RASCAL

RASCAL (Responsive Acess Small Cargo Affordable Launch) is a DARPA project to develop a system to cheaply launch small payloads of around 75 Kg to LEO using a reusable high-speed air-launch and expendable rocket. RASCAL is somewhat similar of to SSTT, and in fact the air-launch vehicle could be very useful for SSTT.

RASCAL is developing a very fast airplane they call their first stage. The second stage is a rocket that is 258 Kg empty and has 1865 Kg fuel. This is very close to the size of rocket in the SSTT concept here. RASCAL has a third stage that is 537 Kg total mass of which 50 to 100 Kg is payload. In the proposal here the tether is the third stage and everything the second stage can carry is payload. The table below has more comparisons.

Feature Rascal SSTT Tradeoff
Flight rate 10/year 14/day SSTT can do reusable
First stage High Speed Aircraft Proteus or RASCAL Above atmosphere or cheaper vehicle
Second stage Rocket Reusable rocket Just fuel instead of new rockets
Third stage Rocket Tether Higher operating costs or higher initial costs
Circularize orbit Rocket Aerobreaking/Space Tug Expendable vs Reusable
Development costs $50 mil? $500 mil? New aircraft/rocket vs new rocket/tether
Price per launch $750,000 $50,000 Reusable costs less per launch
Payload to orbit 75 Kg 250+ Kg As tether gets bigger and faster rocket carries more
Payload costs to LEO $20,000/Kg $50/Kg Reusable is far cheaper
Market Small Large Lower cost gets bigger market

RASCAL links

RASCAL - high speed air launch
RASCAL - 50 Kg or more at $20,000 per Kg or less

Feature	Rascal	SSTT	Tradeoff
Flight rate	10/year	14/day	SSTT can do reusable
First stage	High Speed Aircraft	Proteus or RASCAL	Above atmosphere or cheaper vehicle
Second stage	Rocket	Reusable rocket	Just fuel instead of new rockets
Third stage	Rocket	Tether	Higher operating costs or higher initial costs
Circularize orbit	Rocket	Aerobreaking/Space Tug	Expendable vs Reusable
Development costs	$50 mil?	$500 mil?	New aircraft/rocket vs new rocket/tether
Price per launch	$750,000	$50,000	Reusable costs less per launch
Payload to orbit	75 Kg	250+ Kg	As tether gets bigger and faster rocket carries more
Payload costs to LEO	$20,000/Kg	$50/Kg	Reusable is far cheaper
Market	Small	Large	Lower cost gets bigger market