solved: Have the pavement equipped with standard slots for temporary steel rod dam holders. Use waterproof pre-weighted tarp-plastic bags to hold the water pumped from the flood waters through the filters. Use synthetic nets to keep water-filled bags in place.